IC3D classification of corneal dystrophies--edition 2

A Novel Symptomatic Lecithin-Cholesterol Acyltransferase Gene Mutation With Corneal Amyloidosis

PURPOSE

To present ocular clinical, histological, systemic, and genetic findings of a patient with familial lecithin-cholesterol acyltransferase (LCAT) deficiency caused by a novel genetic variant of the LCAT gene associated with secondary corneal amyloidosis.

METHODS

Case report.

RESULTS

A 74-year-old woman presented with decreased visual acuity (VA), sensitivity to light, and progressive whitening of both corneas for approximately 20 years. The patient had undergone penetrating keratoplasty (PKP) on the right eye 6 years ago. Ophthalmologic examination revealed decreased VA in both eyes (OD: 0.05, OS: 0.3), and even further reduced glare VA (OD: 0.05, OS: 0.1), diffuse whitish corneal opacity involving the total thickness of the corneal stroma without crystalline deposits, and a marked peripheral diffuse arcus. Systemic examination revealed severely reduced plasma high-density lipoprotein cholesterol levels, target cells in blood smear, and chronic normochromic anemia. Clinically, LCAT deficiency was the most likely diagnosis. Further genetic analysis confirmed the diagnosis. The patient is homozygous for the novel variant c.943T>C (p.Trp315Arg) in the LCAT gene. Histologic examination of the cornea removed during the first keratoplasty revealed amyloid deposits. The cornea removed at the second keratoplasty had small vacuoles in the anterior stroma, indicating recurrence of lipid deposition.

CONCLUSIONS

LCAT deficiency is a rare genetic disorder that can cause corneal opacities because of lipid deposition in the cornea. Systemic manifestations may help in the differential diagnosis to other diseases associated with severe high-density lipoprotein cholesterol reduction. Genetic analysis is employed to confirm the diagnosis. Some mutations in the LCAT gene seem to be associated with secondary corneal amyloidosis. Further investigation of this association is warranted. A recurrence of corneal opacity after PKP seems to occur mainly in the anterior corneal stroma.

Recurrence Characteristics on Optical Coherence Tomography and Treatments of Reis-Bücklers Corneal Dystrophy After Phototherapeutic Keratectomy or Penetrating Keratoplasty

PURPOSE

To evaluate the recurrence characteristics on optical coherence tomography and clinical outcomes after phototherapeutic keratectomy (PTK) or penetrating keratoplasty (PKP) in patients with Reis-Bücklers corneal dystrophy (RBCD).

DESIGN

Retrospective interventional case series.

METHODS

Seventeen patients with RBCD (31 eyes, including 6 surgery-naïve eyes and 25 surgical eyes) received 44 surgical interventions from 1996 through 2022. PTK or PKP was performed as the initial surgical procedure. Significant recurrence was determined when best spectacle-corrected visual acuity decreased at least 2 lines with increased opacity in the superficial cornea. Repeated PTK or PTK on the corneal graft (CG-PTK) was considered if patients could not endure poor vision due to significant recurrence. Recurrence depth and annual increase in thickness of the central cornea and subepithelial deposits were assessed by anterior segment optical coherence tomography.

RESULTS

The mean follow-up time was 12.8 ± 8.5 years (range, 2.0-25.5 years). The mean logMAR best spectacle-corrected visual acuity improved from 1.24 ± 0.48 preoperatively to 0.27 ± 0.09 postoperatively in the initial PTK group (13 eyes, P < .001), from 1.84 ± 0.69 to 0.40 ± 0.13 in the PKP group (12 eyes, P < .001), from 1.04 ± 0.46 to 0.30 ± 0.07 in the repeated PTK group (12 times in 7 eyes, P < .001), and from 1.29 ± 0.43 to 0.39 ± 0.11 in the CG-PTK group (7 times in 5 eyes, P = .001). The median significant recurrence time was 27 months (95% confidence interval 23.9-30.1), 96 months (84.1-107.9), 31 months (28.8-33.1), and 24 months (19.8-28.2), respectively (P < .001). The depth of superficial deposits located between the epithelium and the anterior stroma was approximately 115 µm (85-159 µm). The annual thickening of subepithelial deposits was 14 ± 2 µm after initial PTK, 7 ± 3 µm after PKP, 14 ± 3 µm after repeated PTK, and 30 ± 11 µm after CG-PTK, compared to 4 ± 2 µm in surgery-naïve eyes (P = .002, .515, .002, <.001). The thickness of the central cornea increased by 15 ± 2 µm, 7 ± 2 µm, 15 ± 3 µm, and 31 ± 10 µm per year in the 4 surgery groups, respectively, compared to 5 ± 2 µm in surgery-naïve eyes (P = .001, .469, .001, <.001).

CONCLUSIONS

Better visual acuity can be achieved after PTK than PKP for treatment of RBCD. The annual thickening of subepithelial deposits may approximate an increase in central corneal thickness. The superficial distribution of subepithelial deposits makes it feasible to perform repeated PTK, even on the corneal allograft, for recurrent RBCD.

[Pathogenesis of Fuchs endothelial corneal dystrophy, the fibrillar layer and individualized treatment]

Fuchs endothelial corneal dystrophy (FECD) is a genetic and age-associated corneal disease characterized by an accelerated loss of corneal endothelial cells and an increased subendothelial deposition of extracellular matrix (ECM). Clinically, advanced disease leads to corneal edema with subsequent reduction in visual acuity. In the majority of patients with advanced FECD, a fibrillar layer (FL) appears on the posterior corneal surface. This FL is mostly localized in the inferotemporal corneal quadrant, marks areas with significantly reduced endothelial cell density and increased corneal thickness in the sense of edema and can be visualized and measured using Scheimpflug backscatter analysis due to increased backscatter. FECD is currently the most common indication for corneal transplantation worldwide, usually in the form of Descemet membrane endothelial keratoplasty (DMEK). New treatment approaches include variations of DMEK surgery such as hemi- or quarter DMEK with individualized and smaller grafts or Descemet membrane stripping only (DSO). In the future, clinical imaging of the FL as a particularly affected endothelial area could be important for FECD progression assessment and planning of surgical interventions. This article provides an overview of the current state of research on the clinical aspects, pathogenesis, fibrillar layer and individualized treatment of FECD.

Corneal Epithelial Wavefront Error as a Novel Diagnostic Marker for Epithelial Basement Membrane Dystrophy

Synopsis: Corneal epithelial wavefront error and epithelial thickness variance qualify as highly sensitive and specific biomarkers for epithelial basement membrane dystrophy (EBMD). The biomarkers show a normalization after treatment of EBMD with phototherapeutic keratectomy. Purpose: To gauge the diagnostic value of epithelial basement membrane dystrophy (EBMD), a novel spectral-domain optical coherence tomography (SD-OCT)-based imaging modality for simultaneous morphological (thickness profile) and refractive (optical wavefront) assessment of the corneal epithelial layer in one of the most common but often underdiagnosed corneal dystrophies. Methods: In this prospective observational study, a total of 32 eyes of 32 patients diagnosed with EBMD and 32 eyes of 32 healthy control subjects were examined with high-resolution anterior segment SD-OCT (MS-39; CSO, Florence, Italy). Various epithelial thickness and epithelial wavefront-derived terms were compared between groups and receiver operating characteristic (ROC) curves were computed to analyze the diagnostic capacity of the respective parameters. A total of 17 of 32 EBMD patients underwent treatment with phototherapeutic keratectomy (PTK) and were followed up for 3 months. Results: Epithelial thickness variance (60.4 ± 56.7 µm versus 7.6 ± 6.1 µm) and interquartile range (11.0 ± 6.9 versus 3.3 ± 1.9 µm) were markedly elevated in EBMD patients as compared with healthy controls (both with p < 0.001). Epithelial wavefront analysis showed a highly statistically significant excess in all examined aberration terms in EBMD patients (all with p < 0.001). Significantly greater areas under the curve (AUCs) were yielded by the epithelial wavefront-derived parameters (e.g., total epithelial wavefront error: AUC = 0.966; 95% confidence interval (CI) 0.932-1) than by the epithelial thickness-derived parameters (e.g., variance: AUC = 0.919; 95% CI 0.848-0.990). Conclusions: Corneal epithelial wavefront aberrometry proved valuable as an objective biomarker for EBMD, with high sensitivity and specificity. PTK resulted in a reduction of morphological and refractive epithelial irregularities in EBMD.

