Potential of an Amphiphilic Artificial Corneal Endothelial Layer as a Replacement Option for Damaged Corneal Endothelium.

Bullous keratopathy, a condition severely impacting vision and potentially leading to corneal blindness, necessitates corneal transplantation. However, the shortage of donor corneas and complex surgical procedures drive the exploration of tissue-engineered corneal endothelial layers. This study develops a transparent, amphiphilic, and cell-free membrane for corneal endothelial replacement. The membrane, securely attached to the posterior surface of the cornea, is created by mixing hydroxyethyl methacrylate (HEMA) and ethylene glycol dimethylacrylate (EGDMA) in a 10:1 ratio. A 50 µL volume is used to obtain a 60 µm hydrophobic membrane on both sides, with one side treated with a polyvinylpyrrolidone (PVP) solution. The resulting membrane is transparent, foldable, biocompatible, amphiphilic, and easily handled. When exposed to 20% sulfur hexafluoride (SF6), the hydrophilic side of the membrane adheres tightly to the corneal Descemet's membrane, preventing water absorption into the corneal stroma, and thus treating bullous keratopathy. Histological test confirms its effectiveness, showing normal corneal structure and low inflammation when implanted in rabbits for up to 100 d. This study showcases the potential of this membrane as a viable option for corneal endothelial replacement, offering a novel approach to address donor tissue scarcity in corneal transplantation.

Intradevice Repeatability and Interdevice Comparison of Two Specular Microscopy Devices in a Real-Life Setting: Tomey EM-4000 and Nidek CEM-530.

Background and Objectives: The purpose of this study was to compare two commercially available specular microscopes (Tomey EM-4000 and Nidek CEM-530) in a real-life clinical setting in terms of intra- and interdevice variability. The study was conducted on all patients seen in a clinical practice specializing in anterior segment pathologies, regardless of the purpose of their visit. Materials and Methods: In total, 112 eyes of 56 patients (age 23-85 years old) were included in the study. Each eye was measured three times with each device (for a total of six measurements), and results for central corneal thickness (CCT) and corneal endothelial cell density (ECD) were recorded. The results were then evaluated with the D'Agostino-Pearson normality test and compared with a Wilcoxon signed-rank test, t-test, ANOVA or Mann-Whitney test for intra- and interdevice variability. Results: Both specular microscopes produced very reliable reproducible intradevice results: The Tomey EM-4000 measured an ECD of 2390 ± 49.57 cells/mm2 (mean ± standard error of mean); the range was 799-3010 cells/mm2. The determined CCT was 546 ± 5.104 µm (mean ± standard error of mean [SEM]); the range was 425-615 µm. The measurements with the Nidek CEM-530 revealed an ECD of 2417 ± 0.09 cells/mm2 (mean ± SEM); the range was 505-3461 cells/mm2 (mean ± SEM). The mean CCT detected was 546.3 ± 4.937 µm (mean ± SEM); the range was 431-621 µm. The interdevice differences were statistically significant for both parameters, ECD (p = 0.0175) and CCT (p = 0.0125) (p < 0.05). Conclusions: The Nidek CEM-530 and the Tomey EM-4000 both produced reliable and reproducible results in terms of ECD and CCT. The absolute measurements were statistically significantly different for CCT and ECD for both devices; the Nidek produces slightly higher values.

A Prospective, Randomized, Controlled Clinical Investigation Comparing the Efficacy and Safety of Sodium Hyaluronate-Based Ophthalmical Viscosurgical Devices FIDIAL PLUS and IAL®-F in Cataract Surgery.

Purpose: To protect the corneal endothelium, various ophthalmical viscoelastic devices (OVDs) are used during cataract surgery. In this study, we compared two sodium hyaluronate-based OVD, the bacteria-derived FIDIAL PLUS OVD (test) with the animal-derived IAL®-F OVD (reference) during the surgical procedure. Methods: Fifty patients with bilateral cataract participated in the study: 50 eyes randomly received FIDIAL PLUS and 50 eyes received IAL®-F (ratio 1:1). Noninferior efficacy of FIDIAL PLUS compared with reference OVD (first objective) was evaluated using a paired t-test comparing the mean percent loss of corneal endothelial cells (CECs) with FIDIAL PLUS against the mean percent loss with IAL®-F. Corneal endothelial protection during cataract surgery with FIDIAL PLUS without significant (≥30 mmHg) postoperative intraocular pressure (IOP) increase (main secondary objective) was assessed using a repeated measures logistic model comparing the incidence of significant postoperative IOP elevation between the two groups. Safety, tolerability, and efficacy were also evaluated by assessing secondary endpoints before and after surgery. Results: FIDIAL PLUS showed a statistically noninferior efficacy compared with IAL®-F; there was no significant increase in IOP in either group or different trends of the secondary endpoints were observed between the OVD groups. The safety profile was similar in both OVD groups and no adverse device effects were reported. Conclusions: This study demonstrates the equivalent efficacy, tolerability, and safety of the bacteria-derived FIDIAL PLUS compared with the animal-derived IAL®-F, confirming the clinical value of this product.

