H G Vivien

A Aguichine

O Mousis

M Deleuil

E Marcq

On the Stability of Low-mass Planets with Supercritical Hydrospheres

Keywords: Unified Astronomy Thesaurus concepts: Exoplanet astronomy (486), Exoplanet structure (495), Exoplanet

Short-period, low-mass water-rich planets are subject to strong irradiation from their host star, resulting in hydrospheres in a supercritical state. In this context, we explore the role of irradiation on small terrestrial planets that are moderately wet in the low-mass regime (0.2-1 M ⊕ ). We investigate their bulk properties for water content in the 0.01-5% range by making use of an internal structure model that is coupled to an atmosphere model. This coupling allows us to take into account both the compression of the interior due to the weight of the hydrosphere and the possibility of atmospheric instability in the low-mass regime. We show that, even for low masses and low water content, these planets display inflated atmospheres. For extremely low planetary masses and high irradiation temperatures, we find that steam atmospheres become gravitationally unstable when the ratio η of their scale height to planetary radius exceeds a critical value of ∼0.1. This result is supported by observational data, as all currently detected exoplanets exhibit values of η smaller than 0.013. Depending on their water content, our results show that highly irradiated, low-mass planets up to 0.9 M ⊕ with significative hydrospheres are not in a stable form and should lose their volatile envelope.

Introduction

Earth-like-mass planets represent the ultimate goal of exoplanet detection [START_REF] Kaltenegger | [END_REF]. With today's facilities, their observed number is ever increasing, requiring efforts to enable their characterization, that is, accurate measurement of their mass and radius. Due to their small orbital periods, many of those planets are highly irradiated by their parent stars, implying the need to develop dedicated interior and atmosphere models to investigate their structure and evolution (Mousis et al. 2020;Acuña et al. 2021;Aguichine et al. 2021). In addition, better understanding of the evolution of the hydrosphere of such planets is key to investigating their potential habitability conditions.

In this study, we investigate the bulk properties of highly irradiated, low-mass planets in the 0.2-1 M ⊕ range, and with water content varying between 0.01% and 5%. These water content values roughly bracket the water mass fraction (WMF) estimated for the Earth and Jupiter's moon Europa, respectively.

This mass range is also close to that found by dynamical simulations investigating the formation of water-rich, habitable planets (Raymond et al. 2007). These mass and water content ranges have not been properly quantified so far in the literature because conventional models (e.g., Zeng et al. 2016Zeng et al. , 2019;;Turbet et al. 2019) describe the internal structures of planets with thick atmospheres, neglecting the combination of two important effects: (i) the compression of the interior due to the weight of the hydrosphere, and (ii) the possibility of atmospheric instability at low planetary masses. While the latter can be overlooked for temperate planets, it is critical for high irradiation temperatures and sub-Earth masses. To overcome this issue, we use a self-consistent model in which the atmosphere is coupled with the interior.

Model

Upgrades

The model used here is built upon that described in Aguichine et al. (2021), and includes two major improvements. First, the grid from which the atmospheric properties are interpolated has been extended to surface gravities as low as 1 m s -2 , coupled with a revised convergence scheme. In the new convergence scheme, the atmosphere's properties are updated only when the interior model has stabilized. This revision greatly reduces the occurrence of numerical instability in extreme cases, when planetary mass and radius values are close to the boundaries of the considered range, ensuring convergence to the solution. Second, the atmosphere model now includes a module which assesses the hydrostatic stability of water-rich atmospheres at given planetary mass. This new and improved version expands the operational validity range toward lower masses and smaller WMFs. The model now allows the computation of atmospheres for planets with gravities (g b ), masses, and boundary temperatures in the ranges 1 g b 30 m s -2 , 0.2 M p 20M ⊕ , and 750 T b 4500 K.

Principle

Our model assumes a planet composed of differentiated layers with various compositions including an iron-dominated core, a lower mantle, an upper mantle, and a fluid (from solid to near-plasma) water layer (Mousis et al. 2020;Aguichine et al. 2021). The top of the hydrosphere is a water-dominated atmosphere that follows the prescriptions of Marcq et al. (2017Marcq et al. ( , 2019) ) and Pluriel et al. (2019). The structure of the planets assumes hydrostatic equilibrium and adiabatic heat transfer, and takes into account radiative transfer in the atmosphere to generate its physical properties. By doing so, our model self-consistently takes into account the compression of the internal layers of the planet which results from the presence of a hydrosphere.

Three parameters set the distribution of all chemical species in the different layers of the interior model: the fraction of alloy in the core f alloy , the overall Mg/Si ratio of the planet, and the amount of iron present in the silicate mantle Mg Once defined, the input parameters allow for the computation of the planet's internal structure and associated boundary radius. The atmosphere model provides the outgoing longwave radiation, albedo, thickness, and mass of the atmosphere as a function of the bulk mass and radius, and T b . The atmospheric vertical profile is assumed adiabatic until the temperature drops to the skin temperature T 0 = T eff /2 1/4 , and isothermal above (Marcq et al. 2017(Marcq et al. , 2019)). We choose P 20 tr = mbar as the pressure of the transiting radius, which corresponds to the altitude where the opacity of the atmosphere is close to unity. Summing the atmosphere's mass and thickness with the bulk values yields the final mass M p and radius R p of the planet. The mass of the water present in the atmosphere is computed by integrating its density profile, and is taken into account in the total water content of the planet. While the mass of the atmosphere is typically much smaller than the planet itself (∼0.01%), this correction is crucial for planets with low WMFs.

The interior and atmosphere modules are connected at a given boundary pressure P b = 300 bar, which corresponds to the transition between the vapor and supercritical phases. This threshold is computed for each planet, and thus provides us with an accurate determination of the surface pressure P surf exerted on the refractory layers. Similarly, the temperature at the bottom of the atmosphere T b is computed iteratively for an input irradiation temperature T irr , leading to a true surface temperature T surf .

Stability Criterion

To determine the minimum mass at which a water atmosphere remains stable, we fix a criterion derived from analytical considerations. Modeling the atmosphere beyond P tr as a simple theoretical extended isothermal atmosphere 4 of temperature T irr , the pressure at infinity would be expressed as (Catling & Kasting 2017)

P P GM m kT R exp , 1 tr p irr p = - ¥ ⎜ ⎟ ⎛ ⎝ ⎞ ⎠ ( )
where G is the gravitational constant, k is the Boltzmann constant, and m is the mass of the molecule composing the atmosphere (here H 2 O). This pressure is small but finite, and must correspond to the particle density in the interplanetary medium (IPM), namely n

P kT IPM IPM irr =
, for the atmosphere to be gravitationally bounded. If the value of P ∞ is smaller than P IPM , then the atmosphere contracts in order to reach the expected IPM pressure, and stabilizes. In the opposite situation, the atmosphere escapes from the planet via the Parker wind mechanism (Wang & Dai 2018). Combining the inequality P ∞ > P IPM with Equation (1), we derive a criterion for an atmosphere to be unstable:

H R , 2 p h > ( )
where

H kT R GM m irr p 2 p =
is the planet's height scale, and

ln P P 1 tr IPM h = - ( ) is a dimensionless parameter. If H/R p is larger
than η, the atmosphere is considered hydrostatically unstable.

Because the atmosphere loses its mass by Parker wind in a finite timescale, the value of η in Equation ( 2) is in fact underestimated. However, computing the timescale of atmospheric loss would require a level of modeling that is beyond the scope of this paper. Instead, we estimate η from the output of our model, which can then be used as a conservative estimate of the stability likelihood of a planet.

Investigated Ranges

In this study, the compositional parameters f alloy , Mg/Si, and Mg# of the different mineral layers are assumed to be equal to 0.13, 1.131, and 0.9, respectively. These values correspond to those derived for the Earth (Sotin et al. 2007;Brugger et al. 2017;Aguichine et al. 2021). To determine the impact of the water content on both the mass-radius relationships and the internal structure of low-mass planets, the WMF of our interior model has been set to three different values, namely, 0.01%, 1%, and 5%.

The irradiation temperature T irr is explored in the 500-2000 K range, which essentially covers the domain of irradiation temperatures of exoplanets discovered so far. Because a change in the core mass fraction is expected to impact both the planet's surface gravity and atmospheric structure, three CMF values have been chosen in our simulations, namely, 0, 0.325, and 0.7. These CMF values correspond to the cases of rocky planets, Earth-like planets (Sotin et al. 2007), and Mercury-like planets (Stacey 2005;Benz et al. 2007), respectively. Our computation grid follows a logarithmic mass distribution in the 0.2-1.0 M ⊕ range and linear in the 1.0-2.3 M ⊕ range, but only planets possessing hydrostatically stable atmospheres are shown. This mass range was previously unavailable as the model from Aguichine et al. (2021) could hardly compute the structure of planets of masses below 0.5 M ⊕ . Note that the minimum mass of 0.2 M ⊕ has been chosen because it roughly corresponds to the smallest detectable mass today (see Figure 1 of Deleuil et al. 2020).

