Classification of posterior polymorphous corneal dystrophy as a corneal ectatic disorder following confirmation of associated significant corneal steepening

Poor intraoperative visibility and postoperative astigmatism associated with trabecular micro-bypass stent for corneal dystrophy: A case report

RATIONALE

There are reports of safe cataract surgery in eyes with posterior polymorphous corneal dystrophy (PPCD); however, to our knowledge, there are no reports of minimally invasive glaucoma surgery (MIGS) in eyes with PPCD. Herein, we report a case of poor intraoperative visibility with gonioscopy, postoperative corneal edema, and corneal astigmatism in eyes with PPCD treated with trabecular micro-bypass stent combined with cataract surgery.

PATIENT CONCERNS/DIAGNOSIS

A 78-year-old man was referred to our hospital for MIGS. He presented with bilateral corneal endothelial vesicular changes and band lesions. Endothelial cell density was 2983/2871 cells/mm2 (right/left eye), central corneal thickness was 581 μm/572 μm, best-corrected visual acuity values (Snellen equivalent) were 20/32 (right) and 20/100 (left), and corneal astigmatism was -2.7D in the right eye and -2.5D in the left eye.

INTERVENSIONS/ OUTCOMS

After phacoemulsification and aspiration with intraocular lens implantation with a 2.4-mm corneal incision in both eyes, trabecular micro-bypass stents were inserted successfully despite the poor intraoperative visibility with gonioscopy. One week after surgery, the central corneal thickness was 614 μm/609 μm, and Descemet's membrane folds and mild corneal edema were observed. Best-corrected decimal visual acuity was 20/40 for the right eye and 20/50 for the left eye. In the left eye, total corneal astigmatism increased from -2.5D to -5.5D. Corneal astigmatism and edema showed gradual improvement.

LESSONS

Although reports have shown that cataract surgery can be safely performed in eyes with PPCD, MIGS in eyes with PPCD may require caution regarding intraoperative visibility with gonioscopy and visual function in the early postoperative period.

Posterior Polymorphous Corneal Dystrophy in a Patient with a Novel ZEB1 Gene Mutation

Posterior polymorphous corneal dystrophy (PPCD), a rare, bilateral, autosomal-dominant, inherited corneal dystrophy, affects the Descemet membrane and corneal endothelium. We describe an unusual presentation of PPCD associated with a previously unknown genetic alteration in the ZEB1 gene. The proband is a 64-year-old woman diagnosed with keratoconus referred for a corneal endothelium study who presented endothelial lesions in both eyes suggestive of PPCD, corectopia and iridocorneal endothelial synechiae in the right eye and intrastromal segments in the left eye. The endothelial count was 825 in the right eye and 1361 in the left eye, with typical PPCD lesions visible under specular and confocal microscopy. In the next generation sequencing genetic analysis, a heterozygous c.1A > C (p.Met1Leu) mutation was found in the ZEB1 gene (TCF8). The PPCD3 subtype is associated with corneal ectasia, and both can appear due to a pathogenic mutation in the ZEB1 gene (OMIM #189909). However, our patient had a previously unreported mutation in the ZEB1 gene, which mediates the transition between cell lines and provides a pathogenic explanation for the epithelialisation of the corneal endothelium, a characteristic of PPCD.

Update on the genetics of corneal endothelial dystrophies

Corneal endothelial dystrophies are a heterogeneous group of diseases with different modes of inheritance and genetic basis for each dystrophy. The genes associated with these diseases encode transcription factors, structural components of the stroma and Descemet membrane, cell transport proteins, and others. Congenital hereditary endothelial dystrophy (CHED) is associated with mutations in two genes, OVOL2 and SLC4A11, for dominant and recessive forms of CHED, respectively. Mutations in three genes are known to cause posterior polymorphous corneal dystrophy (PPCD). They are OVOL2 (PPCD1), ZEB1 (PPCD3), and GRHL1 (PPCD4). The PPCD2 locus involving the collagen gene COL8A2 on chromosome 1 is disputed due to insufficient evidence. Mutations in the COL8A2 gene are associated with early-onset Fuchs’ endothelial corneal dystrophy (FECD). Several genes have been associated with the more common, late-onset FECD. Alterations in each of these genes occur in a fraction of patients, and the most prevalent genetic alteration in FECD patients across the world is a triplet repeat expansion in the TCF4 gene. Knowledge of the genetics of corneal endothelial dystrophies has considerably advanced within the last decade and has contributed to better diagnosis of these dystrophies as well as opened up the possibility of novel therapeutic approaches based on the molecular mechanisms involved. The functions of genes identified to date provide insights into the pathogenic mechanisms involved in each disorder.