Petal-shaped corneal pattern in a patient with posterior amorphous corneal dystrophy

Purpose

To describe the petal-shaped corneal pattern in a patient with posterior amorphous corneal dystrophy.

Observation

A 19-year-old male affected by Graves' disease presented corneal grey sheet-like opacities and high hyperopia. Corneal topography showed reduced k-values compatible with cornea plana and reduced corneal pachymetry. The anterior segment optical coherence tomography showed a hyperreflective band at the posterior stroma-Descemet-Endothelium layers in both eyes. Slit lamp examination with cobalt blue filter showed a corneal pattern resembling a petal in right eye; the pattern was similar but incomplete in left eye.

Conclusion & importance

After an exhaustive literature review conducted from October 1st to 30th, 2023, utilizing online databases like PubMed and Google Scholar, and employing keywords such as "Corneal Dystrophy," "Slit Lamp," "Cornea," and "Posterior Amorphous Corneal Dystrophy," we found no previous reports detailing the whole corneal pattern using a blue cobalt filter on the slit lamp in cases of posterior amorphous corneal dystrophy. Cobalt blue filter was an effective method for capturing the full photographic corneal pattern of the patient posterior amorphous corneal dystrophy.

[The latest IC3D classification of corneal dystrophies-Overview and changes of the 3rd edition]

The International Committee on Classification of Corneal Dystrophies (IC3D) was founded in 2005 to address difficulties arising from the outdated nomenclature for corneal dystrophies (CD) and to correct misconceptions in the literature. For each of the 22 CDs, a separate template was created to represent the current clinical, pathological and genetic knowledge of the disease. In addition, each template contains representative clinical photographs as well as light and electron microscopic images and, if available, confocal microscopic and coherence tomographic images of the respective CD. After the first edition was published in 2008, the revised version followed in 2015. The third edition of the IC3D was published as open access in February 2024. The latest edition is intended to serve as a reference work in everyday clinical practice and facilitate the diagnosis of CD, which might sometimes be difficult. This article provides an overview of the diagnostic and treatment principles of CD and presents the IC3D and its changes over time.

Descemet Membrane Endothelial Keratoplasty (DMEK) for Severe Verrucous Posterior Polymorphous Corneal Dystrophy with Uncommon Clinical and Ultrastructural Findings

PURPOSE

To report a case of severe verrucous posterior polymorphous corneal dystrophy (PPCD) and cataract, which was treated with Descemet membrane endothelial keratoplasty (DMEK) and simultaneous cataract surgery as a triple procedure (Triple-DMEK).

METHODS

A 62-year-old female patient presented to our department for co-evaluation of advanced PPCD with cataract and progressive light sensitivity in both eyes. The clinical examination demonstrated unusual clinical findings with prominent verrucous lesions on the posterior surface of the cornea without corneal decompensation. We performed a Triple-DMEK in case of simultaneous cataract. The corneal tissue was examined by light and transmission electron microscopy.

RESULTS

Intraoperatively, it was difficult to remove the verrucous structures completely after classical descemetorhexis. Light microscopic examination demonstrated epithelium-like transformation of the corneal endothelium by immunostaining (cytokeratin AE1/3 staining). Transmission electron microscopy revealed thickening of Descemet's membrane (18.5 to 30.0 µm). The anterior banded layer had a normal structure and was slightly thickened (3.5 to 5.5 µm). A normal posterior non-banded layer (PNBL) was observed but thinned (2.5 to 4.0 µm) or missing. It was followed by an altered PNBL with abnormal fibrillary inclusions, which was strongly and variably thickened (11.0 to 24.5 µm). The corneal endothelium was degenerated, partially absent, and epithelial-like altered. The nodular lesions were found to consist of a few degenerated cells that were embedded in an amorphous extracellular matrix interspersed with collagen fibers, which were not arranged in regular lamellae, forming the corneal stroma. The occurrence of pigment granules among the cellular debris suggested that the cells were endothelial cells. The corrected distance visual acuity improved from 20/50 to 20/30 in the right eye (+ 0.00/- 1.75/157°) and from 20/60 to 20/30 in the left eye (+ 0.00/- 1.75/33°), with significant improvement in light sensitivity.

CONCLUSION

The clinical and ultrastructural findings seem to be an unusual variant of the typical characteristic appearance of a PPCD. This case demonstrates that Triple-DMEK is feasible even in very advanced dystrophic changes of the posterior corneal surface, with good morphological and functional results.

Evolution of therapeutic strategy based on oxidant-antioxidant balance for fuchs endothelial corneal dystrophy

Fuchs endothelial corneal dystrophy (FECD) stands as the most prevalent primary corneal endothelial dystrophy worldwide, posing a significant risk to corneal homeostasis and clarity. Corneal endothelial cells exhibit susceptibility to oxidative stress, suggesting a nuanced relationship between oxidant-antioxidant imbalance and FECD pathogenesis, irrespective of FECD genotype. Given the constrained availability of corneal transplants, exploration into non-surgical interventions becomes crucial. This encompasses traditional antioxidants, small molecule compounds, biologics, and diverse non-drug therapies, such as gene-related therapy, hydrogen therapy and near infrared light therapy. This review concentrates on elucidating the mechanisms behind oxidant-antioxidant imbalance and the evolution of strategies to restore oxidant-antioxidant balance in FECD. It provides a comprehensive overview of both conventional and emerging therapeutic approaches, offering valuable insights for the advancement of non-surgical treatment modalities. The findings herein might establish a robust foundation for future research and the therapeutic strategy of FECD.

Repeat Femtosecond-Assisted Anterior Lamellar Keratoplasty for Recurrence of TGF B I Dystrophy in Eyes After Previous FALK

PURPOSE

To report the management of recurrent TGF BI dystrophy after prior femtosecond-assisted anterior lamellar keratoplasty (FALK) with repeat FALK.

METHODS

Clinical and histopathological study of 2 eyes of 2 patients with a recurrence of TGFBI dystrophy. Patient 1 had Reis-Buckler corneal dystrophy, and patient 2 had granular corneal dystrophy GCD type 1.

RESULTS

Patient 1 had FALK 8 years ago, when she was 23 years old. Patient 2 had FALK 7 years ago at the age of 24 years. Slit-lamp examination showed recurrence in the subepithelial layer of the anterior lamellar graft as confluent chalky white granular deposits. Anterior segment optical coherence tomography highlighted the deposits in the subepithelial region of the anterior lamellar graft. The anterior lamellar graft with deposits was removed and replaced with another graft created using femtolaser dissection of a healthy donor. The parameters for femtosecond laser-assisted donor dissection was similar to the size and depth as the previously used donor. The best-corrected visual acuity was restored to 20/30 in patient 1 and 20/25 in patient 2. The histology of the anterior lamellar graft showed eosinophilic deposits between the epithelium and the Bowman layer in both samples. In addition, the corneal sample from patient 2 revealed Bowman layer breach at some places and few deposits at 1 edge of the lamellar graft.

CONCLUSIONS

Repeat FALK with a healthy donor is effective in the management of recurrence of deposits. The histology of the recurrence in the anterior lamellar graft revealed eosinophilic deposits predominantly between the epithelium and Bowman layer.

Classic lattice corneal dystrophy: a brief review and summary of treatment modalities

PURPOSE

To provide a brief summary and comparison of the most recent literature on available and theorized treatment modalities for classic lattice corneal dystrophy (LCD). This paper aims to support practitioners in their management of this disease.

METHODS

A search was carried out on available literature through PubMed and Google Scholar of English language articles up to January 2023 that relate to the treatment of LCD. Due to scarcity of literature regarding specific novel therapies for LCD, results from other corneal pathologies (granular corneal dystrophy, corneal scarring) are sometimes included for contrast, which is clearly denoted.

RESULTS

LCD is a slowly progressive disease that leads to recurrent epithelial corneal erosions, stromal haze, corneal opacification, substantial discomfort, and visual impairment. Due to its autosomal-dominant inheritance pattern, this disease can persist throughout ancestral lines and requires consistent treatment and follow-up. An optimal management plan is necessary to (1) prolong years of life with best achievable visual acuity; (2) treat painful recurrent corneal erosions as they occur; (3) ensure proper follow-up throughout the life of a patient, as well as monitor at-risk offspring; and (4) monitor efficacy of treatment.

CONCLUSIONS

This paper addresses (1) treatment for early disease including corneal epithelial debridement, photo therapeutic keratectomy (PTK), femtosecond laser-assisted lamellar keratectomy (FLK), and others; (2) treatment for late disease including full thickness keratoplasties and anterior lamellar keratoplasties; and (3) potential future treatment considerations including a wide variety of topical/systemic, genetic, and regenerative approaches.