Results

Figure 1 shows the planetary radii (scaled in Earth radii) as a function of planetary mass and irradiation temperature. This radius corresponds to the altitude where the pressure reaches P 20 mbar tr = in the hydrosphere. The columns correspond to CMF values of 0, 0.325 and 0.7, respectively. The rows correspond to WMF values of 5%, 1%, and 0.01% respectively. The different panels of the figure cover a mass range where the atmosphere is in hydrostatic equilibrium. In each panel, the upper left corner exhibits a boundary between hydrostatically stable and unstable planets, which depends on the adopted CMF and WMF values. Panels with smaller CMF and higher WMF, which result in lower bulk densities, have more planets with unstable hydrospheres.

In most cases, the planetary radius increases with irradiation temperature and decreases with planetary mass, as an effect of the competition between thermal energy and gravitational binding. This also indicates that the planetary radius is dominated by the atmosphere's thickness. For planets with low water content (i.e., bottom panels of Figure 1 showing WMF = 0.01%), the radius increases with mass when M p ∼ 0.5 M ⊕ . This indicates a regime where the planetary radius is less sensitive to the atmosphere's thickness. Sharp corners in the boundary between stable and unstable planets (e.g., top panels at T irr ; 1500 K and M p ; 0.3 M ⊕ , or middle row at T irr ; 1400 K and M p ; 0.25 M ⊕ ) are visual artifacts caused by the finite resolution of the grid from which atmospheric properties are interpolated. With infinite precision, more points would be available between these corners. Therefore, this edge values that represent pure mantle (0.0), Earth-like (0.325), and Mercury-like (0.7), respectively. Top, middle, and bottom rows correspond to water mass fraction (WMF) values of 5%, 1%, and 0.01%, respectively. The missing data correspond to cases excluded from our calculations due to hydrostatic instability. corresponds to cases that are closest to the physical boundary between stable and unstable atmospheres.

Figure 2 shows the ratio H/R p as a function of planetary mass and irradiation temperature. Contours of constant H/R p values seem parallel to the boundary between stable and unstable atmospheres. The highest computed values of H/R p indicate that η is ;0.1 for our model, and has no apparent correlation with the CMF or the WMF. This value is almost ∼3-4 times higher than the theoretical estimate (η = 0.026-0.035) found for T irr = 500-2000 K, P tr = 10 -3 -20 mbar, and n IPM = 5 × 10 6 m -3 (Catling & Kasting 2017). In the currently confirmed population of exoplanets,5 assuming pure H 2 O atmospheres, we find that H/R p is mainly in the 10 -3 -10 -2 range for planets with masses smaller than 2.3 M ⊕ . Using Kepler-51 b's planetary parameters derived by Masuda (2014), we also find that this planet exhibits one of the highest H/R p values (0.013 0.010 0.006 -+

), which is consistent with the aforementioned 10 -3 -10 -2 range. Even if the assumption of a pure steam atmosphere is likely to be unrealistic, this computation gives an upper bound to the criterion. This value is most certainly an observational limitation; better detection capabilities will allow us to constrain more precisely the boundary between stable and unstable atmospheres based on the H/R p criterion. A similar criterion was derived by Owen & Wu (2016) for planets with a pure H/He envelope, based on the ratio between the planet's radius and its Bondi radius (R p /R B = 2H/R p ). Interestingly, the authors also found that the atmosphere is lost over a short timescale when this ratio exceeds 0.1. Fossati et al. (2017) did a similar study using the restricted Jeans escape parameter Λ = R p /H for H/He-rich planets and found that the atmosphere becomes unstable under a value estimated to be ∼15-35 (equivalent to the previous criterion R p = 0.1R B ). Planets with Λ values as low as 10 (H/R p  0.1) are present in our panels. [START_REF] Cubillos | [END_REF] achieved a similar result and concluded that for the few low-mass planets that exhibit Λ values as low as 10, it is likely that either their mass is underestimated or their radius is overestimated. For this latter case, the possible presence of aerosols in the atmosphere would increase its opacity, and lead to an overestimated transit radius (Wang & Dai 2019;Gao & Zhang 2020;Ohno & Tanaka 2021).

Figure 3 shows mass-radius profiles extracted from Figure 1, and calculated in the cases of three CMF values, assuming WMF = 5% and T irr = 500 K. This figure illustrates the fact that an increase of the CMF increases the surface gravity, and as a consequence reduces the size of the hydrosphere at fixed planetary mass. Even in the case of moderately wet planets (WMF ∼ 5%), the pressure at the bottom of the hydrosphere can easily reach the gigapascal range. The subsequent compression of the interior is no longer negligible, and leads to an increase of the surface gravity. This induces thinner atmospheres, for which the blanketing effect is more moderate.

To illustrate the implications of the H/R p boundary criterion, we estimate the maximum WMF as a function of planetary mass and temperature. For each value of M p and T irr we fit the planetary radius as a function of the WMF with a power-law function to derive a simple relationship between R p and the WMF. We then set H/R p = 0.1, and compute the maximal radius using

H kT R GM m irr p 2 p =
. Finally, we invert the fitted radius-to-WMF relation to compute the theoretical maximum WMF that can be achieved. Results are presented in Figure 4, and show that the stability criterion of the atmosphere strongly limits the amount of H 2 O that can be present in low-mass planets.

To quantify the feedback of the hydrosphere on the interior and the resulting radius, Figure 5 compares our results to those obtained by Turbet et al. (2020). These authors used a predefined interior model from Zeng et al. (2016) coupled with their own atmospheric model. In this comparison, T irr is set to 500 K, and corresponds to 10.38 times the solar insolation received by the Earth. The mass-radius relationships from Zeng et al. (2016) are computed at a surface pressure of 1 bar, and become inappropriate for the modeling of wet planets, since the bottom of the hydrosphere can reach up to 10 GPa. This leads to the contraction of the refractory interior of up to 4% with a WMF of 5%. In turn, this contraction induces a slight increase of the surface gravity that reduces the atmosphere's thickness. The two effects add up to produce a difference in planetary radii of up to ∼10%. For negligible water content, both models yield similar results.

When comparing the hydrospheres alone, our model exhibits thinner hydrospheres than that of Turbet et al. (2020) in most cases. An additional cause of this could be the use of the steam tables from [START_REF] Haar | NBS/NRC steam tables thermodynamic and transport properties and computer programs for vapor and liquid states of water in SI units[END_REF], which encounter several limitations. The corresponding data points can be safely extrapolated up to 3 GPa and 2500 K, but the pressure and temperature at the bottom of the hydrosphere are mostly above this limit (up to ∼4500 K and 10 GPa). As a result, the adiabatic gradient cannot be extrapolated precisely, leading to an isothermal profile. Under those conditions, the density is overestimated, meaning that the radius is underestimated. In our model, we also use the steam tables from [START_REF] Haar | NBS/NRC steam tables thermodynamic and transport properties and computer programs for vapor and liquid states of water in SI units[END_REF] to compute the atmosphere's structure. However, we switch to the equation of state from Mazevet et al. (2019) at P b = 300 bar (supercritical layer). Thanks to this, all equations of state remain in their respective domains of validity within the investigated temperature and pressure ranges. However, given the complexity of both models, it is difficult to list all sources of deviation and precisely quantify their effect. This also highlights the necessity of using identical and up-to-date equations of state when comparing the outcomes of interior models elaborated by different groups.

Conclusion

We have explored the role of irradiation on small terrestrial planets that are moderately wet in the low-mass regime (0.2-2.3 M ⊕ ). To that purpose, we have investigated their bulk properties for water content varying between 0.01% and 5% using an upgraded interior and atmospheric structure model based on that described in Aguichine et al. (2021). The upgrade of this model includes (i) an extension of the grid of atmospheric properties to gravities down to 1 m s -2 , and (ii) an assessment of the hydrostatic stability of water-rich atmospheres at given planetary mass. This coupling allows us to take into account both the compression of the interior due to the weight of the hydrosphere and the possibility of instability of the water layer in the low-mass regime.

Our results show that the compression of the interior should indeed be taken into account to derive proper planetary structure. In the investigated 0.2-2.3 M ⊕ mass range, the pressure is found to be in the 0.03-10 GPa range at the bottom of the hydrosphere, depending on the adopted WMF. This causes the refractory part to contract by up to ∼4% in the explored parameter range. The uncompressed case would corresponds to a typical Earth-like atmosphere with a 1 bar pressure at its bottom. Despite this compression, even for low masses and low water content, the irradiation causes these planets to display inflated atmospheres and increased planetary radius. We also find that the combination of low planetary masses and high irradiation temperatures induces gravitationally unstable steam atmospheres. These planets are subject to rapid atmospheric loss when their H/R p exceeds ;0.1. This value is consistent with the H/R p values found in the population of detected exoplanets, which are mostly smaller than 0.01. We finally point out that, according to our model, some planets with H/R p values suggesting rapidly escaping H/ He atmospheres could in fact be water-dominated planets [START_REF] Cubillos | [END_REF]Wang & Dai 2019;Gao & Zhang 2020;Ohno & Tanaka 2021).