Posterior corneal vesicles are not associated with the genetic variants that cause posterior polymorphous corneal dystrophy

PURPOSE

Posterior corneal vesicles (PCVs) have clinical features that are similar to posterior polymorphous corneal dystrophy (PPCD). To help determine whether there is a shared genetic basis, we screened 38 individuals with PCVs for changes in the three genes identified as causative for PPCD.

METHODS

We prospectively recruited patients for this study. We examined all individuals clinically, with their first-degree relatives when available. We used a combination of Sanger and exome sequencing to screen regulatory regions of OVOL2 and GRHL2, and the entire ZEB1 coding sequence.

RESULTS

The median age at examination was 37.5 years (range 4.7-84.0 years), 20 (53%) were male and in 19 (50%) the PCVs were unilateral. Most individuals were discharged to optometric review, but five had follow-up for a median of 12 years (range 5-13 years) with no evidence of progression. In cases with unilateral PCVs, there was statistically significant evidence that the change in the affected eye was associated with a lower endothelial cell density (p = 0.0003), greater central corneal thickness (p = 0.0277) and a steeper mean keratometry (p = 0.0034), but not with a higher keratometric astigmatism or a reduced LogMAR visual acuity. First-degree relatives of 13 individuals were available for examination, and in 3 (23%), PCVs were identified. No possibly pathogenic variants were identified in the PPCD-associated genes screened.

CONCLUSION

We found no evidence that PCVs share the same genetic background as PPCD. In contrast to PPCD, we confirm that PCVs is a mild, non-progressive condition with no requirement for long-term review. However, subsequent cataract surgery can lead to corneal oedema.

Posterior Polymorphous Corneal Dystrophy in a Pediatric Population

PURPOSE

The aim of this study was to evaluate the clinical and topographic features of posterior polymorphous corneal dystrophy (PPCD) in children aged 15 years or younger with a long-term follow-up. Retrospective case series.

METHODS

A retrospective chart review of patients who were diagnosed with PPCD at Boston Children's Hospital from 1999 to 2020 was performed. Data collected included age at the time of diagnosis, slit lamp findings, cycloplegic refraction, best-corrected visual acuity, central corneal thickness, specular microscopy, and corneal topography findings whenever available.

RESULTS

Twenty-seven eyes of 19 patients were included (11 unilateral and 8 bilateral cases). Ten patients were girls (52.6%). Left eye was affected in 14 eyes. The mean age at the time of diagnosis was 8.5 ± 3.3 years, with a mean follow-up of 5.3 years. In unilateral cases, there was a statistically significant difference in the endothelial cell density (P = 0.01), coefficient variation (P = 0.03), and hexagonality (P = 0.01) between the affected and the contralateral unaffected eyes. The mean best-corrected visual acuity at initial presentation was 0.8 ± 0.2 compared with 0.9 ± 0.08 in unaffected eyes (P = 0.04). The mean astigmatism was higher in the affected eye (+1.7 diopters) compared with (+1.00) the unaffected eye (P = 0.07). At initial presentation, 7 of 27 eyes had amblyopia, which resolved, either partially or completely, in 5 eyes after treatment.

CONCLUSIONS

PPCD can present early in children with astigmatism and anisometropic amblyopia. A careful slit lamp examination for children presenting with anisoastigmatism is necessary to diagnose PPCD. Contrary to adults, presentation is often unilateral. Such patients should be followed up regularly with cycloplegic retinoscopy to prevent and treat refractive amblyopia if present.