Selective Upregulation of Interleukin 1 Receptor Antagonist and Interleukin-8 in Fuchs' Endothelial Corneal Dystrophy with Accompanying Cataract

(1) Background: Patients with Fuchs' endothelial corneal dystrophy (FECD) may have coexisting cataracts and, therefore, may require a cataract surgery, which poses challenges due to potential endothelial cell damage. FECD is a degenerative eye disease of unclear etiology, with inflammatory cytokines maybe playing an important role in its development and progression. The present study aimed to investigate the cytokine profile in the aqueous humor of FECD eyes with cataract. (2) Methods: Fifty-two patients were included in the study, 26 with FECD + cataract and 26 with cataract as a control group. Samples of the aqueous humor were analyzed for pro- and anti-inflammatory cytokines using a Bio-Plex 200 system. (3) Results: Interleukin 1 receptor antagonist (IL-1Ra) and interleukin IL-8 levels were significantly higher in the aqueous humor of FECD + cataract patients compared to the control/cataract group. Moreover, the levels of anti-inflammatory IL-10 showed a strong trend to be higher in the FECD + cataract group compared to the control group. In contrast, there were no statistically significant differences in IL-1β, IL-6, IL-4, IL-10, IL-13, IL-17A, and tumor necrosis factor TNF-α between the groups. (4) Conclusions: Presented research contributes to a better understanding of FECD pathogenesis. Elevated levels of IL-1Ra and IL-8 may serve as a defense mechanism in people with FECD and coexisting cataract.

Epithelial recurrent erosion dystrophy (ERED) from the splice site altering COL17A1 variant c.3156C>T in families of Finnish-Swedish ancestry

PURPOSE

To describe four Finnish families with epithelial recurrent erosion dystrophy (ERED) caused by the pathogenic variant c.3156C>T in collagen type XVII alpha 1 chain gene (COL17A1).

METHODS

Eleven affected and two unaffected individuals underwent clinical ophthalmological examination, anterior segment photography, and corneal topography. Two of them underwent phototherapeutic keratectomy (PTK). Genetic analysis included both next-generation and Sanger sequencing. Specimens from the manual keratectomy of one patient were available for ophthalmic pathologic examination, including immunohistochemistry.

RESULTS

The common splice-site altering synonymous variant c.3156C > T, p.(Gly1052=) in COL17A1 was confirmed in 15 individuals with ERED from the four families. Subepithelial corneal scarring grades varied and increased with age, leading to decreased best-corrected visual acuity. PTK improved vision in 58- and 67-year-old individuals without reactivating the disease. The keratectomy specimens showed an uneven epithelium and a spectrum of basement membrane abnormalities, including breaks, fragmentation, multiplication and entrapment within the subepithelial scar, reflecting recurrent erosions. The stromal cells consisted of varying proportions of bland and activated fibroblasts and myofibroblasts, reflecting different ages of scars. The family with the largest number of known affected generations originated from Southern Sweden.

CONCLUSION

The phenotype in the Finnish ERED families is consistent with earlier reports of the c.3156C > T variant, although the severity has varied between reports. The phenotype may be modulated by other genes. This study suggests a likely founder effect of the variant in both Finnish and Swedish populations due to their shared population histories. If vision is compromised, PTK can be considered especially in older patients.

Unilateral Granular Type 2 Corneal Dystrophy With Exacerbation After LASIK

PURPOSE

The aim of this study was to report a case of unilateral granular corneal dystrophy type 2 (GCD2) with exacerbation after bilateral laser in situ keratomileusis (LASIK).

METHODS

Clinical evaluation, Scheimpflug imaging, anterior segment optical coherence tomography (AS-OCT), cytology, and genetic testing were used to confirm the diagnosis of unilateral GCD2 with exacerbation after bilateral LASIK. Detailed literature review for possible unilateral GCD2 presentations was performed.

RESULTS

A 54-year-old White woman presented with blurred vision in her left eye and a history of bilateral LASIK performed 8 years before. Examination revealed dense opacities in the left cornea only, which were confirmed to be confined to the LASIK interface and adjacent corneal stromal tissue, as determined by AS-OCT. The patient underwent flap lift, interface debris removal, and stromal bed phototherapeutic keratectomy. Cytological analysis showed eosinophilic corneal stromal deposits that stained with trichrome stain and were congophilic on Congo red stain. Genetic testing was positive for heterozygous GCD2 transforming growth factor β-induced gene ( TGFBI ), c.371G>A, p.R124H mutation. There were no opacities identifiable in the right eye on serial slit-lamp examination, Scheimpflug imaging, or OCT imaging at 4 or 8 years after bilateral LASIK. Literature review failed to identify any previous reports of unilateral GCD2.

CONCLUSIONS

This is the first known reported case of unilateral granular corneal dystrophy type 2. LASIK is contraindicated in eyes with corneal stromal dystrophies related to mutations in TGFBI as both flap creation and laser ablation can exacerbate visually significant opacity formation. Scheimpflug and AS-OCT imaging are useful to identify opacities in GCD2.

Mimicking TGFBI Hot-Spot Mutation Did Not Result in Any Deposit Formation in the Zebrafish Cornea

PURPOSE

Mutations in transforming growth factor beta-induced (TGFBI) protein are associated with a group of corneal dystrophies (CDs), classified as TGFBI-associated CDs, characterized by deposits in the cornea. Mouse models were not proper in several aspects for modelling human disease. The goal of this study was to generate zebrafish mutants to investigate the corneal phenotype and to decide whether zebrafish could be a potential model for TGFBI-associated CDs.

METHODS

The conserved arginine residue, codon 117, in zebrafish tgfbi gene was targeted with Clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 method. Cas9 VQR variant was used with two target-specific sgRNAs to generate mutations. The presence of mutations was evaluated by T7 Endonuclease Enzyme (T7EI) assay and the type of the mutations were evaluated by Sanger sequencing. The mutant zebrafish at 3 months and 1 year of age were investigated under the microscope for corneal opacity and eye sections were evaluated histopathologically with hematoxylin-eosin, masson-trichrome and congo red stains for corneal deposits.

RESULTS

We achieved indel variation at the target sequence that resulted in p.Ser115_Arg117delinsLeu (c. 347_353delinsT) by nonhomology mediated repair in F1. This zebrafish mutation had the potential to mimic two disease-causing mutations reported in human cases previously: R124L and R124L + del125-126. Mutant zebrafish did not show any corneal opacity or corneal deposits at 3 months and 1 year of age.

CONCLUSION

This study generated the first zebrafish model mimicking the R124 hot spot mutation in TGFBI-associated CDs. However, evaluations even at 1 year of age did not reveal any deposits in the cornea histopathologically. This study increased the cautions for modelling TGFBI-associated CDs in zebrafish in addition to differences in the corneal structure between zebrafish and humans.

Congenital stromal corneal dystrophy in a Spanish family: Clinical, genetic and histological analysis

PURPOSE

To present the clinical, genetic, and histopathological features of the ninth family affected by congenital stromal corneal dystrophy (CSCD) to date.

METHODS

Twelve cases of a Spanish family affected by CSCD were analyzed regarding history, visual acuity (VA, decimal scale), an ophthalmologic exam and specular microscopy. Five eyes were treated by deep anterior lamellar keratoplasty (DALK), and thirteen eyes by penetrating keratoplasty (PK). In the two last generations, a genetic study was performed.

RESULTS

Most of the patients affected were born with opaque corneas except for three, whose corneas were clear at birth. Biomicroscopy showed a whitish diffuse stromal opacity with an unaltered epithelium, causing poor VA (from hand motions to 0.4). Patients treated with PK presented mean postoperative VA of 0.19±0.20 over a follow-up time of 235.3±101.4months with 38% recurrences. Patients who underwent DALK experienced VA improvement to 0.17±0.11 over a follow-up time of 10.8±2.6months without signs of recurrence. In the latter, the big bubble technique was not achieved, so a manual technique was performed. The genetic study showed heterozygosis for a 1-bp deletion at nucleotide 962 in exon 8 of the decorin gene.

CONCLUSIONS

CSCD is a rare entity, which should be treated by DALK whenever possible, obtaining better results than PK. Close monitoring of children of affected individuals is important, because CSCD can progress during the early years of life.