Interestingly, the mass limit below which the atmosphere is unstable in our simulations could shift toward larger masses if thermal escape is considered. Given the high irradiation temperatures, thermal escape can lead to a complete loss of the whole hydrosphere (Lopez & Fortney 2013;Owen & Wu 2013;Kurosaki et al. 2014;Lopez 2017;Aguichine et al. 2021). This supports the idea that highly irradiated, low-mass planets with thick hydrospheres should not be common, as they lack gravitationally stable atmospheres. O.M. and M.D. acknowledge support from CNES. We also extend our thanks to the anonymous referee for their insight and useful comments.

ORCID iDs

H. G. Vivien https:/ /orcid.org/0000-0001-7239-6700 A. Aguichine https:/ /orcid.org/0000-0002-8949-5956 E. Marcq https:/ /orcid.org/0000-0002-1924-641X

  which describes the level of differ- entiation of the planet. Two required compositional inputs of the model are the planet's core mass fraction (CMF) and WMF. Pressure and temperature profiles are integrated from the outside, and require the inputs of the boundary pressure P b and the boundary temperature T b . Finally, the model also requires the input of the planet's mass M b (subscript b denotes the mass encapsulated within the boundary of the interior model, and excludes the atmospheric contribution).

Figure 1 .

 1 Figure 1. Computed planetary radii R p at the transiting depth P 20 mbar tr = as a function of planetary mass M p and irradiation temperature T irr . Contours show lines of constant planetary radii (in units of Earth radius) to improve the readability of each panel. Left, center, and right columns correspond to core mass fraction (CMF)values that represent pure mantle (0.0), Earth-like (0.325), and Mercury-like (0.7), respectively. Top, middle, and bottom rows correspond to water mass fraction (WMF) values of 5%, 1%, and 0.01%, respectively. The missing data correspond to cases excluded from our calculations due to hydrostatic instability.

Figure 2 .

 2 Figure 2. Similar to Figure 1, but with a color scheme representing the H/R p contours.

Figure 3 .

 3 Figure 3. Mass-radius relationships calculated for three CMFs, WMF = 5% and T irr = 500 K. Dotted and solid lines correspond to the base and the top of the hydrosphere, respectively.

Figure 4 .

 4 Figure 4. Maximum WMF as a function of planetary mass and irradiation temperature predicted by our model for CMF values representing mantle-like, Earth-like, and Mercury-like interiors. All WMFs are calculated assuming H/ R p = 0.1, and using a power law fitted to our results. Contours represent different WMF values. For example, the gray region corresponds to planets fully made of water.

Figure 5 .

 5 Figure 5. Comparison between the mass-radius relationships computed from our model (red, blue, and purple solid lines) and that of Turbet et al. (2020) (red, blue, and purple dotted lines) for T irr = 500 K and CMF = 0. Both models define the transiting radius as the altitude where the opacity is close to unity. The colored and black dashed lines correspond to the base of the hydrosphere computed from our approach and that of Turbet et al. (2020), respectively.

The AstrophysicalJournal, 931:143 (7pp), 2022 June 1 https://doi.org/10.3847/1538-4357/ac66e2 © 2022. The Author(s). Published by the American Astronomical Society.Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

Gravity variation is taken into account.

The Astrophysical Journal, 931:143 (7pp), 2022 June 1 Vivien et al.

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Comparaison of continuous wave transscleral cyclophotocoagulation versus two micropulse transscleral cyclophotocoagulation protocols (standard and high energy) in refractory glaucoma patients

Walid Bougamha

A mes maîtres chirurgiens

Le Docteur David Martiano, j'ai toujours apprécié ta bonne humeur. Tu as toujours su te montrer disponible et m'apporter des conseils avisés. Merci pour la formation et les connaissances que tu m'as apporté. On se retrouve cet été pour une session Rollers avec Caro ! Le Docteur Benjamin Butet, tu es un chirurgien hors-pair, et j'ai beaucoup appris à tes côtés.

Je garde de très bons souvenirs de mon internat grâce à toi ! (promis pas de combat de lutte ce soir)

Le Docteur Jacques CHOFFLET, merci pour vos conseils avisés, votre enseignement en ophtalmologie et surtout pour votre bonne humeur permanente.

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Table des matières

INTRODUCTION

Glaucoma is a progressive optic neuropathy characterized by a loss of retinal ganglion cells, cupping of the optic nerve and visual-field defects (1). Several etiologies have been reported

(2), and most of them have in common an elevation of the intraocular pressure (IOP).

Treatment is mainly based on IOP decrease. IOP lowering eyedrops are usually the first line treatment. In certain circumstances, surgical treatment may be required. Filtering surgery, although being the gold standard, is not ideal [START_REF] Razeghinejad | A History of the Surgical Management of Glaucoma[END_REF]. Beyond its failure rate over the long term [START_REF] Allbon | Cyclodiode Laser Glaucoma Therapy[END_REF],it has been associated with sight threatening complications also such as choroidal detachment, chronic hypotony, endophthalmitis, or loss of the point of fixation in agonic glaucoma [START_REF] Bloom | Cyclodiode[END_REF]. Therefore, new surgical and less invasive procedures have emerged.

Transscleral cyclophotocoagulation (TC) has initially been developed for the treatment of refractory or agonic glaucoma [START_REF] Liu | Mechanism of intraocular pressure decrease after contact transscleral continuous-wave Nd:YAG laser cyclophotocoagulation[END_REF]. TC consists in partial ciliary body destruction by delivering 810 nanometers wavelength laser targeting the melanin contained in the ciliary epithelium and ciliary stroma [START_REF] Vernon | Diode laser cycloablation in adult glaucoma: longterm results of a standard protocol and review of current literature[END_REF]. This results in a decrease in aqueous humor secretion and therefore subsequent IOP. An increase in aqueous humor drainage through the uveoscleral tract has also been evoked [START_REF] Vernon | Diode laser cycloablation in adult glaucoma: longterm results of a standard protocol and review of current literature[END_REF]. Initially, TC was performed in a continuous wave delivery (TC-CWD) fashion. However, TC-CWD has been associated with several side effects related to excessive ciliary process heating such as persistent postoperative hypotony and even phtysis bulbi [START_REF] Liu | Mechanism of intraocular pressure decrease after contact transscleral continuous-wave Nd:YAG laser cyclophotocoagulation[END_REF][START_REF] Kosoko | Long-term outcome of initial ciliary ablation with contact diode laser transscleral cyclophotocoagulation for severe glaucoma. The Diode Laser Ciliary Ablation Study Group[END_REF][START_REF] Ishida | Update on results and complications of cyclophotocoagulation[END_REF][START_REF] Quigley | Improved Outcomes for Transscleral Cyclophotocoagulation Through Optimized Treatment Parameters[END_REF][START_REF] Ma | Micropulse laser for the treatment of glaucoma: A literature review[END_REF]. Recently, micropulsed transscleral cyclophotocoagulation (TC-MP) has been developed

to reduce the postoperative side effects, aiming at treating patients earlier during glaucoma progression [START_REF] Varikuti | Outcomes of Micropulse Transscleral Cyclophotocoagulation in Eyes With Good Central Vision[END_REF][START_REF] Tan | Micropulse transscleral diode laser cyclophotocoagulation in the treatment of refractory glaucoma[END_REF]. TC-MP consists in repetitive micropulses of active diode laser (ON-cycle) separated by rest intervals (OFF-cycle). OFF-cycles is thought to allow thermal dissipation from tissues, thus avoiding excessive heating, reducing pain and subsequent side effects [START_REF] Aquino | Micropulse versus continuous wave transscleral diode cyclophotocoagulation in refractory glaucoma: a randomized exploratory study[END_REF].

Previous studies have demonstrated that TC-MP was an effective procedure against refractory glaucoma, with a favorable safety profile [START_REF] Aquino | Micropulse versus continuous wave transscleral diode cyclophotocoagulation in refractory glaucoma: a randomized exploratory study[END_REF][START_REF] Emanuel | Micropulse Cyclophotocoagulation: Initial Results in Refractory Glaucoma[END_REF][START_REF] Kuchar | Treatment outcomes of micropulse transscleral cyclophotocoagulation in advanced glaucoma[END_REF][START_REF] Williams | Clinical Efficacy and Safety Profile of Micropulse Transscleral Cyclophotocoagulation in Refractory Glaucoma[END_REF][START_REF] Lee | Outcome of Micropulse Laser Transscleral Cyclophotocoagulation on Pediatric Versus Adult Glaucoma Patients[END_REF][START_REF] Habash | Outcome Of MicroPulse® Transscleral Photocoagulation In Different Types Of Glaucoma[END_REF][START_REF] Zaarour | Outcomes of Micropulse Transscleral Cyclophotocoagulation in Uncontrolled Glaucoma Patients[END_REF][START_REF] Tekeli | Comparative efficacy and safety of micropulse transscleral laser cyclophotocoagulation using different duration protocols in eyes with good visual acuity[END_REF][START_REF] Preda | Clinical outcomes of micropulse transscleral cyclophotocoagulation in refractory glaucoma-18 months follow-up[END_REF]. However, two major questions remain unsolved. First, the ideal TC-MP protocol and subsequent energy delivery is still debated.