A Case of Transparent Cornea Maintained after Removal of Dislocated Graft from Descemet's Stripping Automated Endothelial Keratoplasty.

Introduction: Corneal graft detachment is a major postoperative complication of Descemet's stripping automated endothelial keratoplasty (DSAEK). When a corneal graft becomes detached, corneal endothelial function generally fails, and repeat corneal transplantation is required. Herein, we report a rare case in which a transparent cornea was maintained after the removal of a dislocated DSAEK graft. Case Presentation: A 79-year-old woman with a residual lens cortex who had undergone cataract surgery was referred to our hospital. The cortex was removed, and bullous keratopathy progressed. Six months after the initial surgery, DSAEK was performed under topical anesthesia without any complications. Although the corneal graft had attached fairly well, it detached from the host cornea 3 weeks later. Two months after DSAEK, an air tamponade was used to treat the anterior chamber with single interrupted suturing; however, the graft detached again, except for the suture site. Because the detached cornea became cloudy in the anterior chamber, it was surgically removed 8 months after DSAEK. Accordingly, the host cornea transparency improved to a best-corrected visual acuity of 0.8 with a rigid gas permeable lens and a central corneal thickness of 580 µm. The corneal endothelial cell density was 995 cells/mm2. Conclusion: Removal of the corneal graft from the dislocated cloudy graft improved the visual acuity of this patient after DSAEK. The condition of the cornea should be carefully monitored after corneal endothelial transplantation, even after the graft has been dislocated.

Enhanced Migration of Fuchs Corneal Endothelial Cells by Rho Kinase Inhibition: A Novel Ex Vivo Descemet's Stripping Only Model.

Descemet's Stripping Only (DSO) is a surgical technique that utilizes the peripheral corneal endothelial cell (CEnC) migration for wound closure. Ripasudil, a Rho-associated protein kinase (ROCK) inhibitor, has shown potential in DSO treatment; however, its mechanism in promoting CEnC migration remains unclear. We observed that ripasudil-treated immortalized normal and Fuchs endothelial corneal dystrophy (FECD) cells exhibited significantly enhanced migration and wound healing, particularly effective in FECD cells. Ripasudil upregulated mRNA expression of Snail Family Transcriptional Repressor (SNAI1/2) and Vimentin (VIM) while decreasing Cadherin (CDH1), indicating endothelial-to-mesenchymal transition (EMT) activation. Ripasudil activated Rac1, driving the actin-related protein complex (ARPC2) to the leading edge, facilitating enhanced migration. Ex vivo studies on cadaveric and FECD Descemet's membrane (DM) showed increased migration and proliferation of CEnCs after ripasudil treatment. An ex vivo DSO model demonstrated enhanced migration from the DM to the stroma with ripasudil. Coating small incision lenticule extraction (SMILE) tissues with an FNC coating mix and treating the cells in conjunction with ripasudil further improved migration and resulted in a monolayer formation, as detected by the ZO-1 junctional marker, thereby leading to the reduction in EMT. In conclusion, ripasudil effectively enhanced cellular migration, particularly in a novel ex vivo DSO model, when the stromal microenvironment was modulated. This suggests ripasudil as a promising adjuvant for DSO treatment, highlighting its potential clinical significance.

Sleep deprivation induces corneal endothelial dysfunction by downregulating Bmal1.

