Regional variability in corneal endothelial cell density between guttae and non-guttae areas in Fuchs endothelial corneal dystrophy

Assessing Fuchs Corneal Endothelial Dystrophy Using Artificial Intelligence-Derived Morphometric Parameters From Specular Microscopy Images

PURPOSE

The aim of this study was to evaluate the efficacy of artificial intelligence-derived morphometric parameters in characterizing Fuchs corneal endothelial dystrophy (FECD) from specular microscopy images.

METHODS

This cross-sectional study recruited patients diagnosed with FECD, who underwent ophthalmologic evaluations, including slit-lamp examinations and corneal endothelial assessments using specular microscopy. The modified Krachmer grading scale was used for clinical FECD classification. The images were processed using a convolutional neural network for segmentation and morphometric parameter estimation, including effective endothelial cell density, guttae area ratio, coefficient of variation of size, and hexagonality. A mixed-effects model was used to assess relationships between the FECD clinical classification and measured parameters.

RESULTS

Of 52 patients (104 eyes) recruited, 76 eyes were analyzed because of the exclusion of 26 eyes for poor quality retroillumination photographs. The study revealed significant discrepancies between artificial intelligence-based and built-in microscope software cell density measurements (1322 ± 489 cells/mm 2 vs. 2216 ± 509 cells/mm 2 , P < 0.001). In the central region, guttae area ratio showed the strongest correlation with modified Krachmer grades (0.60, P < 0.001). In peripheral areas, only guttae area ratio in the inferior region exhibited a marginally significant positive correlation (0.29, P < 0.05).

CONCLUSIONS

This study confirms the utility of CNNs for precise FECD evaluation through specular microscopy. Guttae area ratio emerges as a compelling morphometric parameter aligning closely with modified Krachmer clinical grading. These findings set the stage for future large-scale studies, with potential applications in the assessment of irreversible corneal edema risk after phacoemulsification in FECD patients, as well as in monitoring novel FECD therapies.

Comparison of automated corneal endothelial cell analysis in healthy and postoperative eyes with phakic intraocular lens: a cross-sectional study and literature review

PURPOSE

Measurement of corneal endothelial cells is critical for postoperative evaluation of phakic intraocular lens (pIOL) surgery. However, inter-instrument differences in corneal endothelial cell density (ECD) after pIOL implantation have not yet been reported. This study aimed to compare automated corneal endothelial cell analysis between CellChek-20 (Konan Medical, Hyogo, Japan) and EM-4000 (Tomey, Nagoya, Japan) in healthy and postoperative eyes with pIOL.

METHODS

We retrospectively analyzed 154 healthy and 236 postoperative eyes after pIOL surgery. Endothelial cell measurements were performed using CellChek-20 and EM-4000 with autofocusing and automated image analysis. ECD, percentage of hexagonal cells (HEX), coefficient of variation in cell size (CoV), and central corneal thickness (CCT) were compared between the two devices.

RESULTS

The ECDs of the two devices were highly correlated in both healthy (Spearman's correlation coefficient [r] = 0.805; p < 0.001) and postoperative (r = 0.901; p < 0.001) groups. ECD from CellChek-20 was higher than EM-4000 in both healthy (mean difference = 228.9 cells/mm2; p < 0.001) and postoperative (mean difference = 115.6 cells/mm2; p < 0.001) groups. The CCT values also showed a strong correlation in healthy eyes (r = 0.974; p < 0.001) and in postoperative eyes (r = 0.936; p < 0.001); however, significant inter-instrument differences were observed. HEX and CV showed significant differences and relatively weak correlations (r < 0.7) between the two devices in both healthy and postoperative groups.

CONCLUSION

The ECD values between the two instruments were correlated, but that of the CellChek-20 was significantly higher than that of the EM-4000 in both healthy and postoperative eyes after pIOL surgery. Most previous studies have also shown that the Konan software overestimated the ECD compared to other products in automatic measurement mode. The possibility of measurement bias should be considered when replacing equipment used for corneal endothelial cell measurements.