Clearing the Haze: Navigating Corneal Refractive Surgery in Patients with Posterior Polymorphous Corneal Dystrophy

Posterior polymorphous corneal dystrophy (PPCD) is a corneal disorder of the endothelium and Descemet’s membrane. Although reports of corneal refractive surgery including laser-assisted in situ keratomileusis (LASIK), photorefractive keratectomy (PRK), and small incision lenticule extraction (SMILE) in PPCD are minimal, these procedures have been shown to be safe and effective in this patient population. Proceeding with corneal refractive surgery in eyes with PPCD raises concerns regarding corneal integrity, including long-term biomechanical instability, risk of ectasia, endothelial cell loss, disease progression, and corneal decompensation. Thus, LASIK, PRK, and SMILE should be considered with caution. This commentary explores the patient characteristics associated with favorable surgical outcomes and factors that weigh against proceeding with refractive surgery.

Expression and Function of ZEB1 in the Cornea

ZEB1 is an important transcription factor for epithelial to mesenchymal transition (EMT) and in the regulation of cell differentiation and transformation. In the cornea, ZEB1 presents in all three layers: the epithelium, the stroma and the endothelium. Mutations of ZEB1 have been linked to multiple corneal genetic defects, particularly to the corneal dystrophies including keratoconus (KD), Fuchs endothelial corneal dystrophy (FECD), and posterior polymorphous corneal dystrophy (PPCD). Accumulating evidence indicates that dysfunction of ZEB1 may affect corneal stem cell homeostasis, and cause corneal cell apoptosis, stromal fibrosis, angiogenesis, squamous metaplasia. Understanding how ZEB1 regulates the initiation and progression of these disorders will help us in targeting ZEB1 for potential avenues to generate therapeutics to treat various ZEB1-related disorders.

CLEAR - Medical use of contact lenses

The medical use of contact lenses is a solution for many complex ocular conditions, including high refractive error, irregular astigmatism, primary and secondary corneal ectasia, disfiguring disease, and ocular surface disease. The development of highly oxygen permeable soft and rigid materials has extended the suitability of contact lenses for such applications. There is consistent evidence that bandage soft contact lenses, particularly silicone hydrogel lenses, improve epithelial healing and reduce pain in persistent epithelial defects, after trauma or surgery, and in corneal dystrophies. Drug delivery applications of contact lens hold promise for improving topical therapy. Modern scleral lens practice has achieved great success for both visual rehabilitation and therapeutic applications, including those requiring retention of a tear reservoir or protection from an adverse environment. This report offers a practical and relevant summary of the current evidence for the medical use of contact lenses for all eye care professionals including optometrists, ophthalmologists, opticians, and orthoptists. Topics covered include indications for use in both acute and chronic conditions, lens selection, patient selection, wear and care regimens, and recommended aftercare schedules. Prevention, presentation, and management of complications of medical use are reviewed.

Keratoconus in a patient with Alport syndrome: A case report

BACKGROUND

Known ocular manifestations of Alport syndrome include features such as anterior lenticonus and fleck retinopathy. Reports of keratoconus in such patients are limited. We report tomographic findings consistent with keratoconus in a patient with Alport syndrome.

CASE SUMMARY

A 52-year-old female was referred to our ophthalmology clinic with decreased vision and increased tearing. She was diagnosed with stage III Alport syndrome two years prior. Upon examination she was found to have average keratometries of 48 D bilaterally with tomographic evidence of keratoconus.

CONCLUSION

Although a rare presentation, concurrent Alport syndrome and keratoconus should be considered when reviewing the ocular health of Alport syndrome patients and appropriate management steps should be taken upon the diagnosis.

Corneal Perforation After Corneal Cross-Linking in Keratoconus Associated With Potentially Pathogenic ZNF469 Mutations

PURPOSE

To report a case of bilateral and repetitive corneal perforations after corneal cross-linking (CXL) for keratoconus in a woman harboring potentially pathogenic variants in the ZNF469 gene and to characterize the keratoconus phenotype in this woman and her daughter who shared the same ZNF469 mutations.

METHODS

Clinical characterization of the proband and her daughter followed by sequencing of the genes associated with brittle cornea syndrome, ZNF469 and PRDM5, in both individuals.

RESULTS

An Ashkenazi Jewish woman in her sixth decade presented with diffuse corneal thinning and progressive steepening consistent with keratoconus. After CXL, epithelium-off in the first eye and epithelium-on in the second, she developed spontaneous corneal perforations in each eye. Her daughter in her fourth decade demonstrated a similar pattern of diffuse corneal thinning and progressive corneal steepening but did not undergo CXL and did not develop corneal perforation. Screening of the ZNF469 and PRDM5 genes revealed 3 missense ZNF469 variants (c.2035G>A, c.10244G>C, and c.11119A>G) in cis arrangement on 1 allele of ZNF469 in both proband and her daughter. Although the 3 variants share low (<0.01) global minor allele frequencies, each has significantly higher minor allele frequencies (0.01-0.03) in the Ashkenazi Jewish population, leading to uncertainty regarding a pathogenic role for the identified variants.