Energies delivered with TC-MP are comprised between 60J and 190J [START_REF] Emanuel | Micropulse Cyclophotocoagulation: Initial Results in Refractory Glaucoma[END_REF][START_REF] Lee | Outcome of Micropulse Laser Transscleral Cyclophotocoagulation on Pediatric Versus Adult Glaucoma Patients[END_REF][START_REF] Zaarour | Outcomes of Micropulse Transscleral Cyclophotocoagulation in Uncontrolled Glaucoma Patients[END_REF][START_REF] Preda | Clinical outcomes of micropulse transscleral cyclophotocoagulation in refractory glaucoma-18 months follow-up[END_REF][START_REF] Yelenskiy | Patient Outcomes Following Micropulse Transscleral Cyclophotocoagulation: Intermediate-term Results[END_REF][START_REF] Sanchez | Micropulse Transscleral Cyclophotocoagulation: A Hypothesis for the Ideal Parameters[END_REF]. The higher the energy is delivered, the better the IOP decreases but with increasing side effects. procedures, in patients with refractory glaucoma.

PATIENTS AND METHODS

Study design and participants

A retrospective comparative and multicentric study was conducted. Data from patients treated for refractory glaucoma were collected from January 2010 to October 2021 at the University Hospital of Nice and Cannes hospital, France. All the patients with refractory glaucoma who underwent a TC-CWD or a TC-MP procedure were screened. Refractory glaucoma was defined as an IOP greater than 21 mmHg despite maximal medical treatment with or without prior glaucoma surgery and regardless the type and progression of glaucoma. Patients with initial IOP below 21 mmHg, or with a follow-up < 3 months were excluded.

Surgical protocol

TC-MP and TC-CWD procedures were performed under general anesthesia or local anesthesia with intravenous sedation in an output patient setting. Postoperatively, all patients were instructed to continue their topical IOP lowering medications until reexamination. For TC-MP procedures, the energy delivered was calculated as follows: Joules (J) = power (W) x total treatment duration (s) x duty cycle (31.3%). For TC-CWD procedures, the energy delivered was calculated as follows: Joules (J) = power (W) x time exposure per burn (s) x number of burns.

TC-MP was performed by using the Cyclo G6 laser system (IRIDEX; CYCLO G6 Glaucoma Laser System, Mountain View, CA, USA) with a P3 probe. TC-MP was performed by trained surgeons at the University hospital of Nice between July 2020 and October 2021. Briefly, the probe was applied firmly at the limbus over the conjunctiva and moved in a continuous sliding arc motion (painting motion) in superior and inferior quadrants avoiding the 3 and 9 o'clock meridians. The device was set with 0.5 ms ON-time and 1.1 ms OFF-time corresponding to a duty cycle of 31.3% as recommended by the manufacturer. Two groups were compared, based on the power and duration settings used.

-TC-MPSE was performed according to the manufacturer recommendations with a "standard energy" (SE) calculated as follows: power = 2500mW, duration = 50 s per hemifield, corresponding to a total energy delivered of 78.25 Joules.

-TC-MPHE delivered a higher energy (HE): power = 2000mW, duration = 110 s per hemifield, corresponding to a total energy delivered of 137 Joules.

After TC-MP procedure, patients were prescribed topical Dexamethasone phosphate 0.1% three times a day for ten days and topical Indomethacin three times a day for one month.

TC-CWD procedure was performed by one trained surgeon at the Cannes hospital between January 2010 and October 2021. Under general anesthesia, the G probe (CW-TSCPC, Iris Medical Instruments, Mountain View, CA) was placed axially with its footplate at the edge of the limbus. Laser settings used were 2000mW, 2 sec exposure time per burn, 20 burns per eye delivering 80 Joules per treatment. The power was decreased when audible "pops" were heard, and laser energy delivery was adjusted. At the end of the procedure, patients were prescribed topical Dexamethasone phosphate 0.1% four times a day for ten days.

Data and follow-up

The following data were recorded: age, sex, type of glaucoma, previous treatments, number of glaucoma medications, best-corrected logMar visual acuity, initial IOP, cup-to-disk ratio. IOP was measured using Goldman applanation tonometry. Complications including hyphema, corneal oedema, prolonged inflammation, hypotony, phtysis, scleral thinning and major ocular hypertension were recorded. Hypotony was defined as an IOP below 8 mmHg during the follow-up. Phtysis bulbi was defined as persistent hypotony associated with globe volume loss.

Major ocular hypertension was defined as an increase greater than 30% from baseline IOP.

Prolonged inflammation was defined as an anterior chamber inflammation beyond one month after treatment.

Primary and secondary endpoints

The primary endpoint was defined as an IOP decrease ≥ 30% from baseline IOP at 3 months.

The secondary outcomes included the number of IOP lowering medications, the complications and the need for retreatment (with another cyclodestruction procedure or another glaucoma treatment) at 1 month, 3 months, 6 months, 9 months and 12 months.

Statistical analysis

Descriptive statistics are presented as numbers and percentages for categorical variables.

Analyzes were performed using Chi2 to compare qualitative, and ANOVA tests and student T tests to compare quantitative data, respectively with SPSS software (IBM, Chicago, Illinois, USA). A p value <0.05 was considered as statistically significant.

The mean number of IOP-lowering drugs throughout the follow-up is shown in Figure 3. The mean number of IOP medications significantly decreased at 1 month (p=0.01) but did not at 3 months (0.07), 6 months (p=0.16), 9 months (p=0.23) and 12 months (p=0.16). At 3 months, the mean number of IOP-lowering drugs was reduced in all groups (-0.9 in the TC-CWD group, -0.8 in the TC-MPSE group and -2.5 in the TC-MPHE group) without any statistical difference between groups (p=0.06).

The results of the primary endpoint are shown in Table 2. The primary end point (IOP decrease ≥ 30% at 3 months) was fulfilled in 13 eyes (62%) in the TC-CWD group, in 3 eyes (33%) in the TC-MPSE group, and in 4 eyes (50%) in the TC-MPHE group. Overall, 20 eyes out of 38 (53%) achieved the primary outcome measure, without any significant differences between the groups (p=0.35).

The prognosis factors are presented in Table 3. Only neovascular glaucoma (NVG) was significantly associated with an increased risk of treatment failure (p=0.01).

Retreatments are shown in Table 4. At 3 months, 7 eyes (33%) in the TC-CWD group, 5 eyes (55%) in the TC-MPSE group, and 3 eyes (37%) in the TC-MPHE group needed retreatment.

No statistical difference was found between the groups (p=0.824). At 3 months, 4 eyes (19%) in the TC-CWD group, 5 eyes (55%) in the TC-MPSE group, and 4 eyes (50%) in TC-MPHE group had an IOP≥ 21mmHg still (Table 4).

The postoperative complications are presented in

DISCUSSION

In this study, we compared the efficacy and safety of TC-CWD versus 2 different energy TC-MP protocols in patients with refractory glaucoma. All the procedures were efficient to reduce the IOP (-22.8% to -34.9% depending on the procedure) without sight-threatening complications.

Efficacy of the procedures

In the TC-CWD group, 62% of the eyes reached an IOP decrease ≥ 30% at 3 months with a mean IOP lowering of 10.6mmHg (-34.9%). Our results are better than those reported by Aquino et al. [START_REF] Emanuel | Micropulse Cyclophotocoagulation: Initial Results in Refractory Glaucoma[END_REF] who found a success rate of 30% after TC-CWD. This difference could be explained by the fact that their success criteria was tighter (≥ 30 of IOP-lowering and IOP between 6 and 21 mmHg) than those of our study (Table 5).

In the TC-MPSE group, 33% of the eyes reached an IOP decrease ≥ 30% at 3 months with a mean IOP lowering of 7.7 mmHg (-22.8%). Our results are consistent with prior studies: Tan et al. [START_REF] Aquino | Micropulse versus continuous wave transscleral diode cyclophotocoagulation in refractory glaucoma: a randomized exploratory study[END_REF] by using a 62 Joules TC-MP procedure reported an IOP decrease of -31% at 3 months.

In the TC-MPHE group, 50% of the eyes reached an IOP decrease ≥ 30% at 3 months with a mean IOP decrease of 7.8 mmHg (-24.4%). Zaarour et al. [START_REF] Tekeli | Comparative efficacy and safety of micropulse transscleral laser cyclophotocoagulation using different duration protocols in eyes with good visual acuity[END_REF] found an IOP decrease of 23.9% at 3 months using a 113 Joules TC-MP procedure, which is nearly consistent with our results. Tekeli et al. [START_REF] Preda | Clinical outcomes of micropulse transscleral cyclophotocoagulation in refractory glaucoma-18 months follow-up[END_REF] reported a higher success rate of 77.3% (mean IOP lowering of 40.2%) at 3 months by using an higher energy (150 Joules) protocol (Table 5).