IC3D Classification of Corneal Dystrophies-Edition 3

PURPOSE

The International Committee for the Classification of Corneal Dystrophies (IC3D) was created in 2005 to develop a new classification system integrating current information on phenotype, histopathology, and genetic analysis. This update is the third edition of the IC3D nomenclature.

METHODS

Peer-reviewed publications from 2014 to 2023 were evaluated. The new information was used to update the anatomic classification and each of the 22 standardized templates including the level of evidence for being a corneal dystrophy [from category 1 (most evidence) to category 4 (least evidence)].

RESULTS

Epithelial recurrent erosion dystrophies now include epithelial recurrent erosion dystrophy, category 1 ( COL17A1 mutations, chromosome 10). Signs and symptoms are similar to Franceschetti corneal dystrophy, dystrophia Smolandiensis, and dystrophia Helsinglandica, category 4. Lisch epithelial corneal dystrophy, previously reported as X-linked, has been discovered to be autosomal dominant ( MCOLN1 mutations, chromosome 19). Classic lattice corneal dystrophy (LCD) results from TGFBI R124C mutation. The LCD variant group has over 80 dystrophies with non-R124C TGFBI mutations, amyloid deposition, and often similar phenotypes to classic LCD. We propose a new nomenclature for specific LCD pathogenic variants by appending the mutation using 1-letter amino acid abbreviations to LCD. Pre-Descemet corneal dystrophies include category 1, autosomal dominant, punctiform and polychromatic pre-Descemet corneal dystrophy (PPPCD) ( PRDX3 mutations, chromosome 10). Typically asymptomatic, it can be distinguished phenotypically from pre-Descemet corneal dystrophy, category 4. We include a corneal dystrophy management table.

CONCLUSIONS

The IC3D third edition provides a current summary of corneal dystrophy information. The article is available online at https://corneasociety.org/publications/ic3d .

Novel Manifestation of Corneal Dystrophy After Keratorefractive Surgery

PURPOSE

This study aimed to report cases of bilateral corneal Bowman layer deposits in 4 patients with a history of keratorefractive surgery. To our knowledge, this condition has not previously been reported and should be distinguished from granular corneal dystrophy type 2 and other corneal dystrophies.

METHODS

We reviewed all available medical records that were collected between January 2010 and December 2021 at a tertiary referral center and performed whole-exome sequencing to provide diagnostic information.

RESULTS

Four patients exhibited similar bilateral corneal deposits that were observed more than 10 years after keratorefractive surgery. The patients' ages ranged from 36 to 53 years; 3 of the 4 patients were female. Three patients received laser in situ keratomileusis surgery, and 1 received radial keratotomy. All 4 patients denied having a family history of ocular diseases and reported an uneventful postoperative course. On examination, the best-corrected visual acuity ranged from 6/10 to 6/6 in all 4 patients. Slit-lamp examination revealed bilateral superficial corneal deposits involving the central cornea, and anterior segment optical coherence tomography revealed hyperreflective deposits located in the Bowman layer. Such unique manifestations suggested corneal dystrophy; thus, whole-exome sequencing was performed on all 4 patients. Only 1 patient exhibited a missense mutation in TGFBI . We further analyzed common de novo mutations to explore possible candidate genes associated with this presentation.

CONCLUSIONS

We report a rare entity of presumed corneal dystrophy with deposits located in the Bowman layer in 4 patients who had received keratorefractive surgery. Clarifying the underlying pathophysiology and genetic predisposition of this disease may aid in diagnosing and preventing potential complications after keratorefractive surgery.

Clinical and Optical Coherence Tomography Correlation of Recurrence Patterns After Femtosecond Laser-Assisted Anterior Lamellar Keratoplasty in Reis-Bucklers Corneal Dystrophy

PURPOSE

The aim of this study was to report the clinical profile and patterns of recurrence after femtosecond laser-assisted anterior lamellar keratoplasty (FALK) in Reis-Bucklers corneal dystrophy.

METHODS

This is a case series of 5 eyes of 4 patients with Reis-Bucklers corneal dystrophy. Clinical images of recurrence were correlated with the high-resolution optical coherence tomography. Histopathologic examination of excised corneal samples was performed when possible.

RESULTS

The median time to recurrence was 2 (1-5) years after FALK. Of the 5 eyes, 1 eye had primary FALK, whereas 4 eyes had secondary interventions, which included previous phototherapeutic keratectomy (once in 1 eye and twice in 2 eyes), and previous penetrating keratoplasty, followed by phototherapeutic keratectomy (1 eye). Recurrence was noted at the level of the subepithelium. In addition, 1 eye showed interface deposits along with epithelial downgrowth at the graft-host bed.

CONCLUSIONS

The 2 distinct patterns of recurrence noted were at the subepithelial region and the interface. The clinical patterns of recurrence favor an epithelial origin of recurrent deposits.

[Corneal wound healing-Pharmacological treatment]

Physiological wound healing of the cornea is a complex process and involves numerous multifactorial tissue processes. A proper wound healing, especially without the formation of light-scattering scars, is essential to preserve the integrity and function of the cornea. Misdirected wound healing is of vast clinical relevance as it can lead to corneal fibrosis and the loss of optical transparency with subsequent reduction of visual acuity, up to blindness. In addition to the understanding of the pathophysiological mechanisms, the knowledge of therapeutic concepts and options for treating corneal wound healing disorders and fibrosis is essential to counteract a permanent damage of the cornea as early as possible. Nowadays, various pharmacological and surgical options are available for treatment. The decision, appropriate selection and indication for the optimal treatment depend primarily on the genesis and clinical appearance of the corneal wound, fibrosis or scar. The treatment of wound healing disorders ranges from the use of topical therapy and supportive measures up to tissue replacement procedures. As long as the mechanical stability of the cornea is intact and wound healing processes are still ongoing, a pharmacological modulation is reasonable, which is discussed in this article.

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.

Synergistic Effect of Nilavembu Choornam-Gold Nanoparticles on Antibiotic-Resistant Bacterial Susceptibility and Contact Lens Contamination-Associated Infectious Pathogenicity

Antibiotic-resistant bacterial colonies mitigate rapid biofilm formation and have complex cell wall fabrications, making it challenging to penetrate drugs across their biofilm barriers. The objective of this study was to investigate the antibacterial susceptibility of antibiotic-resistant bacteria and contact lens barrenness. Nilavembu Choornam-Gold Nanoparticles (NC-GNPs) were synthesized using NC polyherbal extract and characterized by UV-visible spectrophotometer, SEM-EDX, XRD, Zeta sizer, FTIR, and TEM analysis. Contact lenses with overnight cultures of antibiotic-resistant bacteria K. pneumoniae and S. aureus showed significant differences in growth, biofilm formation, and infection pathogenicity. The NC-GNPs were observed in terms of size (average size is 57.6 nm) and surface chemistry. A zone of inhibition was calculated for K. pneumoniae 18.8 ± 1.06, S. aureus 23.6 ± 1.15, P. aeruginosa 24.16 ± 0.87, and E. faecalis 24.5 ± 1.54 mm at 24 h of NC-GNPs alone treatment. In electron microscopy studies, NC-GNP-treated groups showed nuclear shrinkage, nuclear disintegration, degeneration of cell walls, and inhibited chromosomal division. In contrast, normal bacterial colonies had a higher number of cell divisions and routinely migrated toward cell multiplications. NC-GNPs exhibited antibacterial efficacy against antibiotic-resistant bacteria when compared to NC extract alone. We suggest that NC-GNPs are highly valuable to the population of hospitalized patients and other people to reduce the primary complications of contact lens contamination-oriented microbial infection and the therapeutic efficiency of antibiotic-resistant bacterial pathogenicity.

Lisch Epithelial Corneal Dystrophy Is Caused by Heterozygous Loss-of-Function Variants in MCOLN1

PURPOSE

To report the genetic etiology of Lisch epithelial corneal dystrophy (LECD).

DESIGN

Multicenter cohort study.

METHODS

A discovery cohort of 27 individuals with LECD from 17 families, including 7 affected members from the original LECD family, 6 patients from 2 new families and 14 simplex cases, was recruited. A cohort of 6 individuals carrying a pathogenic MCOLN1 (mucolipin 1) variant was reviewed for signs of LECD. Next-generation sequencing or targeted Sanger sequencing were used in all patients to identify pathogenic or likely pathogenic variants and penetrance of variants.