CONCLUSIONS

CXL may be associated with the development of corneal perforation in particular at-risk individuals with keratoconus. Identifying clinical and genetic risk factors, including screening of ZNF469 and PRDM5, may be useful in the prevention of significant complications after CXL.

Fuchs endothelial corneal dystrophy and corneal endothelial diseases: East meets West

Fuchs endothelial corneal dystrophy (FECD) is amongst one of the most common indications for endothelial keratoplasty worldwide. Despite being originally described among Caucasians, it is now known to be prevalent among a large number of populations, including Asians. While the FECD phenotype is classically described as that of central guttate and pigment deposits associated with corneal endothelial dysfunction, there are subtle yet important differences in how FECD and its phenocopies may present in Caucasians vs Asians. Such differences are paralled by genotypic variations and disease management preferences which appear to be geographically and ethnically delineated. This article provides a succinct review of such differences, with a focus on diagnostic and management issues which may be encountered by ophthalmologists practicing in the different geographic regions, when evaluating a patient with FECD.

CUGC for posterior polymorphous corneal dystrophy (PPCD)

Name of the disease (synonyms) CUGC for posterior polymorphous corneal dystrophy (PPCD).OMIM# of the disease 122000; 609141; 618031.Name of the analysed genes or DNA/chromosome segments OVOL2 (PPCD1); ZEB1 (PPCD3); GRHL2 (PPCD4).OMIM# of the gene(s) 616441; 189909; 608576. Review of the analytical and clinical validity as well as of the clinical utility of DNA-based testing for variants in theOVOL2, ZEB1andGRHL2gene(s) in a diagnostic setting, predictive and parental settings and for risk assesment in relatives.

Alport Patients without Classic Ocular Symptoms Have Smaller Lens Diameter

Background

The aim of this study was to present ophthalmological findings regarding Alport syndrome and report refractometry data and to present possible early signs of the syndrome.

Material/Methods

Seven patients suffering from Alport syndrome were referred to the Department of Ophthalmology at the University of Debrecen between January 1^st, 2014, and December 31^st, 2015. All patients underwent slit lamp evaluation and dilated fundus biomicroscopy, with special attention paid to lenticonus and retinal changes. IOL Master, Pentacam HR, and ultrasound biomicroscopy were performed to assess keratometry, corneal thickness, anterior chamber depth, lens size, and axial length data.

Results

One patient out of seven had ocular symptoms. Posterior polymorphous corneal dystrophy (PPMD) and dot-and-fleck retinopathy were seen. Meanwhile, although keratoconus was not proven, remarkable astigmatism with high myopia was detected. The other six patients were found to have a significantly smaller lens diameter (an average of 7.82±0.66 mm, p=0.035) compared to normal controls (an average of 8.65±0.46 mm). Lenses also tended to be thicker in Alport patients (3.48±0.19 mm) compared to controls (3.4±0.2 mm), although the difference was not significant (p=0.394). The power of the lens also showed a significant difference (p=0.026), with Alport patients having lower lens power.

Conclusions

Alport syndrome patients without classical ophthalmological findings have smaller crystalline lens diameter and lower lens power. These signs may support the diagnosis of Alport syndrome. Ophthalmologists should not only seek for the known classic signs, but also the parameters of the crystalline lens, especially if genetic testing is not available.