BACKGROUND: Sleep deprivation (SD) is a common public health problem that contributes to various physiological disorders and increases the risk of ocular diseases. However, whether sleep loss can damage corneal endothelial function remains unclear. This study aimed to determine the effect and possible mechanism of SD on the corneal endothelium. METHODS: Male C57BL/6J mice were subjected to establish SD models. After 10 days, quantitative RT-PCR (qRT-PCR) and western blot or immunostaining for the expression levels of zonula occludens-1 (ZO-1), ATPase Na+/K + transporting subunit alpha 1 (Atp1a1), and core clock genes in the corneal endothelium were evaluated. Reactive oxygen species staining and mitochondrial abundance characterized the mitochondrial function. The regulatory role of Bmal1 was confirmed by specifically knocking down or overexpressing basic helix-loop-helix ARNT like 1 protein (Bmal1) in vivo. In vitro, a mitochondrial stress test was conducted on cultured human corneal endothelial cells upon Bmal1 knockdown. RESULTS: SD damaged the barrier and pump functions of mouse corneal endothelium, accompanied by mitochondrial dysfunction. Interestingly, SD dramatically downregulated the core clock gene Bmal1 expression level. Bmal1 knockdown disrupted corneal endothelial function, while overexpression of Bmal1 ameliorated the dysfunction induced by SD. Mitochondrial bioenergetic deficiency mediated by Bmal1 was an underlying mechanism for SD induced corneal endothelial dysfunction. CONCLUSION: The downregulation of Bmal1 expression caused by SD led to corneal endothelial dysfunction via impairing mitochondrial bioenergetics. Our findings offered insight into how SD impairs the physiological function of the corneal endothelium and expanded the understanding of sleep loss leading to ocular diseases.

Effect of mitomycin C on the corneal endothelial cells of Saudi patients with myopia after transepithelial photorefractive keratectomy: a two-armed cohort study.

AIM: To study the effect of mitomycin C (MMC) applied during transepithelial photorefractive keratectomy (TPRK) on the corneal endothelium one week (W1) and three months (M3) after surgery and its determinants. METHODS: In this two-armed cohort study conducted in 2022, eyes treated with MMC during TPRK (group 1) were compared with eyes not treated with MMC (group 2). The corneal endothelial cell (EC) count, EC density (ECD; cells/mm2), average (µm2), standard deviation (µm2), coefficient of variation (CV%), ECmax, ECmin, and EC percentage of hexagonality were estimated at W1 and M3. The postoperative changes in the EC count in the two groups were compared and correlated with the other independent variables. RESULTS: Group 1 had 26 eyes, and group 2 had 78 eyes. All TPRK indices were significantly higher for the eyes in group 1 than for those in group 2. The MMC usage was not a significant predictor of the change in ECD (P=0.644), change in CV (P=0.374), and change in the percentage of hexagonality of EC (P=0.164) at W1. However, the use of MMC was a significant predictor of changes in CV (P=0.014) and the change in the percentage of hexagonality of EC (P=0.039) at M3. The duration of laser exposure and the size of the optical zone influenced the correlation of MMC use with the changes in EC indices, postoperatively. CONCLUSION: The use of MMC doesn't affect ECD, CV, and percentage of hexagonality at W1 if other surgical indices are considered. At M3 after operating myopic eyes by TPRK, MMC significantly influence the CV and percentage of hexagonality. The duration of the laser application and the size of the optical zone should be considered when determining the effect of MMC on the EC indices.

Risk factors for corneal endothelial cell loss after phacoemulsification.

PURPOSE: The purpose of this study was to evaluate the changes in corneal endothelial cell density (CECD) occurring after cataract phacoemulsification surgery and identify factors associated with cell loss. MATERIALS AND METHODS: This was a retrospective study involving patients who underwent cataract phacoemulsification surgery between January 1, 2018, and December 31, 2018, at two private hospitals. Demographic data and biometric parameters were obtained preoperatively. Ultrasound metrics were recorded for each operation, including total on time (TOT), total equivalent power in position 3, and cumulative dissipated energy (CDE). Using corneal specular microscopy, CECD was measured preoperatively and postoperatively at 12, 24, and 36 months. Factors associated with decreased CECD were identified. RESULTS: This study included 223 eyes of 133 patients. The mean CECD was 2530.03 ± 285.42 cells/mm2 preoperatively and significantly decreased to 2364.22 ± 386.98 cells/mm2 at 12 months (P < 0.001), 2292.32 ± 319.72 cells/mm2 at 24 months (P < 0.001), and 2242.85 ± 363.65 cells/mm2 at 36 months (P < 0.001). The amount of cell loss was associated with age, gender, preoperative CECD, preoperative anterior chamber depth, lens thickness, TOT, and CDE. Using multivariate analysis, age, preoperative CECD, and TOT were identified as independent predictors for CECD loss 12 months after surgery. CONCLUSION: The greatest decrease in CECD occurred during the first year after cataract surgery, and the amount of cell loss was influenced by both baseline patient characteristics and ultrasound metrics. Longer-term prospective studies in a larger cohort may yield more information.