In our 3 groups, NVG appeared to be a significant pejorative prognostic factor (p=0.01). Tan et al. [START_REF] Aquino | Micropulse versus continuous wave transscleral diode cyclophotocoagulation in refractory glaucoma: a randomized exploratory study[END_REF] also reported a higher failure rate in patients with NVG (50%), as did Quigley et al. [START_REF] Ma | Micropulse laser for the treatment of glaucoma: A literature review[END_REF] who showed that the success rate decreased from 79% to 18% in NVG patients. NVG is a widely recognized cause of surgical failure whatever the surgery. The inflammatory cytokines are thought to compromise the bleb formation. Therefore, the use of intraoperative antimetabolites is highly recommended in NVG patients undergoing a trabeculectomy [START_REF] Ramli | Risk factors for hypotony after transscleral diode cyclophotocoagulation[END_REF].

Similarly, the inflammatory cytokines may be involved in the surgical failure of the cyclodestructive procedures by altering the uveoscleral evacuation of the aqueous humor [START_REF] Singh | Diode laser cyclophotocoagulation paves way to a safer trabeculectomy in eyes with medically uncontrollable intraocular pressure[END_REF][START_REF] Liu | Diode laser transscleral cyclophotocoagulation followed by phacotrabeculectomy on medically unresponsive acute primary angle closure eyes: the long-term result[END_REF].

The decreased number of daily IOP-lowering drugs at 3 months was 0.9 in the TC-CWD group, 0.8 in the TC-MPSE group and 2.5 in the TC-MPHE group. Our results are consistent with previous studies (Table 5) [START_REF] Emanuel | Micropulse Cyclophotocoagulation: Initial Results in Refractory Glaucoma[END_REF][START_REF] Zaarour | Outcomes of Micropulse Transscleral Cyclophotocoagulation in Uncontrolled Glaucoma Patients[END_REF][START_REF] Preda | Clinical outcomes of micropulse transscleral cyclophotocoagulation in refractory glaucoma-18 months follow-up[END_REF][START_REF] Yelenskiy | Patient Outcomes Following Micropulse Transscleral Cyclophotocoagulation: Intermediate-term Results[END_REF][START_REF] Sanchez | Micropulse Transscleral Cyclophotocoagulation: A Hypothesis for the Ideal Parameters[END_REF]. In our study, the retreatment rate in the TC-CWD group (33%) and the TC-MPSE group (55%) were similar to those from Aquino et al. (

(Table 5). Our retreatment rate in the TC-MPHE group (37%) is higher than in the literature, which is reported to range from 8% to 20% [START_REF] Lee | Outcome of Micropulse Laser Transscleral Cyclophotocoagulation on Pediatric Versus Adult Glaucoma Patients[END_REF][START_REF] Zaarour | Outcomes of Micropulse Transscleral Cyclophotocoagulation in Uncontrolled Glaucoma Patients[END_REF][START_REF] Preda | Clinical outcomes of micropulse transscleral cyclophotocoagulation in refractory glaucoma-18 months follow-up[END_REF][START_REF] Yelenskiy | Patient Outcomes Following Micropulse Transscleral Cyclophotocoagulation: Intermediate-term Results[END_REF][START_REF] Sanchez | Micropulse Transscleral Cyclophotocoagulation: A Hypothesis for the Ideal Parameters[END_REF]. It could be explained by the fact that other studies used higher energy levels and treated less advanced glaucoma compared to ours [START_REF] Preda | Clinical outcomes of micropulse transscleral cyclophotocoagulation in refractory glaucoma-18 months follow-up[END_REF]. Although no statistical difference was found in terms of retreatment rate in our 3 groups, 2 patients (22%) in the TC-MPSE group required 2 additional glaucoma procedures and 1 patient (11%) required 3 additional procedures while only 1 patient (12%) in the TC-MPHE group required 2 additional procedures. Interestingly, Tekeli et al. [START_REF] Preda | Clinical outcomes of micropulse transscleral cyclophotocoagulation in refractory glaucoma-18 months follow-up[END_REF] showed that the retreatment rate after TC-MP decreased from 37.5% to 15.9% when the energy increased from 100 to 150J (p<0.001).

Safety profile of the procedures

No case of phtysis bulbi was recorded in our study. Only one case (5%) of long-term hypotony (< 8mmHg at last follow-up) was observed in the TC-CWD group. The patient had a NVG and received an 84 Joules TC-CWD procedure. This observation is in accordance with previous reports highlighting the increased risk of hypotony in NVG patients undergoing cyclophotocoagulation (29). Surprisingly, Aquino et al. [START_REF] Emanuel | Micropulse Cyclophotocoagulation: Initial Results in Refractory Glaucoma[END_REF] experienced much more side effects than in our study, further reporting 1 case of phthisis bulbi (4%), 5 cases of prolonged hypotony (23%), 17% of scleral thinning, and 30% of prolonged anterior chamber inflammation (beyond 3 months) in the TC-CWD group. These differences could be explained by a higher rate of NVG patients (50% of NVG versus 23% in our study), a longer follow-up (18 months), and a potential higher energy used (88-106 Joules per treatment vs 79,5 Joules in our study).

No sight-threatening complications were observed in the TC-MP groups, confirming the safety of this procedure when used with an energy below 140 Joules. Williams et al. [START_REF] Lee | Outcome of Micropulse Laser Transscleral Cyclophotocoagulation on Pediatric Versus Adult Glaucoma Patients[END_REF] investigated the efficacy and safety of TC-MP using a higher mean energy of 187.8 +/-26.2 Joules. They reported 2.5% of phthisis bulbi, 5% of persistent hypotony, 2.5% of corneal edema and 25% of anterior chamber inflammation (≥ 3 months). Sanchez et al. [START_REF] Senthil | Trabeculectomy for neovascular glaucoma in proliferative diabetic retinopathy, central retinal vein occlusion, and ocular ischemic syndrome: Surgical outcomes and prognostic factors for failure[END_REF] performed a literature review and determined that the optimal parameters (benefit/risk balance) for TC-MP was comprised between 110 and 150 Joules.

Major postoperative ocular hypertension (≥ 30% IOP from baseline) was encountered herein in 2 patients and in 1 patient in the TC-MPSE and TC-MPHE groups, respectively. These hypertensive picks were all found at day 1 and spontaneously resolved at day 7. It highlights the need to continue all the postoperative IOP-lowering medications following a TC procedure until the next visits.

Strengths and limitations

Our study is the first, to our knowledge, to compare 3 different TC procedures. Most authors use their own parameters, which may explain the difficulty to compare and analyze the studies from one to another. Therefore, we aimed to standardize our data and previous data based on the energy delivered with each treatment. Limitations of our study include its small sample size, its retrospective design, and the lack of long-term follow-up. For instance, glaucoma severity was not accurately established because not all the patients underwent a preoperative visual field or an RNFL analysis using OCT. This is probably explained by the fact that most patients were sent to our tertiary center for treatment and were then followed-up by their own ophthalmologist. Despite all our efforts to recover all the follow-up data, some of them remained missing which explains the high number of excluded patients. For the same reasons, the mean follow-up was limited, and we chose a follow-up of 3 months to assess TC procedures efficacy. However, as shown in Figure 2, the postoperative IOP seems to decrease over time, which is consistent with other studies in the literature [START_REF] Preda | Clinical outcomes of micropulse transscleral cyclophotocoagulation in refractory glaucoma-18 months follow-up[END_REF].

Pushing forward the indications of TC

In accordance with previous studies, we demonstrated that TC-MP is a simple, micro-invasive, efficient, reliable, and safe procedure. TC procedures, and especially TC-MP, should not be longer being considered as an aggressive procedure with a high risk of prolonged hypotony and phtysis bulbi. In addition, TC procedures provide progressive IOP lowering contrary to filtering surgery, justifying its use in agonic glaucoma. However, TC procedures should not be considered as the "holy grail" because one quarter to a half of the patients will further require retreatment or additional treatment. Further studies focusing on TC retreatments outcomes would be of prime interest. A major drawback in glaucoma is that treatments are often considered as sole, i.e. opposed to each other, and not complementary. Further studies combining TC procedures with others therapeutic strategies would be relevant. TC procedures are thought to lower IOP by decreasing the aqueous humor production: it could be associated with other procedures increasing the aqueous humor evacuation such as the Microinvasive Glaucoma Surgery (MIGS). Despite common belief, associating a TC procedure with a filtering surgery does not result in an increased risk of chronic hypotony or postoperative choroidal detachments. In contrary, several studies claimed for a preoperative TC procedure before performing a trabeculectomy to reduce the preoperative IOP and the subsequent IOP fall. Another critical but unsolved point is the best timing to respect when performing a TC procedure followed by another glaucoma procedure to optimize the success rate.

CONCLUSION

TC-CWD, TC-MPSE and TC-MPHE procedures allowed IOP-lowering ≥ 30% in approximately half of our refractory glaucoma patients. One quarter to a half of patients will require retreatment during the follow-up. Only one case (5%) of chronic hypotony was encountered.

Considering its effectiveness and safety, TC-MP procedures should not be considered anymore as a last line treatment. Further studies investigating the association of TC procedures with other glaucoma treatments such as filtering surgeries or MIGS would be relevant.