Corneal endothelial cell dysfunction: etiologies and management

A transparent cornea is essential for the formation of a clear image on the retina. The human cornea is arranged into well-organized layers, and each layer plays a significant role in maintaining the transparency and viability of the tissue. The endothelium has both barrier and pump functions, which are important for the maintenance of corneal clarity. Many etiologies, including Fuchs’ endothelial corneal dystrophy, surgical trauma, and congenital hereditary endothelial dystrophy, lead to endothelial cell dysfunction. The main treatment for corneal decompensation is replacement of the abnormal corneal layers with normal donor tissue. Nowadays, the trend is to perform selective endothelial keratoplasty, including Descemet stripping automated endothelial keratoplasty and Descemet’s membrane endothelial keratoplasty, to manage corneal endothelial dysfunction. This selective approach has several advantages over penetrating keratoplasty, including rapid recovery of visual acuity, less likelihood of graft rejection, and better patient satisfaction. However, the global limitation in the supply of donor corneas is becoming an increasing challenge, necessitating alternatives to reduce this demand. Consequently, in vitro expansion of human corneal endothelial cells is evolving as a sustainable choice. This method is intended to prepare corneal endothelial cells in vitro that can be transferred to the eye. Herein, we describe the etiologies and manifestations of human corneal endothelial cell dysfunction. We also summarize the available options for as well as recent developments in the management of corneal endothelial dysfunction.

Effect of Posterior Corneal Vesicles on Corneal Endothelial Cell Density and Anisometropic Amblyopia

PURPOSE

To evaluate the effect of corneal vesicles in patients with posterior corneal vesicles (PCV) on corneal endothelial cell (CEC) density and the acquisition of amblyopia.

METHODS

In this retrospective study of patients with PCV (18 eyes of 14 patients), CEC density was examined by noncontact specular microscopy during each follow-up examination. Best-corrected visual acuity and the objective refractive error were also examined.

RESULTS

Of the 14 total patients, 10 were diagnosed with PCV and 4 were diagnosed with bilateral suspected PCV or posterior polymorphous corneal dystrophy (PPCD), and in all patients, no ocular abnormality other than corneal vesicles was observed. In patients with PCV and patients with bilateral suspected PCV or PPCD, mean CEC density was 1131 ± 338 and 1095 ± 492 cells/mm, respectively. In both PCV group and the bilateral suspected PCV or PPCD-group patients who were followed for 164.2 ± 25.4 months (range: 123-186 months), CEC density tended not to decrease. In patients with PCV, the mean best-corrected visual acuity of the unaffected eyes was significantly higher than that of the affected eyes with corneal vesicles (-0.10 ± 0.06 and 0.05 ± 0.13, respectively, P = 0.012). Four of 9 affected eyes (1 eye was excluded because of retinal atrophy) exhibited amblyopia, and all 4 eyes had astigmatism higher than 2 diopters.

CONCLUSIONS

Although CEC density of patients with PCV in this study was found to be stable over a long-term follow-up period, strict attention should be given to the possibility of amblyopia in eyes with PCV.

Elucidating the molecular basis of PPCD: Effects of decreased ZEB1 expression on corneal endothelial cell function

PURPOSE

To investigate the functional role that the zinc e-box binding homeobox 1 (ZEB1) gene, which underlies the genetic basis of posterior polymorphous corneal dystrophy 3 (PPCD3), plays in corneal endothelial cell proliferation, apoptosis, migration, and barrier function.

METHODS

A human corneal endothelial cell line (HCEnC-21T) was transfected with siRNA targeting ZEB1 mRNA. Cell proliferation, apoptosis, migration, and barrier assays were performed: Cell proliferation was assessed with cell counting using a hemocytometer; cell apoptosis, induced by either ultraviolet C (UVC) radiation or doxorubicin treatment, was quantified by measuring cleaved caspase 3 (cCASP3) protein levels; and cell migration and barrier function were monitored with electric cell-substrate impedance sensing (ECIS).

RESULTS

ZEB1 knockdown in HCEnC-21T cells transfected with siRNA targeting ZEB1 did not result in a significant difference in cell proliferation when compared with control. Although knockdown of ZEB1 in HCEnC-21T cells sensitized the cells to UV-induced apoptosis, ZEB1 knockdown did not alter the cells' susceptibility to doxorubicin-induced apoptosis, as measured with cCASP3 protein levels, compared with controls. Similarly, no difference was observed in cell migration following ZEB1 knockdown. However, cell barrier function increased significantly following ZEB1 knockdown.

CONCLUSIONS

The corneal endothelium in PPCD3 is characterized by morphologic, anatomic, and molecular features that are more consistent with an epithelial-like rather than an endothelial-like phenotype. Although these characteristics have been well documented, we demonstrate for the first time that susceptibility to UV-induced apoptosis and cell barrier function are significantly altered in the setting of reduced ZEB1. The significance of an altered cellular response to apoptotic stimuli and increased cell barrier function in the pathobiology of PPCD remains to be fully elucidated.