RESULTS

Nine rare heterozygous MCOLN1 variants were identified in 23 of 27 affected individuals from 13 families. The truncating nature of 7 variants and functional testing of 1 missense variant indicated that they result in MCOLN1 haploinsufficiency. Importantly, in the homozygous and compound-heterozygous state, 4 of 9 LECD-associated variants cause the rare lysosomal storage disorder mucolipidosis IV (MLIV). Autosomal recessive MLIV is a systemic disease and comprises neurodegeneration as well as corneal opacity of infantile-onset with epithelial autofluorescent lysosomal inclusions. However, the 6 parents of 3 patients with MLIV confirmed to carry pathogenic MCOLN1 variants did not have the LECD phenotype, suggesting MCOLN1 haploinsufficiency may be associated with reduced penetrance and variable expressivity.

CONCLUSIONS

MCOLN1 haploinsufficiency is the major cause of LECD. Based on the overlapping clinical features of corneal epithelial cells with autofluorescent inclusions reported in both LECD and MLIV, it is concluded that some carriers of MCOLN1 haploinsufficiency-causing variants present with LECD.

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.

Ocular Pathology and Genetics: Transformative Role of Artificial Intelligence (AI) in Anterior Segment Diseases

Artificial intelligence (AI) has become a revolutionary influence in the field of ophthalmology, providing unparalleled capabilities in data analysis and pattern recognition. This narrative review delves into the crucial role that AI plays, particularly in the context of anterior segment diseases with a genetic basis. Corneal dystrophies (CDs) exhibit significant genetic diversity, manifested by irregular substance deposition in the cornea. AI-driven diagnostic tools exhibit promising accuracy in the identification and classification of corneal diseases. Importantly, chat generative pre-trained transformer (ChatGPT)-4.0 shows significant advancement over its predecessor, ChatGPT-3.5. In the realm of glaucoma, AI significantly contributes to precise diagnostics through inventive algorithms and machine learning models, surpassing conventional methods. The incorporation of AI in predicting glaucoma progression and its role in augmenting diagnostic efficiency is readily apparent. Additionally, AI-powered models prove beneficial for early identification and risk assessment in cases of congenital cataracts, characterized by diverse inheritance patterns. Machine learning models achieving exceptional discrimination in identifying congenital cataracts underscore AI's remarkable potential. The review concludes by emphasizing the promising implications of AI in managing anterior segment diseases, spanning from early detection to the tailoring of personalized treatment strategies. These advancements signal a paradigm shift in ophthalmic care, offering optimism for enhanced patient outcomes and more streamlined healthcare delivery.

Investigation of the functional impact of CHED- and FECD4-associated SLC4A11 mutations in human corneal endothelial cells

Mutations in the solute linked carrier family 4 member 11 (SLC4A11) gene are associated with congenital hereditary endothelial dystrophy (CHED) and Fuchs corneal endothelial dystrophy type 4 (FECD4), both characterized by corneal endothelial cell (CEnC) dysfunction and/or cell loss leading to corneal edema and visual impairment. In this study, we characterize the impact of CHED-/FECD4-associated SLC4A11 mutations on CEnC function and SLC4A11 protein localization by generating and comparing human CEnC (hCEnC) lines expressing wild type SLC4A11 (SLC4A11WT) or mutant SLC4A11 harboring CHED-/FECD4-associated SLC4A11 mutations (SLC4A11MU). SLC4A11WT and SLC4A11MU hCEnC lines were generated to express either SLC4A11 variant 2 (V2WT and V2MU) or variant 3 (V3WT and V3MU), the two major variants expressed in ex vivo hCEnC. Functional assays were performed to assess cell barrier, proliferation, viability, migration, and NH3-induced membrane conductance. We demonstrate SLC4A11-/- and SLC4A11MU hCEnC lines exhibited increased migration rates, altered proliferation and decreased cell viability compared to SLC4A11WT hCEnC. Additionally, SLC4A11-/- hCEnC demonstrated decreased cell-substrate adhesion and membrane capacitances compared to SLC4A11WT hCEnC. Induction with 10mM NH4Cl led SLC4A11WT hCEnC to depolarize; conversely, SLC4A11-/- hCEnC hyperpolarized and the majority of SLC4A11MU hCEnC either hyperpolarized or had minimal membrane potential changes following NH4Cl induction. Immunostaining of primary hCEnC and SLC4A11WT hCEnC lines for SLC4A11 demonstrated predominately plasma membrane staining with poor or partial colocalization with mitochondrial marker COX4 within a subset of punctate subcellular structures. Overall, our findings suggest CHED-associated SLC4A11 mutations likely lead to hCEnC dysfunction, and ultimately CHED, by interfering with cell migration, proliferation, viability, membrane conductance, barrier function, and/or cell surface localization of the SLC4A11 protein in hCEnC. Additionally, based on their similar subcellular localization and exhibiting similar cell functional profiles, protein isoforms encoded by SLC4A11 variant 2 and variant 3 likely have highly overlapping functional roles in hCEnC.

Microbial keratitis in lattice corneal dystrophy: microsporidia as a new cause

A patient in his sixth decade presented to us with redness, pain and a deterioration of vision in his left eye. He had previously been diagnosed with lattice corneal dystrophy (LCD). He was diagnosed with microbial keratitis, and mixed infection was confirmed on culture (bacteria and fungus) with a protracted healing period before resolution of keratitis. He presented 2 years later with similar issues in the same eye and was noted to have a second episode of microbial keratitis, with microsporidia spores noted on gram, potassium hydroxide and calcofluor white stains. He was diagnosed with microsporidial stromal keratitis and underwent therapeutic penetrating keratoplasty. Unfortunately, he suffered a recurrence of microsporidial keratitis following surgery with eventual transplant failure. Microsporidia as an infection in LCD has, to our knowledge, not been previously reported. We aim to discuss microsporidial infection and recurrent microbial keratitis in the setting of LCD.

[Modern corneal diagnostics as the key for the correct classification of the disease and optimal treatment decisions]

Corneal diseases include a wide spectrum of different manifestations (inflammatory/noninflammatory) that need to be accurately classified for precise diagnosis and targeted treatment. In addition to the anamnesis and slit lamp biomicroscopy, further device-based examinations can be performed to narrow down the diagnosis. Nowadays, modern corneal imaging provides a variety of technologies, such as topography, tomography, in vivo confocal microscopy and analysis of biomechanics, which are able to reliably classify different pathologies. Knowledge of the available examination modalities helps to guide differential diagnostic considerations, facilitating the indication for stage-appropriate microsurgical intervention.

Systematic Review of the Diagnostic Criteria and Severity Classification for Fuchs Endothelial Corneal Dystrophy

PURPOSE

There are no defined diagnostic criteria and severity classification for Fuchs endothelial corneal dystrophy (FECD), which are required for objective standardized assessments. Therefore, we performed a systematic literature review of the current diagnosis and severity classification of FECD.

METHODS

We searched the Ovid MEDLINE and Web of Science databases for studies published until January 13, 2021. We excluded review articles, conference abstracts, editorials, case reports with <5 patients, and letters.

RESULTS

Among 468 articles identified, we excluded 173 and 165 articles in the first and second screenings, respectively. Among the 130 included articles, 61 (47%) and 99 (76%) mentioned the diagnostic criteria for FECD and described its severity classification, respectively. Regarding diagnosis, slitlamp microscope alone was the most frequently used device in 31 (51%) of 61 articles. Regarding diagnostic findings, corneal guttae alone was the most common parameter [adopted in 23 articles (38%)]. Regarding severity classification, slitlamp microscopes were used in 88 articles (89%). The original or modified Krachmer grading scale was used in 77 articles (78%), followed by Adami's classification in six (6%). Specular microscopes or Scheimpflug tomography were used in four articles (4%) and anterior segment optical coherence tomography in one (1%).

CONCLUSIONS

FECD is globally diagnosed by the corneal guttae using slitlamp examination, and its severity is predominantly determined by the original or modified Krachmer grading scale. Objective severity grading using Scheimpflug or anterior segment optical coherence tomography can be applied in the future innovative therapies such as cell injection therapy or novel small molecules.