FIGURES

  Thèse pour l'obtention du diplôme d'état de Docteur en Médecine Présentée et soutenue publiquement Le vendredi 8 avril 2022 à la faculté de Médecine de Nice Par Monsieur Walid BOUGAMHA Né le 03 octobre 1992 à Nice (06) Spécialité chirurgicale : ophtalmologie Examinateurs de la thèse : Président du jury : Madame le Professeur Stéphanie BAILLIF Assesseurs : Monsieur le Professeur Carl ARNDT Monsieur le Professeur Charles Hugo MARQUETTE Monsieur le Docteur Jacques PAYAN Directeur de thèse : Monsieur le Docteur Arnaud MARTEL Tu m'as fait l'honneur de diriger cette thèse, je te remercie de m'avoir accompagné tout au long de ce travail. Ta pédagogie, tes encouragements, tes conseils et tes corrections m'ont été précieux pour continuer d'avancer. C'est une fierté que d'avoir pu effectuer ce travail sous ta supervision. Ton dévouement pour l'ophtalmologie niçoise force notre respect. Trouve ici le témoignage de mon plus profond respect et de ma plus sincère reconnaissance.

Louis, tu étais

  déjà un super co-interne à l'époque de Pasteur, tu es devenu un très bon rétinologue maintenant ! Plein de bons souvenirs de soirées avec toi ! Laura, merci pour ta bonne humeur ! Ly Chun, Benjamin, Thierry, Baptiste même si nous avons eu peu l'occasion de travailler ensemble vous êtes des co-internes au top. Jérémy & Elsa, je vous souhaite toute la réussite pour l'avenir. Aux équipes soignantes Team Pasteur : Jeff, Véro, Sidonie, Cathy, Marie Angèle, grande Flo, petite Flo, Cécilia, Nadine, Christine, Fabienne, Evelyne, Barth, Aminata, merci pour ces belles années à vos côtés, j'en garde de merveilleux souvenirs ! Mention spéciale à petite Flo et Cécilia que j'ai régulièrement harcelé de mails pour ma thèse et qui ont toujours été ultra réactives pour m'aider à avancer ! Team Cannes : Sandrine, Aude, Fanny, Laetitia, Christelle, Camille, Manu, Laurence, Marion, Mathilde, Marie-Noelle, Caro merci pour tout, j'ai passé une très belle année à Cannes grâce à vous. Zaza & Judes mes antillais adorés, merci pour l'ambiance et les blagues salace à tout va ! Team Reims : Adrien, Charlotte, David, Kevin, Mathieu, Mathilde, Ophélie, Catherine, Jimmy, Justine : Merci pour votre accueil, j'ai passé un super bon semestre grâce à vous ! Léo, David, Dounia, Elena, Marianne, Mériem, LP, Ghiles, Néthanel, Yacine, Veronika, Yazid : un semestre au top avec vous, merci de m'avoir accueilli dans la bonne ambiance rémoise ! Et le meilleur pour la fin, à toi Camille : Ma petite quenouille voilà bientôt deux ans que tu partages ma vie, tu m'apportes énormément de joie et de bonheur au quotidien et tu m'aides à devenir un homme meilleur de jour en jour. J'ai toujours pu compter sur ton soutien et ton amour indéfectible, et tu pourras compter sur le mien. Tu n'as jamais hésité une seconde à me suivre dans mes aventures les plus folles. Notre vie est parfaite, parce que tu es parfaite. J'ai hâte de débuter notre nouvelle vie en Nouvelle-Calédonie.

Figure 1 :

 1 Figure 1: Study Flowchart. .................................................................................................................

Figure 2 :

 2 Figure 2: Mean intraocular pressure during the follow up. ..............................................................

Figure 3 :

 3 Figure 3: Mean number of IOP-lowering drugs. ................................................................................

Sanchez

  et al.[START_REF] Senthil | Trabeculectomy for neovascular glaucoma in proliferative diabetic retinopathy, central retinal vein occlusion, and ocular ischemic syndrome: Surgical outcomes and prognostic factors for failure[END_REF] analyzed the results of various studies and found that the best TC-MP energy associated with the best benefit-risk ratio was comprised between 110 and 150J.Second, data comparing TC-CWD with TC-MP are scarce. To our knowledge, only Aquino et al.[START_REF] Emanuel | Micropulse Cyclophotocoagulation: Initial Results in Refractory Glaucoma[END_REF] compared TC-CWD with TC-MP, further reporting that TC-MP achieved similar IOP decrease with fewer collateral side effects, as compared to TC-MP.The aim of this study was to compare the efficacy and safety of TC-CWD with 2 TC-MP energy delivery modalities, i.e. a standard energy (TC-MPSE) and a high energy (TC-MPHE)

Singh

  et al. (30) investigated the TC-CWD procedure used as a temporary measure for lowering IOP prior performing a trabeculectomy. The mean baseline IOP was 46.5 mmHg (range 38-54). The IOP decreased to 22.8 (± 3.3) mmHg one week after the TC-CWD procedure delivered with a mean energy of 25.2 Joules. Trabeculectomy was performed after an average of 34.3 (±13.2) days and resulted in a final IOP of 16.3 (±1.9) mmHg at 2 years follow-up. Only 1 patient (8%) developed a transient hypotony and choroidal detachment posttrabeculectomy which resolved at day 7. No patients developed persistent hypotony or phthisis bulbi. In case of acute primary angle closure (APAC) refractory to medical treatment, trabeculectomy has been associated with a high risk of failure and complications. Liu et al. (31) investigated the efficacy and safety of TC-CWD followed by phacotrabeculectomy in APAC.The baseline IOP ranged from 43.2 to 58.7 mmHg. After the TC-CWD procedure (mean energy = 85 Joules), the IOP ranged from 23.3 to 32 mmHg. Phacotrabeculectomy was performed between 3 and 10 days after TC-CWD. At final follow-up visit, the IOP ranged from 12.8 to 18 mmHg. No sight-threatening complications were encountered during the follow-up. These studies support the fact that TC procedures may ready the eye for subsequent filtering surgery.

Figure 1 :

 1 Figure 1: Study Flowchart. MP: MicroPulse Transscleral Cyclophotocoagulation; CWD: Continuous Wave Delivery Transscleral Cyclophotocoagulation.

Figure 2 :

 2 Figure 2: Mean intraocular pressure during the follow up. TC-CWD: Continuous Wave Delivery cyclophotocoagulation; TC-MPSE: MicroPulse Standard Energy Transscleral Cyclophotocoagulation; TC-MPHE: MicroPulse High Energy Transscleral Cyclophotocoagulation

Figure 3 :

 3 Figure 3: Mean number of IOP-lowering drugs. TC-CWD: Continuous Wave Delivery cyclophotocoagulation; TC-MPSE: MicroPulse Standard Energy Transscleral Cyclophotocoagulation; TC-MPHE: MicroPulse High Energy Transscleral Cyclophotocoagulation

La team Fréjus Croucroune tu

  as le coeur sur la main, merci pour cette joie de vivre et ces bons souvenirs ! Marie Eve toujours rayonnante de bonté, merci pour tout,

	A mes amis Lucas, mon plus vieil ami, l'époque de la cour d'école est déjà bien loin. Tu es là depuis le
	début sans jamais nous perdre malgré la distance. Je suis heureux que tu partages cet
	événement majeur avec nous ce soir.
	Kévin, mon Bokit ! Le meilleur des réunionnais (ex-aequo avec Ponpon), tu es rapidement
	devenu mon frère de coeur. Je suis très heureux de t'avoir rencontré au début de mon internat
	et d'avoir partagé tant d'aventures avec toi. Sophie est une personne exceptionnelle et vous Anouck, vieille chouette, tu es la rencontre la plus incroyable que j'aurais pu espérer en D4.
	formez un très beau couple. Partout où Cam et moi iront vous aurez votre place auprès de On a été un super binôme de révision. Un grand merci pour tous ces moments de déconnade
	nous. (mais aussi de travail acharné). Je suis content que tu aies pu redescendre dans le sud après
	toutes ses années, passez nous voir pendant notre assistanat qu'on se marre un peu :)
	Caroline Sornay, merci pour ces belles années d'internat où l'on s'est serré les coudes, tu es
	l'une des personnes sur qui je peux compter en toutes circonstances. Tu es dévouée et le
	service d'Ophtalmologie de Cannes a beaucoup de chance de pouvoir compter sur tes talents
	de glaucomatologue.
	Salim & Mohamed, bande de veaux…
	Cela reste des remerciements, je ne pourrai donc pas vous victimiser ici ce soir... mais je n'en
	pense pas moins !
	Merci pour ces belles années passés ensemble. J'ai des bons souvenirs en pagaille, on a
	toujours pu compter les uns sur les autres et se serrer les coudes. Je suis heureux que vous
	ayez trouvé vos voies dans le Sud et que la vie vous comble de ses bienfaits.
	Je descends bientôt, on pourra refaire un week-end avec plein d'activités.
	Momobis Alketbi, je t'ai connu interne puis tu es devenu chef Momo. Tu m'as accompagné
	dès mes débuts en ophtalmologie (« c'est une paupiérite aigüe ! ») et je t'en suis très
	reconnaissant. C'est toujours un plaisir de déconner avec toi !