Retinal pathology in the PPCD1 mouse

Retinal phenotypes of the PPCD1 mouse, a mouse model of posterior polymorphous corneal dystrophy, have been characterized. PPCD1 mice on the DBA/2J background (D2.Ppcd1) have previously been reported to develop an enlarged anterior chamber due to epithelialization and proliferation of the corneal endothelium and subsequent blockage of the iridocorneal angle. Results presented here show that D2.Ppcd1 mice develop increased intraocular pressure (IOP), with measurements at three months of age revealing significant increases in IOP. Significant retinal ganglion cell layer cell loss is observed at five months of age. D2.Ppcd1 animals also exhibit marked degeneration of the outer nuclear layer in association with hyperplasia of the retinal pigment epithelium. Evidence of retinal detachment is present as early as three weeks of age. By 3.5 months of age, focal areas of outer nuclear layer loss are observed. Although the Gpnmb^R150X mutation leads to increased IOP and glaucoma in DBA/2J mice, development of anterior segment and retinal defects in D2.Ppcd1 animals does not depend upon presence of the Gpnmb^R150X mutation.

Transcriptomic Profiling of Posterior Polymorphous Corneal Dystrophy

Purpose

To investigate the molecular basis of posterior polymorphous corneal dystrophy (PPCD) by examining the PPCD transcriptome and the effect of decreased ZEB1 expression on corneal endothelial cell (CEnC) gene expression.

Methods

Next-generation RNA sequencing (RNA-seq) analyses of corneal endothelium from two PPCD-affected individuals (one with PPCD3 and one of unknown genetic cause) compared with two age-matched controls, and primary human CEnC (pHCEnC) transfected with siRNA-mediated ZEB1 knockdown. The expression of selected differentially expressed genes was validated by quantitative polymerase chain reaction (qPCR) and/or assessed by in situ hybridization in the corneal endothelium of four independent cases of PPCD (one with PPCD3 and three of unknown genetic cause).

Results

Expression of 16% and 46% of the 104 protein-coding genes specific to ex vivo corneal endothelium was lost in the endothelium of two individuals with PPCD. Thirty-two genes associated with ZEB1 and 3 genes (BMP4, CCND1, ZEB1) associated with OVOL2 were differentially expressed in the same direction in both individuals with PPCD. Immunohistochemistry staining and RNA-seq analyses demonstrated variable expression of type IV collagens in PPCD corneas. Decreasing ZEB1 expression in pHCEnC altered expression of 711 protein-coding genes, many of which are associated with canonical pathways regulating various cellular processes.

Conclusions

Identification of the altered transcriptome in PPCD and in a cell-based model of PPCD provided insight into the molecular alterations characterizing PPCD. Further study of the differentially expressed genes associated with ZEB1 and OVOL2 is expected to identify candidate genes for individuals with PPCD and without a ZEB1 or OVOL2 mutation.

Unilateral Posterior Polymorphous Corneal Dystrophy Presented as Anisometropic Astigmatism: 3 Case Reports

Background

Posterior polymorphous corneal dystrophy (PPCD) is typically considered bilateral and asymptomatic. However, few case reports on patients with unilateral PPCD with asymmetric refractive error have mentioned anisometropic amblyopia development. In support of this, we report 3 cases of unilateral PPCD that presented as anisometropic astigmatism. Visual prognosis related to amblyopia development is discussed.

Case Presentation

All 3 patients had a band lesion in the affected eye and a difference of at least 1.5 diopters in cylindrical refractive error between their eyes. The affected eye had a greater amount of astigmatism in all cases. Two patients (Cases 1 and 2) also had amblyopia in the affected eye. Case 1 was a 25-year-old male with a unilateral PPCD diagnosis and a band lesion involving the visual axis. Case 2 was an 11-year-old boy diagnosed with unilateral PPCD. The boy was treated with occlusion and atropine therapy over a 2-year period. Case 3 was a 4-year-old girl diagnosed with unilateral PPCD. The girl had a 30-month history of corrective spectacle use and had no amblyopia. In all cases, the corneal endothelial cell count was lower in the affected eye than in the unaffected contralateral eye.