Corneal Copper Deposition Secondary to Monoclonal Gammopathy in a Patient With Chronic Lymphocytic Leukemia: A Case Report

Hypercupremia-induced corneal copper deposition secondary to monoclonal gammopathy is rare and shows a characteristic corneal opacity quite different from other causes of hypercupremia, such as Wilson's disease. This report describes a case of corneal copper deposition in a patient with monoclonal gammopathy associated with chronic lymphocytic leukemia. An 84-year-old man with slowly progressive corneal opacity was referred to our hospital. The corneal opacity was present at least five years ago. The patient's best-corrected visual acuity was 20/25 OU (in both eyes) at the initial visit to our hospital. Slit-lamp examination and anterior segment optical coherence tomography revealed bilateral brown-colored opacity localized to deep layers of the central cornea. In vivo confocal microscopy (IVCM) showed indistinct corneal stromal cells in the deep layer and endothelial cells. The possible differential diagnoses were corneal dystrophy and Wilson's disease, but the color, shape, or site of corneal opacity was inconsistent with the disease. As the patient had a history of chronic lymphocytic leukemia, which is often associated with monoclonal gammopathy, we suspected that the corneal opacity was copper deposition in association with the hematologic diseases. Laboratory examinations showed elevated serum copper and normal ceruloplasmin. Serum protein electrophoresis revealed significantly high IgG levels with depression of IgA, IgE, and IgM. These results supported our diagnosis. Followingly, we consulted the patient's attending hematologist, and the doctor initiated treatment for hypercupremia. In conclusion, hypercupremia secondary to monoclonal gammopathy should be considered a possible cause of central brown-colored corneal opacity.

A Novel Heterozygous TGFBI c.1613C>A Pathogenic Variant is Associated With Lattice Corneal Dystrophy in a Chinese Family

PURPOSE

To investigate the gene mutations and relationship of clinical manifestation in a Chinese family with familial lattice corneal dystrophy (LCD).

DESIGN

Single-family case-control study.

METHODS

A family with familial LCD was recruited for this study. A total of 10 affected and 13 healthy family members participated in this research. Clinical features were examined by slit-lamp examination and anterior segment optical coherence tomography (AS-OCT). Peripheral blood samples were collected from each participant, and genomic DNA was extracted. Whole-exome sequencing (WES) analysis was performed, and the pathogenic variants of LCD were identified using bioinformatics tools and confirmed by Sanger sequencing.

RESULTS

Slit-lamp examination revealed diffuse grayish-white punctate, linear, and "lattice-like" opacities in the corneal epithelium and superficial corneal stroma. AS-OCT revealed an irregularly shaped cornea. The corneal epithelium and anterior corneal stroma showed high-reflective deposits and bulges. The clinical appearance of the patients fit the pattern and features of autosomal dominant inheritance of LCD type I (LCD I). A novel pathogenic variant of exon 12 in TGFBI was found by WES analysis, in which cytosine at position 1613 was substituted by adenine (c.1613C>A), and the amino acid was changed from threonine to lysine (p.T538K). Mutated genes and proteins were predicted to be deleterious.

CONCLUSION

A novel heterozygous pathogenic variant (c.1613C>A) of TGFBI was identified in the Chinese family with LCD I.

Animal Models in Eye Research: Focus on Corneal Pathologies

The eye is a complex sensory organ that enables visual perception of the world. The dysfunction of any of these tissues can impair vision. Conduction studies on laboratory animals are essential to ensure the safety of therapeutic products directly applied or injected into the eye to treat ocular diseases before eventually proceeding to clinical trials. Among these tissues, the cornea has unique homeostatic and regenerative mechanisms for maintaining transparency and refraction of external light, which are essential for vision. However, being the outermost tissue of the eye and directly exposed to the external environment, the cornea is particularly susceptible to injury and diseases. This review highlights the evidence for selecting appropriate animals to better understand and treat corneal diseases, which rank as the fifth leading cause of blindness worldwide. The development of reliable and human-relevant animal models is, therefore, a valuable research tool for understanding and translating fundamental mechanistic findings, as well as for assessing therapeutic potential in humans. First, this review emphasizes the unique characteristics of animal models used in ocular research. Subsequently, it discusses current animal models associated with human corneal pathologies, their utility in understanding ocular disease mechanisms, and their role as translational models for patients.

Pathogenicity and Function Analysis of Two Novel SLC4A11 Variants in Patients With Congenital Hereditary Endothelial Dystrophy

Purpose

The purpose of this study was to explore the pathogenicity and function of two novel SLC4A11 variants associated with congenital hereditary endothelial dystrophy (CHED) and to study the function of a SLC4A11 (K263R) mutant in vitro.

Methods

Ophthalmic examinations were performed on a 28-year-old male proband with CHED. Whole-exome and Sanger sequencing were applied for mutation screening. Bioinformatics and pathogenicity analysis were performed. HEK293T cells were transfected with the plasmids of empty vector, wild-type SLC4A11, and SLC4A11 (K263R) mutant. The transfected cells were treated with SkQ1. Oxygen consumption, cellular reactive oxygen species (ROS) level, mitochondrial membrane potential, and apoptosis rate were measured.

Results

The proband had poor visual acuity with nystagmus since childhood. Corneal foggy opacity was evident in both eyes. Two novel SLC4A11 variants were detected. Sanger sequencing showed that the proband's father and sister carried c.1464-1G>T variant, and the proband's mother and sister carried c.788A>G (p.Lys263Arg) variant. Based on the American College of Medical Genetics (ACMG) guidelines, SLC4A11 c.1464-1G>T was pathogenic, whereas c.788A>G, p.K263R was a variant of undetermined significance. In vitro, SLC4A11 (K263R) variant increased ROS level and apoptosis rate. Decrease in mitochondrial membrane potential and oxygen consumption rate were remarkable. Furthermore, SkQ1 decreased ROS levels and apoptosis rate but increased mitochondrial membrane potential in the transfected cells.

Conclusions

Two novel heterozygous pathogenic variants of the SLC4A11 gene were identified in a family with CHED. The missense variant SLC4A11 (K263R) caused mitochondrial dysfunction and increased apoptosis in mutant transfected cells. In addition, SkQ1 presented a protective effect suggesting the anti-oxidant might be a novel therapeutic drug.

Translational Relevance

This study verified the pathogenicity of 2 novel variants in the SLC4A11 gene in a CHED family and found an anti-oxidant might be a new drug.

Updates on congenital hereditary endothelial dystrophy

Congenital hereditary endothelial dystrophy (CHED) is a rare genetic corneal disorder causing progressive cornea clouding and significant visual impairment. CHED remains a leading indication for pediatric corneal transplantation despite its infrequency, particularly in regions with high consanguinity rates like Southeast Asia. Identifying the Solute Carrier Family 4 Member 11 (SLC4A11) gene as the genetic basis of CHED has led to the discovery of it's various genetic variations. However, a comprehensive understanding of its clinical-genetic correlation, pathophysiology, and optimal management is ongoing. This review aims to consolidate current knowledge about CHED, covering its genetic origins, pathophysiological mechanisms, clinical presentation, and management strategies. Surgical intervention, such as penetrating keratoplasty (PK), Descemet stripping automated endothelial keratoplasty (DSAEK), and Descemet membrane endothelial keratoplasty (DMEK), remains the primary treatment. DSAEK and DMEK offer advantages over PK, including quicker visual recovery, reduced complications, and longer graft survival, especially in the pediatric age group. The timing of surgical interventions depends on disease severity, age at presentation, comorbidities, and visual potential. Elevated oxidative stress in CHED corneal tissue suggests potential benefits from anti-inflammatory drugs to rescue mutated endothelial cells. Considering the limitations of corneal graft surgeries, exploring novel gene-based molecular therapies are essential for future management. Early diagnosis, appropriate surgical interventions, amblyopia control, and genetic counseling for predictive analysis are pivotal for optimizing CHED management. A multidisciplinary approach involving ophthalmologists, researchers, and genetic counselors is essential for precise diagnosis and optimal care for CHED patients.

Matrix Metalloproteinases and the Pathogenesis of Recurrent Corneal Erosions and Epithelial Basement Membrane Dystrophy

Matrix metalloproteinases (MMPs) are a group of proteolytic enzymes which are members of the zinc endopeptidase family. They have the ability to degrade extracellular matrix elements, allowing for the release of binding molecules and cell migration. Although metalloproteinases regulate numerous physiological processes within the cornea, overexpression of metalloproteinase genes and an imbalance between the levels of metalloproteinases and their inhibitors can contribute to the inhibition of repair processes, the development of inflammation and excessive cellular proliferation. The involvement of MMPs in the pathogenesis of dystrophic corneal diseases needs clarification. Our analyses focus on the involvement of individual metalloproteinases in the pathogenesis of recurrent corneal erosions and highlight their impact on the development of corneal epithelial basement membrane dystrophy (EBMD). We hypothesize that abnormalities observed in patients with EBMD may result from the accumulation and activation of metalloproteinases in the basal layers of the corneal epithelium, leading to basement membrane degradation. A barrier formed from degradation materials inhibits the normal migration of epithelial cells to the superficial layers, which contributes to the development of the aforementioned lesions. This hypothesis seems to be lent support by the elevated concentrations of metalloproteinases in the corneal epithelium of these patients found in our previous studies on the relationships between MMPs and recurrent corneal erosions.