Riad, merci d'avoir toujours cru en moi. Je sais que l'on peut compter les uns sur les autres et serrer les coudes quand c'est nécessaire. Je te souhaite toute la réussite dans tes futurs projets ! Ryan & Khalil, mes petits neveux adorés, ne grandissez pas trop vite ! A ma belle-famille Rosy, merci pour tous les bons moments passés ensemble et l'énergie positive que tu dégages. Tu as toujours été de bon conseil et j'ai toujours trouvé une oreille attentive auprès de toi. Je suis heureux de te compter dans ma famille. Merci pour ton soutien. Clémychou, toujours aussi rayonnante (avez-vous vu ces fossettes ?). Merci d'être descendu pour ma thèse, je suis très heureux que tu puisses partager ce moment avec nous. Tu es la petite soeur que je n'ai jamais eu ! Guillaume, tu es une personne bourrée de qualités ! C'est toujours un plaisir de passer du temps avec toi. Ravi d'avoir montré à ta maman que même les garçons parlent d'aspirateurs entre eux ! Lise, tu es une personne d'une grande gentillesse et d'une grande sensibilité. Je te souhaite beaucoup de réussite dans ta carrière scientifique. Philippe, merci de m'avoir accueilli dans votre famille. Vous savez toute l'admiration, la confiance et le respect que je vous porte. Camille a beaucoup de chance de vous avoir comme père. Laleh, tu as le coeur sur la main et tu as toujours été bienveillante avec moi. C'est toujours un plaisir de passer du temps avec toi. Merci pour ton accueil chaleureux et ton soutien durant mon internat. Kikou, merci d'être présente en ce jour si important ainsi que tous ces bons moments passés à Lourmarin. Dans la paix, l'harmonie et la Joie ! Roxane & Dara, vous êtes des frères et soeurs géniaux, on déconne toujours bien avec vous. J'espère que l'avenir nous apportera plus de temps tous ensemble. Ken, cochonouuuu !!! On commence à avoir vécu beaucoup de choses ensemble. J'ai toujours pu compter sur toi, tu es une personne sincère et généreuse, toujours le coeur sur la main. Merci pour ton soutien durant ce travail de thèse ! Tu m'as aidé du mieux que tu le pouvais et je ne l'oublierai pas. Fini le VTT, faut aller plus vite : cet été c'est moto-cross de descente, suffit juste que je travaille mes atterrissages ! Passez nous voir pendant l'assistanat! Morgane, hier encore nous étions à l'internat de l'Archet, t'es une personne géniale et je suis très heureux de te voir partager ta vie avec Ken. Hâte d'être à votre mariage !! (J'ai ramené le Tartenfion !) Hatem, tellement de bons moments avec mon deuxième Bokit ! Merci pour ta bonne humeur et ton humour au quotidien, courage pour terminer la Capa ! Marie, la plus fréjussienne de toutes, toujours un plaisir de te voir ! Merci d'être venue ce soir. Justine & Jérôme, voilà déjà une belle paire d'années que l'on se connaît ! Je suis très heureux de clôturer mes études de médecine avec vous. Justine, tu es une personne horspair, d'une gentillesse sans limite. Tu étais présente dès les débuts, tu as toujours été bienveillante avec moi. Jérôme, tu as le coeur sur la main et des qualités que je respecte énormément. C'est toujours un plaisir de passer du temps avec vous, vous formez un merveilleux couple.

Michaud, Aurélie, Kévin R., José & Zézé, Jessica, Thibault, merci

	pour tous ces bons moments passés à Fréjus ainsi que
	tous les moments de rigolade qui ont suivi ! Brazer's & Remy vous êtes au top ! On rigole
	toujours vraiment bien ensemble, bientôt le défi 1000 pompes ! Yan, ta personnalité est
	sincèrement attachante, ne change rien.

La team Colloc' : Mathilde, Gauthier, Cora, Stéphane, Edwige, Flavien, cette

	colloc était
	géniale, merci de m'avoir accueilli auprès de vous ! Merci pour votre bonne humeur et ces
	bons moments passés à vos côtés.
	Caroline Jung, Clément Reynier, la team Marseille ! Vous êtes de très belles rencontres.
	Merci de m'avoir fait (re)découvrir Marseille, je suis très content que vous puissiez être parmi
	nous ce soir !
	Antoine, Roxane, Marion, merci pour ces années de folles aventures durant nos études en
	médecine. J'ai des souvenirs plus incroyables les uns que les autres. Je vous souhaite
	beaucoup de bonheur pour vos vies futures, vous le méritez !
	Loïc (Ponpon), énormément de bons souvenirs avec toi (dont pas mal de soirées
	complètement folles), merci de m'avoir accueilli auprès des tiens à la Réunion et d'avoir fait le
	déplacement pour fêter cet évènement important !
	Arnaud & Camille, Arnaud tu es l'une des personnes les plus déjantées que je connaisse. Et
	j'adore ça ! Camille merci pour ta gentillesse et ta bonne humeur.

Team Cannes : Khadija, Hubert, Adrien, Tiphaine, merci

	pour ces quelques mois de vie
	commune qui ont illuminé mon passage à Cannes !

Arthur, Laurine, Mélina, merci

  d'être présents ce jour, c'est toujours un plaisir de vous voir.

	Florine Broussard, tu es une personne avec énormément qualité. Je suis très content d'avoir
	fait la mission au Togo avec toi !
	Karim, la classe incarnée. Je sais qu'on pourra toujours compter l'un sur l'autre, merci d'être
	parmi nous ce soir.
	A

mes co-internes (ou ancien co-internes devenus chefs) :

	Professeur, j'admire infiniment plus pour tes qualités humaines que ton lever de coude. Même
	si Montpellier restera une merveilleuse soirée ! C'est toujours un plaisir de passer du temps
	avec toi.

  Table des matières ................................................................................................................................ AND METHODS ..................................................................................................................... Study design and participants ........................................................................................................... Surgical protocol ................................................................................................................................ Data and follow-up ............................................................................................................................

ABSTRACT .............................................................................................................................................. RESUME ................................................................................................................................................. INTRODUCTION ..................................................................................................................................... PATIENTS Primary and secondary endpoints..................................................................................................... Statistical analysis .............................................................................................................................. Ethics ................................................................................................................................................. RESULTS ................................................................................................................................................. DISCUSSION ........................................................................................................................................... CONCLUSION ......................................................................................................................................... FIGURES .................................................................................................................................................

TABLE .

 .

....................................................................................................................................................

Table 1: Patients' baseline characteristics ........................................................................................ Table 2: Intraocular pressure and medication number..................................................................... Table 3: Results of the main outcome measures. .............................................................................

Table 4 :

 4 Pronostic factors for success and failure of procedure. ......................................................

Table 5 :

 5

	20

Postoperative side effects ................................................................................................... Table 6: Litterature review ................................................................................................................ REFERENCES .......................................................................................................................................... de la pression intraoculaire (PIO) ≥ 30% à 3 mois après la chirurgie. Les critères de jugement secondaires étaient la diminution en valeur brute de la PIO, le nombre de médicaments hypotonisants, la survenue de complications et la nécessite d'un retraitement. Résultats : Trente-huit yeux (34 patients) ont été inclus. La PIO moyenne initiale était de 31,5 mmHg (SD 7,6, range 21 à 48). Le nombre moyen de médicaments hypotonisants avant la chirurgie était 3,7. Aucune différence statistiquement significative n'a été retrouvée entre les groupes. L'énergie moyenne était de 79,5 Joules pour le groupe TC-CWD (n=21), 76,1 pour le groupe TC-MPSE (n=9) et 137,3 pour le groupe TC-MPHE (n=8). La PIO a significativement diminué au 1 er et 3 ème mois post-opératoire (p=0,04). A 3 mois, 62%, 33% et 50% des yeux des groupes TC-CWD, TC-MPSE et TC-MPHE respectivement ont complété le critère de jugement principal, sans différence statistique entre les groupes (p=0,34). La diminution du hypotonie prolongée (<8mmHg) et 3 patients ont eu un hyphema post-opératoire.

Table 4 .

 4 Five patients experienced major

	ocular hypertension (≥ 30% from baseline IOP) after treatment: one patient in the TC-CWD
	group at six months follow-up which required retreatment with another TC-CWD procedure, 2
	in the TC-MPSE group and 1 in the TC-MPHE group at first day after procedure which
	spontaneously resolved at day 7. Only one eye in the TC-CWD group experienced a long-term
	hypotony (IOP ≤ 8 mmHg) without decrease of his best corrected visual acuity. No patients
	experienced phtysis bulbi. Three patients in the TC-CWD group experienced a postoperative

TABLETable 1 : Patients' baseline characteristics

 1

	BCVA: best-corrected visual acuity; IOP: intraocular pressure; TC-CWD: Continuous Wave
	Delivery cyclophotocoagulation; TC-MPSE: MicroPulse Standard Energy Transscleral
	Cyclophotocoagulation;	TC-MPHE:	MicroPulse	High	Energy	Transscleral
	Cyclophotocoagulation; MIGS: microinvasive glaucoma surgery; POAG: primary open angle
	glaucoma; NS: non-significant; NVG: Neovascular glaucoma; SLT: selective laser
	trabeculoplasty.

(n = 38 eyes, 34 patients).