Exploring single-cell RNA sequencing as a decision-making tool in the clinical management of Fuchs' endothelial corneal dystrophy

Single-cell RNA sequencing (scRNA-seq) has enabled the identification of novel gene signatures and cell heterogeneity in numerous tissues and diseases. Here we review the use of this technology for Fuchs' Endothelial Corneal Dystrophy (FECD). FECD is the most common indication for corneal endothelial transplantation worldwide. FECD is challenging to manage because it is genetically heterogenous, can be autosomal dominant or sporadic, and progress at different rates. Single-cell RNA sequencing has enabled the discovery of several FECD subtypes, each with associated gene signatures, and cell heterogeneity. Current FECD treatments are mainly surgical, with various Rho kinase (ROCK) inhibitors used to promote endothelial cell metabolism and proliferation following surgery. A range of emerging therapies for FECD including cell therapies, gene therapies, tissue engineered scaffolds, and pharmaceuticals are in preclinical and clinical trials. Unlike conventional disease management methods based on clinical presentations and family history, targeting FECD using scRNA-seq based precision-medicine has the potential to pinpoint the disease subtypes, mechanisms, stages, severities, and help clinicians in making the best decision for surgeries and the applications of therapeutics. In this review, we first discuss the feasibility and potential of using scRNA-seq in clinical diagnostics for FECD, highlight advances from the latest clinical treatments and emerging therapies for FECD, integrate scRNA-seq results and clinical notes from our FECD patients and discuss the potential of applying alternative therapies to manage these cases clinically.

Applications of Imaging Technologies in Fuchs Endothelial Corneal Dystrophy: A Narrative Literature Review

Fuchs endothelial corneal dystrophy (FECD) is a complex genetic disorder characterized by the slow and progressive degeneration of corneal endothelial cells. Thus, it may result in corneal endothelial decompensation and irreversible corneal edema. Moreover, FECD is associated with alterations in all corneal layers, such as thickening of the Descemet membrane, stromal scarring, subepithelial fibrosis, and the formation of epithelial bullae. Hence, anterior segment imaging devices that enable precise measurement of functional and anatomical changes in the cornea are essential for the management of FECD. In this review, the authors will introduce studies on the application of various imaging modalities, such as anterior segment optical coherence tomography, Scheimpflug corneal tomography, specular microscopy, in vitro confocal microscopy, and retroillumination photography, in the diagnosis and monitoring of FECD and discuss the results of these studies. The application of novel technologies, including image processing technology and artificial intelligence, that are expected to further enhance the accuracy, precision, and speed of the imaging technologies will also be discussed.

Corneal Guttae After Descemet Membrane Endothelial Keratoplasty

PURPOSE

The aim of this study was to report on the occurrence of corneal guttae after Descemet membrane endothelial keratoplasty (DMEK).

METHODS

In this retrospective case series, 13 eyes of 13 patients who underwent DMEK at 2 tertiary referral centers between 2007 and 2021 (average available follow-up 73 ± 52 months, range 18-174 months) and showed corneal guttae during postoperative examinations were included. Eye bank images were retrospectively reviewed.

RESULTS

Occurrence of guttae was observed by specular microscopy in 13 eyes. In 11 cases, presence of guttae was confirmed by confocal microscopy and in 1 case by histology. Five eyes showed an increase in guttae density during the postoperative course. Surgery indications were Fuchs endothelial corneal dystrophy (n = 11), pseudophakic bullous keratopathy (n = 1), and DMEK graft failure after allograft rejection (n = 1); the latter eye had shown no signs of guttae after primary DMEK. Two eyes with guttae required a repeat DMEK due to graft failure. At the last available follow-up, all 11 remaining eyes had clear corneas and 10 eyes had a best-corrected visual acuity of ≥0.9 (decimal). During donor cornea processing in the eye bank, no guttae were observed on the donor tissue.

CONCLUSIONS

Corneal guttae can occur after DMEK including in eyes operated for indications other than Fuchs endothelial corneal dystrophy and most likely guttae were present on the donor graft but were not detectable by routine slit-lamp and light microscopy evaluation in the eye bank. Postoperative guttae density varies among patients and especially small isolated guttae do not seem to affect clinical outcomes.