Endoplasmic reticulum stress: molecular mechanism and therapeutic targets

The endoplasmic reticulum (ER) functions as a quality-control organelle for protein homeostasis, or "proteostasis". The protein quality control systems involve ER-associated degradation, protein chaperons, and autophagy. ER stress is activated when proteostasis is broken with an accumulation of misfolded and unfolded proteins in the ER. ER stress activates an adaptive unfolded protein response to restore proteostasis by initiating protein kinase R-like ER kinase, activating transcription factor 6, and inositol requiring enzyme 1. ER stress is multifaceted, and acts on aspects at the epigenetic level, including transcription and protein processing. Accumulated data indicates its key role in protein homeostasis and other diverse functions involved in various ocular diseases, such as glaucoma, diabetic retinopathy, age-related macular degeneration, retinitis pigmentosa, achromatopsia, cataracts, ocular tumors, ocular surface diseases, and myopia. This review summarizes the molecular mechanisms underlying the aforementioned ocular diseases from an ER stress perspective. Drugs (chemicals, neurotrophic factors, and nanoparticles), gene therapy, and stem cell therapy are used to treat ocular diseases by alleviating ER stress. We delineate the advancement of therapy targeting ER stress to provide new treatment strategies for ocular diseases.

[Corneal disease in childhood-Hereditary, degenerative or infectious?]

BACKGROUND

Adequate visual acuity significantly contributes to the age-appropriate development of children's neurobehavior. Infantile corneal opacities are rare but implicate a high potential for amblyopia.

OBJECTIVE

This review aims to provide an overview of the most common causes of infantile corneal opacities and highlights ophthalmopathological correlations.

METHODS

The following review is based on an extensive literature search.

RESULTS

If metabolic diseases, traumatic or infectious events can be excluded as a cause for an infantile corneal opacity, it is important to focus on the 3Ds, corneal dysgenesis, corneal dystrophy or corneal degeneration.

DISCUSSION

If corneal opacities occur in childhood, early recognition, diagnosis, and initiation of treatment, including prophylaxis of amblyopia, are of utmost importance. In unexplained corneal opacities the histopathological work-up of the explanted cornea can contribute to the final diagnosis.

Anterior Segment Swept Source Optical Coherence Tomography and In Vivo Confocal Microscopy Findings in a Case With Bleb-Like Epithelial Basal Membrane Dystrophy

PURPOSE

The aim of this study was to evaluate the anterior segment swept source optical coherence tomography (SS-OCT) and in vivo confocal microscopy (IVCM) features in a patient with bleb-like epithelial basement membrane dystrophy (EBMD).

METHODS

A 67-year-old man was referred to the hospital for recurrent attacks of severe ocular pain, tearing, and photophobia, typically upon awakening in the right eye. Biomicroscopic examination revealed pebbled glass-like appearance in the corneal epithelium which was remarkable with retroillumination and the patient was suspected to have bleb-like EBMD. The cornea was further evaluated using SS-OCT DRI Triton (Topcon, Tokyo, Japan) and IVCM (Heidelberg Retina Tomograph 3, Rostock Cornea Module).

RESULTS

Using anterior segment SS-OCT, multiple, hyporeflective, round-oval structures within the size range of 30 to 90 μm were observed at the basal epithelial level. IVCM showed circular or oval hyporeflective areas with a diameter ranging from 30 to 140 μm at the level of the basal epithelium in a depth of 35 to 40 μm from the corneal surface and hyperreflective linear structures extending into the corneal epithelium. The corneal stroma was normal, while a few round hyperreflective deposits and guttae were noted at the endothelial cell layer.

CONCLUSIONS

Anterior segment SS-OCT and IVCM can be used in the diagnosis of bleb-like EBMD and are very helpful in differentiating from other epithelial/subepithelial corneal dystrophies and cystic disorders of the corneal epithelium.

Mini-Review: Clinical Features and Management of Granular Corneal Dystrophy Type 2

Granular corneal dystrophy type 2 (GCD2) is an autosomal dominant corneal stromal dystrophy that is caused by p.Arg124His mutation of transforming growth factor β induced (TGFBI) gene. It is characterized by well demarcated granular shaped opacities in central anterior stroma and as the disease progresses, extrusion of the deposits results in ocular pain due to corneal epithelial erosion. Also, diffuse corneal haze which appears late, causes decrease in visual acuity. The prevalence of GCD2 is high in East Asia including Korea. Homozygous patients show a severe phenotype from an early age, and the heterozygote phenotype varies among patients, depending on several types of compound heterozygous TGFBI mutations. In the initial stage, conservative treatments such as artificial tears, antibiotic eye drops, and bandage contact lenses are used to treat corneal erosion. Different surgical methods are used depending on the depth and extent of the stromal deposits. Phototherapeutic keratectomy removes anterior opacities and is advantageous in terms of its applicability and repeatability. For deeper lesions, deep anterior lamellar keratoplasty can be used as the endothelial layer is not always affected. Recurrence following these treatments are reported within a wide range of rates in different studies due to varying definition of recurrence and follow-up period. In patients who have undergone corneal laser vision-correction surgeries such as photorefractive keratectomy, LASEK, or LASIK including SMILE surgery, corneal opacity exacerbates rapidly with severe deterioration of visual acuity. Further investigations on new treatments of GCD2 are necessary.

The mTOR signalling in corneal diseases: A recent update

Corneal diseases affect 4.2 million people worldwide and are a leading cause of vision impairment and blindness. Current treatments for corneal diseases, such as antibiotics, steroids, and surgical interventions, have numerous disadvantages and challenges. Thus, there is an urgent need for more effective therapies. Although the pathogenesis of corneal diseases is not fully understood, it is known that injury caused by various stresses and postinjury healing, such as epithelial renewal, inflammation, stromal fibrosis, and neovascularization, are highly involved. Mammalian target of rapamycin (mTOR) is a key regulator of cell growth, metabolism, and the immune response. Recent studies have revealed that activation of mTOR signalling extensively contributes to the pathogenesis of various corneal diseases, and inhibition of mTOR with rapamycin achieves promising outcomes, supporting the potential of mTOR as a therapeutic target. In this review, we detail the function of mTOR in corneal diseases and how these characteristics contribute to disease treatment using mTOR-targeted drugs.

Oxidative Stress and Cellular Protein Accumulation Are Present in Keratoconus, Macular Corneal Dystrophy, and Fuchs Endothelial Corneal Dystrophy

The aim of the study was to investigate oxidative stress as well as cellular protein accumulation in corneal diseases including keratoconus (KC), macular corneal dystrophy (MCD), and Fuchs endothelial corneal dystrophy (FECD) at their primary affecting sites. Corneal buttons from KC, MCD, and FECD patients, as well as healthy controls, were analyzed immunohistochemically to evaluate the presence of oxidative stress and the function of the proteostasis network. 4-Fydroxynonenal (4-HNE) was used as a marker of oxidative stress, whereas the levels of catalase and heat-shock protein 70 (HSP70) were analyzed to evaluate the response of the antioxidant defense system and molecular chaperones, respectively. Sequestosome 1 (SQSTM1) levels were determined to assess protein aggregation and the functionality of autophagic degradation. Basal epithelial cells of the KC samples showed increased levels of oxidative stress marker 4-HNE and antioxidant enzyme catalase together with elevated levels of HSP70 and accumulation of SQSTM1. Corneal stromal cells and endothelial cells from MCD and FECD samples, respectively, showed similarly increased levels of these markers. All corneal diseases showed the presence of oxidative stress and activation of the molecular chaperone response to sustain protein homeostasis. However, the accumulation of protein aggregates suggests insufficient function of the protective mechanisms to limit the oxidative damage and removal of protein aggregates via autophagy. These results suggest that oxidative stress has a role in KC, MCD, and FECD at the cellular level as a secondary outcome. Thus, antioxidant- and autophagy-targeted therapies could be included as supporting care when treating KC or corneal dystrophies.