Endothelial Migration and Regeneration after Penetrating Trauma Injury in a Deep Anterior Lamellar Keratoplasty Graft: Case Presentation and Literature Overview.

Background: Traumatic injuries in eyes previously treated with Deep Anterior Lamellar Keratoplasty (DALK) can lead to ruptures in the Descemet Membrane (DM) and damage to the corneal endothelium, a crucial layer for maintaining corneal clarity. Due to cell cycle constraints, the human corneal endothelium cannot proliferate; instead, it compensates for injury through cell enlargement and migration from adjacent areas. Methods: This study examines a notable case of corneal endothelial cell migration following a penetrating eye injury in a patient previously treated with DALK for keratoconus, supplemented by a review of relevant literature to contextualize the regenerative response. Results: A 39-year-old male with a history of DALK suffered a traumatic eye injury, resulting in damage to the Descemet Membrane and loss of the crystalline lens. After primary repair and considerations for further surgery, the patient's cornea cleared remarkably, with an improved visual acuity. This demonstrates the DM's potential for self-repair through endothelial cell migration. Conclusions: The outcomes suggest that delaying corneal transplant surgery for up to 3 months following Descemet Membrane injury due to ocular trauma could be advantageous. Allowing time for natural healing processes might eliminate the need for further invasive surgeries, thereby improving patient recovery outcomes.

Determination of progressive endothelial cell loss after posterior chamber phakic intraocular lens implantation.

Comments about endothelial cell loss after posterior chamber phakic intraocular lens are provided, with a particular emphasis on the importance of determining progressive postoperative cell density reduction, excluding that related to surgical trauma.

[Outcomes of hemi-Descemet membrane endothelial keratoplasty and phacoemulsification for the treatment of primary Fuchs' endothelial corneal dystrophy combined with cataract]. / Rezul'taty transplantatsii destsemetovoi membrany s endoteliem i fakoemul'sifikatsii pri pervichnoi endotelial'noi distrofii rogovitsy Fuksa, sochetannoi s kataraktoi.

PURPOSE: This study evaluates the long-term results of surgical treatment of patients with Fuchs' endothelial corneal dystrophy and cataract. MATERIAL AND METHODS: The study included 24 patients (24 eyes) with primary Fuchs' endothelial corneal dystrophy and cataract, who underwent cataract phacoemulsification with IOL implantation and of Descemet's membrane endothelial keratoplasty with a semicircular graft (hemi-DMEK). The effect of treatment was assessed by best corrected visual acuity (BCVA), central corneal thickness (CCT) and endothelial cell density (ECD). RESULTS: In total, surgical treatment involved 14 donor corneas that were divided in half during the preparation and isolation of the Descemet's membrane (DM). By month 12 after the surgery an increase in visual functions and graft transparency were observed in 23 patients (23 eyes) out of 24. Repeated keratoplasty was required in one case due to fibrosis of the posterior layers of recipient's corneal stroma. At 12 months postoperatively, the study group showed an increase in BCVA from 0.16±0.1 to 0.75±20, a decrease in CCT from 650.9±4.5 µm to 519.6±43.9, and a decreased in ECD from 2850.5±84.7 cells/mm2 up to 1285.5±277.2 cells/mm2. Thus, the loss of endothelial cells at one year after surgery amounted to 54.9%. CONCLUSIONS: The developed method for transplantation of a semicircular DM fragment provides a tissue-saving approach to endothelial keratoplasty, and considering the high percentage of transparent engraftment of grafts and complete visual rehabilitation, it can be recommended in the treatment of patients with cataract and Fuchs' endothelial corneal dystrophy.

Clinical Evaluation of Corneal Endothelial Parameters following Laser Refractive Surgery in Myopic Eyes: A Review.