Experimental Oxidative Stress Breaks Down the Barrier Function of the Corneal Endothelium

Purpose: The fluid pump and barrier functions of the corneal endothelium maintain stromal deturgescence required for corneal transparency. The effect of oxidative stress, a hallmark of Fuchs endothelial corneal dystrophy (FECD), on the endothelial barrier function has been investigated. Methods: The endothelium of porcine corneas ex vivo was exposed to (1) membrane permeable oxidants (H₂O₂, 100 μM, 1 h; tert-butyl-hydroperoxide, 100 μM, 1 h), or (2) ultraviolet A (UVA) with photosensitizers for 15 min, riboflavin (50 μM) or tryptophan (Trp) (100 μM). The effects on the apical junction complex were analyzed by (1) immunostaining the perijunctional actomyosin ring (PAMR) and ZO-1 and (2) assessment of paracellular flux of fluorescein isothiocyanate (FITC)-avidin across cultured endothelial cells grown on biotinylated-gelatin film. The extent of oxidative stress was quantified by changes in intracellular reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) in addition to lipid peroxidation and release of lactate dehydrogenase (LDH). Results: Both methods of oxidative stress led to the disruption of PAMR and ZO-1 concurrent with changes in ROS levels, depolarization of MMP, increased lipid peroxidation, elevated LDH release, and increased permeability of FITC-avidin. The effects of direct oxidants were opposed by SB-203580 [p38 mitogen-activating protein (MAP) kinase inhibitor; 10 μM]. The damage by UVA+photosensitizers was blocked by extracellular catalase (10,000 U/mL). Conclusions: (1) Acute oxidative stress breaks down the barrier function through destruction of PAMR in a p38 MAP kinase-dependent manner. (2) UVA+photosensitizers elicit the breakdown of PAMR via type I reactions, involving H₂O₂ release. (3) Blocking the oxidative stress prevents loss of barrier function, which could be helpful in the therapeutics of FECD.

[Outcomes of cataract surgery in patients with Fuchs endothelial corneal dystrophy]

PURPOSE

While endothelial keratoplasty has become the standard treatment for Fuchs dystrophy, the strategy for first-line surgery in patients with associated cataract is still debated. The purpose of this study was to evaluate the surgical outcomes of eyes with Fuchs endothelial corneal dystrophy (FECD) undergoing phacoemulsification alone, to ascertain preoperative factors that predict the need for endothelial keratoplasty (EK).

METHODS

Single-center retrospective study. Cataract surgery alone was performed in 64 eyes of 50 patients with FECD. This decision was made if the patient did not have morning blur, the central corneal thickness (CCT) was below 630 microns, and endothelial cells were visible in the periphery.

RESULTS

Mean follow-up was 21 months (range 5-55 months). The mean preoperative CCT was 571±43μm. 6 months after surgery, it was 584±52μm (P=0.12). During follow-up, 14 eyes (22%) required an EK because of poor visual outcome after cataract surgery alone. Mean pre-operative CCT of these eyes (595±23μm) was significantly higher than eyes that did not require EK during follow-up (564±45μm, P=0.022). Over 570 microns, 34% of eyes required an endothelial keratoplasty after the cataract surgery alone.

CONCLUSIONS

CCT below 630μm associated with the absence of morning blur are preoperative criteria allowing 78.1% eyes with FECD to obtain good visual outcomes after cataract surgery alone. In these eyes, EK can therefore be avoided while ensuring good results.

Fuchs endothelial corneal dystrophy: The vicious cycle of Fuchs pathogenesis

Fuchs endothelial corneal dystrophy (FECD) is the most common primary corneal endothelial dystrophy and the leading indication for corneal transplantation worldwide. FECD is characterized by the progressive decline of corneal endothelial cells (CECs) and the formation of extracellular matrix (ECM) excrescences in Descemet's membrane (DM), called guttae, that lead to corneal edema and loss of vision. FECD typically manifests in the fifth decades of life and has a greater incidence in women. FECD is a complex and heterogeneous genetic disease where interaction between genetic and environmental factors results in cellular apoptosis and aberrant ECM deposition. In this review, we will discuss a complex interplay of genetic, epigenetic, and exogenous factors in inciting oxidative stress, auto(mito)phagy, unfolded protein response, and mitochondrial dysfunction during CEC degeneration. Specifically, we explore the factors that influence cellular fate to undergo apoptosis, senescence, and endothelial-to-mesenchymal transition. These findings will highlight the importance of abnormal CEC-DM interactions in triggering the vicious cycle of FECD pathogenesis. We will also review clinical characteristics, diagnostic tools, and current medical and surgical management options for FECD patients. These new paradigms in FECD pathogenesis present an opportunity to develop novel therapeutics for the treatment of FECD.