Table 2 : Intraocular pressure and medication number during the follow-up period.

 2 IOP: intraocular pressure; TC-CWD: Continuous Wave Delivery cyclophotocoagulation; TC-MPSE: MicroPulse Standard Energy Transscleral Cyclophotocoagulation; TC-MPHE: MicroPulse High Energy Transscleral Cyclophotocoagulation

		Bougamha 2022	Tekeli 2021	Preda 2019	Al Habash 2019	Yelenski 2018	Williams 2018	Aquino 2014
	Study design	RMu	RMo	PMo	PMo	RMu	RMo	PMoR
	Mean age (years)	59.3	57.1	62.6	60	73	70.2	58.75
	Study protocol	TC-CWD 79J TC-MPSE 76J TC-MPHE 137J	MP 150J vs MP 100J	4 groups of IOP MP 100J-163J	MP 165J	MP 112-150J	MP 190J	CWD 60-112J MP 62.6J
	Eye number	38	76	100	71	197	79	48
	Mean follow-
	up	9.4	12	18	12	12	7.8	18
	(months)
	Main outcome measure	Reduction IOP ≥ 30%	IOP ≤21 mmHg and reduction IOP ≥ 30%	IOP ≤21 mmHg or reduction IOP ≥ 30%	IOP ≤21 mmHg or reduction IOP ≥ 30%	IOP ≤18 mmHg or reduction IOP ≥ 20%	IOP ≤21 mmHg or reduction IOP ≥ 20%	IOP ≤ 21 mmHg and reduction IOP ≥ 30%
	Mean baseline IOP (mmHg)	TC-CWD:30.4 TC-MPSE:33.7 TC-MPHE:32	150J:31.1 100J:31.3	39.1	35	22	31.9	CWD 35 MP 36.5
	Mean IOP at last follow-up (mmHg)	TC-CWD:20.9 TC-MPSE:24 TC-MPHE:18.2	150J:19 100J:18.5	22.8	16	16	16.3	CWD 19 MP 20

Table 6 :

 6 Litterature review IOP: intraocular pressure; RMo: retrospective monocentric; RMu: retrospective multicentric; PMuR: prospective multicentric randomized; PMo: prospective monocentric; PMoR: prospective monocentric randomized; MP: micropulse group; TC-CWD: Continuous Wave Delivery cyclophotocoagulation; TC-MPSE: MicroPulse Standard Energy Transscleral Cyclophotocoagulation; TC-MPHE: MicroPulse High Energy Transscleral Cyclophotocoagulation

	Success rate	TC-CWD:62% TC-MPSE:33% TC-MPHE:50%	150J:79.5% 100J:75%	93.1%	95.7%	71%	67%	CWD 30% MP 52%
	Mean baseline number of drugs	TC-CWD:3.6 TC-MPSE:3.9 TC-MPHE:3.7	150J:3.1 100J:2.9	2.6	5	3	2.3	CWD 2 MP 2
	Mean number of drugs at last follow-up	TC-CWD:2.7 TC-MPSE:3.1 TC-MPHE:1.3	MP 150J :2.2 MP 100J:2.3	1.8	4	2	0.8	CWD 1 MP 1
	Retreatment	TC-CWD: 33% TC-MPSE:55% TC-MPHE:37%	150J:15.9% 100J:37.5%	20%	11.2%	8%	12%	CWD 54% MP 46%
	Sight threatening complications	TC-CWD:5% hypotony	0	Hypotony 3%	0		-Phtysis: 2.5% -Persistant hypotony: 5%	TC-CWD -Phtysis: 4% -Hypotony: 21%

Acknowledgments: none

Conflict of interest: none

Funding support: none

Le serment d'Hippocrate

"Au moment d'être admis(e) à exercer la médecine, je promets et je jure d'être fidèle aux lois de l'honneur et de la probité.

Mon premier souci sera de rétablir, de préserver ou de promouvoir la santé dans tous ses éléments, physiques et mentaux, individuels et sociaux.

Je respecterai toutes les personnes, leur autonomie et leur volonté, sans aucune discrimination selon leur état ou leurs convictions. J'interviendrai pour les protéger si elles sont affaiblies, vulnérables ou menacées dans leur intégrité ou leur dignité. Même sous la contrainte, je ne ferai pas usage de mes connaissances contre les lois de l'humanité. J'informerai les patients des décisions envisagées, de leurs raisons et de leurs conséquences.

Je ne tromperai jamais leur confiance et n'exploiterai pas le pouvoir hérité des circonstances pour forcer les consciences.

Je donnerai mes soins à l'indigent et à quiconque me les demandera. Je ne me laisserai pas influencer par la soif du gain ou la recherche de la gloire.

Admis(e) dans l'intimité des personnes, je tairai les secrets qui me seront confiés. Reçu(e) à l'intérieur des maisons, je respecterai les secrets des foyers et ma conduite ne servira pas à corrompre les moeurs.

Je ferai tout pour soulager les souffrances. Je ne prolongerai pas abusivement les agonies.

Je ne provoquerai jamais la mort délibérément.

Je préserverai l'indépendance nécessaire à l'accomplissement de ma mission. Je n'entreprendrai rien qui dépasse mes compétences. Je les entretiendrai et les perfectionnerai pour assurer au mieux les services qui me seront demandés. J'apporterai mon aide à mes confrères ainsi qu'à leurs familles dans l'adversité.

Que les hommes et mes confrères m'accordent leur estime si je suis fidèle à mes promesses ; que je sois déshonoré(e) et méprisé(e) si j'y manque."

Material and method:

A multicentric retrospective and comparative study was conducted.

The patients were divided into 3 groups: TC-CWD, TC-MP standard-energy (TC-MPSE), and TC-MP high-energy (TC-MPHE). The primary end point was defined as a reduction of the IOP ≥ 30% from baseline at 3 months after the surgery. Secondary endpoints were the absolute IOP reduction, the number of IOP lowering medications, the side events, and the need for retreatment.

Results: Thirty-eight eyes (34 patients) were included. The mean baseline IOP was 31.5 (SD 7.6, range 21-48) mmHg. The mean number of IOP-lowering medication before surgery was 3.7. No statistical difference was noted between the groups. The mean energy was 79.5

Joules in the TC-CWD group (n=21), 76.1 Joules in the TC-MPSE group (n=9) and 137.3 Joules in the TC-MPHE group (n=8). IOP significantly decreased at 1 month and 3 months post procedure (p=0.04). At 3 months, 62%, 33% and 50% of the eyes fulfilled the primary outcome in the TC-CWD, TC-MPSE and TC-MPHE groups, respectively (no statistical difference, p=0.34). The mean decrease in IOP lowering medications at 3 months was -0.9, -0.8 and -2.5, respectively, without any statistical difference (p=0.06). 33%, 55% and 37% of the eyes needed a retreatment, respectively, without any statistical difference (p=0.82).

Neovascular glaucoma was identified as a risk factor for retreatment (p=0.01) in all groups. In the TC-CWD group, 1 patient (5%) experienced long-term hypotony (<8 mmHg) and 3 patients had postoperative hyphema.

Conclusion:

Our results suggest that all the three transscleral procedures are effective and safe for lowering IOP in patients with refractory glaucoma, although one third to a half of patients require repeated treatments over time.

Ethics

The study protocol met the principles stated in the declaration of Helsinki. Due to its retrospective design, no institutional approval was required.

RESULTS

One hundred and seven eyes of 96 patients were screened. We excluded 69 eyes due to missing data or insufficient follow-up (Figure 1). The study included 38 eyes of 34 patients with a mean age of 59.3 years (SD 20.9, range: 7-88 years). Twenty-one (55%) eyes were included in the TC-CWD group, 9 (24%) eyes in the TC-MPSE group, and 8 (21%) eyes in the TC-MPHE group (Figure 1). Patients' baseline characteristics are presented in Table 1. The mean baseline IOP was 31.5 mmHg (SD: 7.6, range 21-48 mmHg) without significant difference between groups (p=0.56). The mean number of IOP-lowering drugs was 3.7 without any difference between the groups (p=0.85). Primary open angle glaucoma (POAG) and neovascular glaucoma (NVG) were diagnosed in 39% and 21% of patients, respectively.

In the TC-CWD group, the patients were treated with a mean energy of 79.5 Joules (SD: 33.9, range 40-110). In TC-MPSE and TC-MPHE groups, the patients were treated with a mean energy of 76.1 Joules (SD:12.9, range 70-78.2) and 137.3 Joules (SD:22.7, range 110-156.5), respectively. The postoperative IOP is detailed in Figure 2. The IOP significantly decreased at 1 month (p=0.04), 3 months (p=0.04), and 12 months (p=0.01) but did not at day 1 (p=0.82), 6 months (p=0.22) and 9 months (p=0.75). At day 1, the mean IOP was significantly lower in the TC-MPHE group (-43.1%) compared to the other groups (-37.2% in the TC-CWD group and -11.6% in TC-MPSE group, p=0.029). At 3 months, the mean IOP was reduced by 34.9% in the TC-CWD group, by 22.8% in the TC-MPSE group, and by 24.4% in the TC-MPHE group without any significant difference between the groups (p=0.27).