Background: The aim of this review was to investigate the influence of various laser refractive surgery methods on the corneal endothelium in myopic patients. The role of the corneal endothelium in laser refractive surgery (LRS) is currently being addressed in the assessment of postoperative corneal edema risk. Methods: Changes in corneal endothelial cell density and morphology after LRS were evaluated based on a systematic review of current studies. The results of a literature search in the PubMed, Science Direct, Google Scholar, and the Web of Science databases, as well as a manual search, were selected for the final review according to the PRISMA 2020 flow diagram. Results: We included 24 prospective clinical trials in the review: surface ablation (twelve), LASIK and FemtoLASIK (two), femtosecond lenticule extraction (two), and comparable studies (eight). Endothelial cell density was determined by specular or in vivo confocal microscopy. In most studies, no statistically significant differences were found between preoperative and postoperative endothelial parameters. In nine studies, the changes were statistically significant, but no vision-threatening complications occurred, and no serious corneal complications developed in any eyes during the follow-up period. Conclusions: Based on collected data, laser keratorefractive surgery appears not to exert a significant effect on the corneal endothelium.

Effect of Intravitreal Aflibercept on Corneal Endothelial Cells.

AIM: To determine the effect of repeated intravitreal injections of aflibercept on the corneal endothelium in patients with diabetic macular edema (DME) and macular edema due to retinal vein occlusion (RVO). METHODS: In a prospective study conducted between January 2021 and November 2023, a total of 87 treatment-naive eyes with DME and RVO were evaluated. The exclusion criteria were surgery or laser intervention during the follow-up period, contact lens wear, cataract surgery in the last 6 months, dystrophy, or other corneal condition that may cause endothelial damage. In addition to routine examinations on the day of application, we also measured the corneal endothelium using specular microscopy on the 1st, 4th and 8th day of injection. We evaluated 4 parameters: endothelial cell density (CD), hexagonality (HEX), coefficient of variability (CV) and central corneal thickness (CCT). First of all, we evaluated the entire cohort of eyes, and then divided it according to 2 criteria; the diagnosis into DME/RVO and according to the lens status into phakic/pseudophakic eyes. RESULTS: A total of 87 eyes of 68 patients were evaluated. The average age of the patients at the time of diagnosis was 66.8 ±9.3 years. Within the cohort 51 (59%) eyes were phakic and 36 (41%) pseudophakic. A total of 61 (70%) eyes with a diagnosis of DME were treated, and 26 (30%) with RVO. During the follow-up, there were no significant changes in the average values of CD, HEX, CV, CCT due to aflibercept treatment, either in the whole group or in subgroups according to diagnosis or lens condition. CONCLUSIONS: The results of this study suggest that intravitreal administration of aflibercept in patients with DME and RVO did not have an impact on corneal endothelial parameters, including CCT, HEX, CD and CV. These parameters were measured using endothelial microscopy during an 8-injection observation period.

Comparison between Early Clinical Results of Dual-Linear and Conventional Foot-Pedal Control in Phacoemulsification.

BACKGROUND: The aim of this study was to compare early clinical results regarding the safety and efficacy of dual-linear vs. conventional foot-pedal control in cataract surgery. METHODS: This was a paired-eye contralateral, retrospective, observational study. Each patient underwent cataract surgery in both eyes: one eye with dual-linear foot-pedal control (study group) and the other eye with conventional foot-pedal control (control group). Absolute phaco time (APT), average phaco power, effective phaco time (EPT), and surgical complications were analyzed and compared. Corneal endothelial cell count, corneal thickness, corneal volume, and best-corrected distance visual acuity (BCDVA) were measured preoperatively and at 1 week, 1 month, and 3 months postoperatively. RESULTS: A total of 94 patients (188 eyes) were enrolled. The respective APT, average phaco power, and EPT values were 7.05 ± 5.31 s, 28.4 ± 1.00, and 2.05 ± 1.56 s in the study group and 6.82 ± 6.48 s, 18.9 ± 1.74, and 1.35 ± 1.35 s in the control group. CONCLUSIONS: The average phaco power and EPT values were significantly higher in the study group. The safety of the dual-linear foot pedal was comparable to that of a conventional pedal in terms of endothelial cell loss, central corneal thickness, and surgical complications.

Do intravitreal anti-VEGF injections have an effect on corneal endothelial remodeling in children with premature retinopathy?