[Human genetic diagnostics in hereditary eye diseases : What does the ophthalmologist need to know]

Hereditary eye disorders can affect all ocular structures and can be accompanied by structural malformations (e.g. coloboma) or functional disorders (e.g. retinal dystrophy). Ocular phenotypes can also be the presenting symptom of many complex syndromic disorders. The majority of hereditary eye disorders are extremely heterogeneous but can be routinely diagnosed by modern high-throughput sequencing technologies. Molecular testing is highly important not only in in the evaluation of differential diagnoses but is also of increasing relevance due to individual treatment options.

Sequential Custom Therapeutic Keratectomy for the Treatment of Granular Corneal Dystrophy Type 1: A Long-term Study

PURPOSE

To evaluate the effectiveness of sequential custom phototherapeutic keratectomy (SCTK) for granular corneal dystrophy type 1 (GCD1).

METHODS

Thirty-seven eyes of 21 patients with GCD1 were treated with SCTK to remove superficial opacifications, regularize the corneal surface, and decrease optical aberrations. SCTK is a sequence of custom therapeutic excimer laser keratectomies with step-by-step intraoperative corneal topography monitoring of results. Six eyes of 5 patients previously treated with penetrating keratoplasty received SCTK for disease recurrence. Pre-operative and postoperative corrected distance visual acuity (CDVA), refractive values, mean pupillary keratometry, and pachymetry were retrospectively analyzed. The mean follow-up period was 41.3 months.

RESULTS

SCTK provided significant decimal CDVA improvement, from 0.33 ± 0.22 to 0.63 ± 0.24 (P < .0001) at the last available follow-up visit. One eye, initially treated with penetrating keratoplasty, showed visually significant disease 8 years after the first SCTK and was re-treated. Mean corneal pachymetry difference between preoperative and final follow-up values was 78.42 ± 62.26 µm. Mean corneal curvature and the spherical component did not show a statistically significant change or hyperopic shift. Astigmatism and higher order aberration reduction were statistically significant.

CONCLUSIONS

SCTK is a powerful tool for the treatment of anterior corneal pathologies hindering vision and quality of life, such as GCD1. SCTK is less invasive and fosters more rapid visual recovery than penetrating keratoplasty or deep anterior lamellar keratoplasty. Providing significant visual improvement, SCTK can be the preferred initial treatment in eyes with GCD1. [J Refract Surg. 2023;39(6):422-429.].

New Endothelial Corneal Dystrophy in a Chinese Family

PURPOSE

The aim of this study was to characterize the clinical presentation of atypical endothelial corneal dystrophy (ECD) and to identify possible associated genetic variants in a Chinese family.

METHODS

Six affected members, 4 unaffected first-degree relatives, and 3 spouses who were enrolled in this study underwent ophthalmic examinations. Genetic linkage analysis was performed for 4 affected and 2 unaffected members, and whole-exome sequencing (WES) was performed for 2 patients to identify disease-causing variants. Candidate causal variants were verified using Sanger sequencing in family members and 200 healthy controls.

RESULTS

The mean age at disease onset was 16.5 years. The early phenotype of this atypical ECD was characterized by multiple small white translucent spots located in Descemet membrane of the peripheral cornea. These spots coalesced to form opacities with variable shapes, and eventually merged along the limbus. Subsequently, translucent spots appeared in central Descemet membrane and accumulated, causing diffuse polymorphous opacities over time. Finally, significant endothelial decompensation led to diffuse corneal edema. A heterozygous missense variant in the KIAA1522 gene (c.1331G>A; p.R444Q) was identified by WES, which was present in all 6 patients but was absent in the unaffected members and healthy controls.

CONCLUSIONS

The clinical features of atypical ECD are unique compared with those of known corneal dystrophies. Moreover, genetic analysis identified the c.1331G>A variant in KIAA1522 , which may be responsible for the pathogenesis of this atypical ECD. Thus, we propose this is a new form of ECD based on our clinical findings.

Corneal Regeneration Using Gene Therapy Approaches

One of the most remarkable advancements in medical treatments of corneal diseases in recent decades has been corneal transplantation. However, corneal transplants, including lamellar strategies, have their own set of challenges, such as graft rejection, delayed graft failure, shortage of donor corneas, repeated treatments, and post-surgical complications. Corneal defects and diseases are one of the leading causes of blindness globally; therefore, there is a need for gene-based interventions that may mitigate some of these challenges and help reduce the burden of blindness. Corneas being immune-advantaged, uniquely avascular, and transparent is ideal for gene therapy approaches. Well-established corneal surgical techniques as well as their ease of accessibility for examination and manipulation makes corneas suitable for in vivo and ex vivo gene therapy. In this review, we focus on the most recent advances in the area of corneal regeneration using gene therapy and on the strategies involved in the development of such therapies. We also discuss the challenges and potential of gene therapy for the treatment of corneal diseases. Additionally, we discuss the translational aspects of gene therapy, including different types of vectors, particularly focusing on recombinant AAV that may help advance targeted therapeutics for corneal defects and diseases.

Management of Stromal Corneal Dystrophies; Review of the Literature with a Focus on Phototherapeutic Keratectomy and Keratoplasty

Corneal dystrophies are a group of non-inflammatory inherited disorders of the cornea. This review considers treatment options for epithelial-stromal and stromal corneal dystrophies: namely Reis–Bücklers, Thiel–Behnke, lattice, Avellino, granular, macular and Schnyder corneal dystrophies. Where there is visual reduction, treatment options may include either phototherapeutic keratectomy (PTK) or corneal transplantation. Due to the anterior location of the deposits in Reis-Bücklers and Thiel–Behnke dystrophies, PTK is considered the treatment of choice. For lattice, Avellino, granular and macular corneal dystrophies, PTK provides temporary visual improvement; however, with recurrences, repeat PTK or a corneal transplant would be needed. For Schnyder dystrophy, should treatment be required, PTK may be the preferred option due to the potential for recurrence of the disease in corneal transplantation. This review discusses the literature and evidence base for the treatment of corneal dystrophies in terms of visual outcomes and recurrence rate.

Keratoconus in two siblings with congenital distichiasis

PURPOSE

To describe a previously unreported association of keratoconus in congenital distichiasis.

METHODS

Observational case series of ocular findings in 2 siblings with congenital distichiasis.

RESULTS

A 17-year-old male presented with tearing and photophobia in both eyes. His parents revealed that he was photophobic since birth. He had a lid surgery previously in both eyes. Clinical examination revealed a central scar with Descemet membrane tear suggestive of healed hydrops in the right eye. The left eye showed topographic features of keratoconus. His younger sibling, a 14-year-old female, also had similar symptoms of photophobia and tearing since birth. She had undergone electrolysis in both eyes. At the present visit, she had an epithelial defect with congestion in the right eye. Electrolysis of the distichiatic eyelashes was performed along with bandage contact lens application, which relieved her symptoms. Her topography revealed subclinical keratoconus in both eyes. The siblings' father also had complaints of photophobia since birth and had lid surgery and electrolysis in the second decade of his life.

CONCLUSIONS

Patients with congenital distichiasis may have associated keratoconus. Chronic ocular irritation and subsequent eye rubbing in distichiasis could be the risk factor for keratoconus.

Variant Landscape of 15 Genes Involved in Corneal Dystrophies: Report of 30 Families and Comprehensive Analysis of the Literature

Corneal dystrophies (CDs) represent a group of inherited diseases characterized by the progressive deposit of abnormal materials in the cornea. This study aimed to describe the variant landscape of 15 genes responsible for CDs based on a cohort of Chinese families and a comparative analysis of literature reports. Families with CDs were recruited from our eye clinic. Their genomic DNA was analyzed using exome sequencing. The detected variants were filtered using multi-step bioinformatics and confirmed using Sanger sequencing. Previously reported variants in the literature were summarized and evaluated based on the gnomAD database and in-house exome data. In 30 of 37 families with CDs, 17 pathogenic or likely pathogenic variants were detected in 4 of the 15 genes, including TGFBI, CHST6, SLC4A11, and ZEB1. A comparative analysis of large datasets revealed that 12 of the 586 reported variants are unlikely causative of CDs in monogenic mode, accounting for 61 of 2933 families in the literature. Of the 15 genes, the gene most frequently implicated in CDs was TGFBI (1823/2902, 62.82% of families), followed by CHST6 (483/2902, 16.64%) and SLC4A11 (201/2902, 6.93%). This study presents, for the first time, the landscape of pathogenic and likely pathogenic variants in the 15 genes responsible for CDs. Awareness of frequently misinterpreted variants, such as c.1501C>A, p.(Pro501Thr) in TGFBI, is crucial in the era of genomic medicine.