PURPOSE: This study was carried out to investigate the effects of retinopathy of prematurity (ROP) and intravitreal antivascular endothelial growth factor (VEGF) injections on the corneal endothelium in the childhood period of patients who have had ROP. METHODS: The material of comparative case-control clinical study consisted of patients followed up with ROP between February 2013 and February 2023. The eyes in the study group were divided into two subgroups consisting of those who received intravitreal anti-VEGF injections (subgroup 1) and those who were followed up only (subgroup 2). Central corneal endothelial cell density (ECD), coefficient of variation (CV), central corneal thickness (CCT), and pleomorphism parameters in the childhood period were evaluated by corneal specular microscopy and compared with age-matched healthy control subjects. RESULTS: There were 84 eyes of 42 patients with ROP in the study group and 80 eyes of 40 healthy children in the control group. Mean CCT was significantly higher in subgroup 1 and the control group than in subgroup 2 (p = 0.037), and mean ECD was significantly higher in subgroup 2 than in subgroup 1 and the control group (p < 0.001). There was no significant difference between subgroup 1 and the control group in mean ECD and CCT values (p = 1.000 for both cases). CONCLUSIONS: Considering that ROP patients who received intravitreal anti-VEGF injections had more advanced-stage ROP than ROP patients who were followed up only, these findings suggest that intravitreal anti-VEGF applications in ROP cases may lead to corneal endothelial parameters similar to those of healthy eyes.

Targeting the NRF2 pathway: A promising approach for corneal endothelial dysfunction.

Maintaining corneal endothelial function is required for vision, and corneal endothelial dysfunction is a major cause of visual deficits and blindness worldwide. To date there has been a dearth of innovation for therapeutics targeting the corneal endothelium. However, recent advances in understanding the role of oxidative stress and mitochondrial dysfunction have revealed potential avenues for the development of new therapies. This review summarizes recent developments in elucidating the role of the NRF2 pathway in corneal endothelial health and disease, focusing specifically on Fuchs' endothelial corneal dystrophy and the loss of corneal endothelial cells associated with cataract surgery. The pro-mitochondrial and antioxidant phenotype elicited by NRF2 activation offers a promising opportunity for new therapeutics for the diseased corneal endothelium.

The role of corneal endothelium in macular corneal dystrophy development and recurrence.

Macular corneal dystrophy (MCD) is a progressive, bilateral stromal dystrophic disease that arises from mutations in carbohydrate sulfotransferase 6 (CHST6). Corneal transplantation is the ultimate therapeutic solution for MCD patients. Unfortunately, postoperative recurrence remains a significant challenge. We conducted a retrospective review of a clinical cohort comprising 102 MCD patients with 124 eyes that underwent either penetrating keratoplasty (PKP) or deep anterior lamellar keratoplasty (DALK). Our results revealed that the recurrence rate was nearly three times higher in the DALK group (39.13%, 9/23 eyes) compared with the PKP group (10.89%, 11/101 eyes), suggesting that surgical replacement of the corneal endothelium for treating MCD is advisable to prevent postoperative recurrence. Our experimental data confirmed the robust mRNA and protein expression of CHST6 in human corneal endothelium and the rodent homolog CHST5 in mouse endothelium. Selective knockdown of wild-type Chst5 in mouse corneal endothelium (ACsiChst5), but not in the corneal stroma, induced experimental MCD with similar extracellular matrix synthesis impairments and corneal thinning as observed in MCD patients. Mice carrying Chst5 point mutation also recapitulated clinical phenotypes of MCD, along with corneal endothelial abnormalities. Intracameral injection of wild-type Chst5 rescued the corneal impairments in ACsiChst5 mice and retarded the disease progression in Chst5 mutant mice. Overall, our study provides new mechanistic insights and therapeutic approaches for MCD treatment by high-lighting the role of corneal endothelium in MCD development.

Ovol2 promoter mutations in mice and human illuminate species-specific phenotypic divergence.

Pathogenic variants in the highly conserved OVOL2 promoter region cause posterior polymorphous corneal dystrophy (PPCD) 1 by inducing an ectopic expression of the endothelial OVOL2 mRNA. Here we produced an allelic series of Ovol2 promoter mutations in the mouse model including the heterozygous c.-307T>C variant (RefSeq NM_021220.4) causing PPCD1 in humans. Despite the high evolutionary conservation of the Ovol2 promoter, only some alterations of its sequence had phenotypic consequences in mice. Four independent sequence variants in the distal part of the Ovol2 promoter had no significant effect on endothelial Ovol2 mRNA level or caused any ocular phenotype. In contrast, the mutation c.-307T>C resulted in increased Ovol2 expression in the corneal endothelium. However, only a small fraction of adult mice c.-307T>C heterozygotes developed ocular phenotypes such as irido-corneal adhesions, and corneal opacity. Interestingly, phenotypic penetrance was increased at embryonic stages. Notably, c.-307T>C mutation is located next to the Ovol1/Ovol2 transcription factor binding site. Mice carrying an allele with a deletion encompassing the Ovol2 binding site c.-307_-320del showed significant Ovol2 gene upregulation in the cornea endothelium and exhibited phenotypes similar to the c.-307T>C mutation. In conclusion, although the mutations c.-307T>C and -307_-320del lead to a comparably strong increase in endothelial Ovol2 expression as seen in PPCD1 patients, endothelial dystrophy was not observed in the mouse model, implicating species-specific differences in endothelial cell biology. Nonetheless, the emergence of dominant ocular phenotypes associated with Ovol2 promoter variants in mice implies a potential role of this gene in eye development and disease.

COVID-19 related changes in corneal curvature and endothelium after mild infection.

PURPOSE: To investigate subclinical corneal changes using corneal topography in the evaluation of corneal curvature and specular microscopy in the evaluation of the endothelial layer after mild coronavirus disease 2019 (COVID-19). METHODS: In this prospective study, 112 eyes of 56 individuals with mild COVID-19 who recovered were investigated. Mean cell density (CD), mean coefficient of variation (CV), mean percentage of hexagonal cells, mean cell area (AVG), and central corneal thickness (CCT) were recorded from specular microscopy. K readings, including simulated keratometry flat (K1), simulated keratometry steep (K2), average keratometry (Kmean) and maximum keratometry (Kmax), pachymetric measurement and central corneal thickness (CCT), corneal volume (CV), topographic astigmatism (TA), curvature asymmetry front (CAf) and curvature asymmetry back (CAb) were recorded from corneal topography. Best corrected visual acuity (BCVA), spherical equivalant and biometric measurements were recorded. RESULTS: The mean time interval between examinations before and after COVID-19 infection was approximately one year. Analysis of specular microscopy data showed a statistically significant change in all endothelial cell parameters (p<0.001) except the cell count (p = 0.358). The median (range) endothelial cell density (ECD) value was significantly lower after COVID-19 at 2356 (2289-2400) than before, when it was 2596 (2545-2640). Furthermore, CCT values showed a significant increase (p<0.001). The topographic values including K2, Kmax and TA and biometric measurements did not change. The Spherical Equivalant (SE) values showed significant myopic progression after COVID-19 (p<0.001). CONCLUSION: Endothelial parameters changed more than the changes in corneal curvature and ocular biometric measurements after mild COVID-19. The decrease in endothelial cell number and hexagonality and increase in polymorphism after COVID-19 were striking.

Aqueous Humor Circulation in the Era of Minimally Invasive Surgery for Glaucoma.

Glaucoma surgery with implantation of aqueous humor draining microstents may compromise long-term corneal health by disrupting aqueous humor circulation. The effect of stent numbers on this circulation was interrogated to determine the number of stents associated with minimal circulation disruption. An in vitro anterior eye model perfusion system was constructed with multiple exit ports. A 3-D model of the anterior eye was imported into ABAQUS CFD, analyzes were carried out for unsteady laminar flow and solved using Navier-Stokes equations. DT Vision Foundry was used to analyze velocity contour plot images. The field variable results output for the CFD model were fluid wall shear, fluid pressure and fluid velocity. In vitro, "aqueous" fluid flow is high through a single stent and "aqueous" stagnation is greatest in the quadrants 180° away. Increasing stent port numbers, results in an exponential decrease in the stagnant flow locations. High wall shear stress was seen in the single stent model and is markedly reduced after a second and subsequent stents are introduced. We identify two factors potentially contributing to corneal compromise post glaucoma drainage surgery: aqueous humor stagnation, remote to the stent site and higher exit flows imparting increased stent exit shear stress (particularly with a single stent). With 4 stents, there is minimal disruption of anterior chamber circulation (mimicking physiological conditions). Furthermore we propose that aqueous humor circulation disruption via the usual single-exit port approach disrupts aqueous humor circulation with long-term consequences for corneal health.