Conclusions

Practitioners should closely monitor patients with unilateral PPCD for astigmatic anisometropia and amblyopia development. Visual prognosis for patients with unilateral PPCD may be related to lesion position, age at diagnosis, astigmatism severity, and early-childhood corrective spectacle use.

A unique case of keratoconus with Cogan-Reese syndrome and secondary glaucoma

Keratoconus (KC), though one of the most common corneal degeneration, still continues to be a mystique regarding its pathogenesis, diagnosis, associations, and management; with newer discoveries and evolutions being reported. We report, what we believe to be another new association of KC- Cogan Reese syndrome with secondary glaucoma. A 32-year-old male, diagnosed as bilateral KC, presented for examination. Unilateral Cogan-Reese syndrome and associated secondary glaucoma was identified. These associations had been missed by previous ophthalmologists. The patient was managed with a rigid contact lens for KC and topical antiglaucoma agents for glaucoma. He was advised regular reviews and is under observation till date. We describe the first case known to us of a new association with KC. This case not only highlights the ophthalmologist's need to look for multiple entities linked to KC; but may also pave way for future insights regarding pathogenesis and genetics of these associated diseases.

Thick keratoconic cornea associated with posterior polymorphous corneal dystrophy

INTRODUCTION

We herein report a case of bilateral unusually thick non-edematous keratoconic corneas with associated endothelial features of posterior polymorphous corneal dystrophy (PPCD).

CASE REPORT

We report the case of a 27-year-old myopic woman who presented for refractive surgery. Slit lamp exam showed bilateral corneal protrusion with diffuse deep stromal and endothelial vesicular opacities and small paracentral bands. Topography showed generalized advanced corneal steepening in both eyes with increased anterior and posterior central corneal elevations in comparison to the best fit sphere. Ultrasound pachymetry showed central corneal thickness of 605μm (RE) and 612μm (LE). On specular biomicroscopy, cell density of 2503 cells/mm² RE and 1526 cells/mm² LE with significant cellular pleomorphism and polymegathism were noted.

DISCUSSION

Clinical and paraclinical findings together suggest the presence of simultaneous keratoconus and PPCD. The literature has suggested an association between PPCD and steep cornea. Moreover, many reports have also described cases of associated PPCD and keratoconus with characteristic thinning and ectasia, in comparison to the unusual thick corneas noted in our patient, despite the absence of edema. Identification of genetics factors is further needed to clarify this association.

CONCLUSION

This case describes a patient whose corneas present features of both keratoconus and PPCD and is unique due to the presence of increased corneal thickness despite the absence of edema.

Clinical characterization of posterior polymorphous corneal dystrophy in patients of Indian ethnicity

PURPOSE

To characterize the clinical presentation of posterior polymorphous corneal dystrophy (PPCD) in eyes of Indian ethnicity.

DESIGN

Retrospective cohort study from January 1995 to December 2015.

PARTICIPANTS

Patients with the diagnosis of posterior polymorphous corneal dystrophy.

METHODS

Medical records of the patients were reviewed for clinical presentation. Histology of corneal specimens of those that underwent keratoplasty was assessed.

MAIN OUTCOME MEASURES

Descriptive analysis of clinical condition.

RESULTS

Mean age at first evaluation was 32.5 years (range 1-73 years), male:female = 35:18. Majority (44/53; 83 %) of the patients had bilateral involvement. 5/9 (44 %) patients with unilateral presentation were amblyopic in the affected eye. The clinical features documented were vesicles in 94 eyes, band-like pattern in 32 eyes, edema of varying degree in 23 eyes (12 patients, 1 patient was one eyed), and anterior segment changes in 1 eye. 8/45 (17 %) eyes had a regular astigmatism with steep axis >47 D (range 47.2-56.2 D). 16 eyes of 12 patients who had clinically evident corneal edema underwent keratoplasty. Mean age at keratoplasty was 58 years (range 1-73 years). 8 patients had penetrating keratoplasty (PK) and 8 had Descemet stripping endothelial keratoplasty (DSEK). Mean follow-up after keratoplasty was 4.2 years (1 month to 13 years). Except one, all grafts remained clear till the last follow-up. In all specimens, the Descemet membrane was grossly thickened.

CONCLUSIONS

In our study, 12/53 (22.6 %) patients required keratoplasty for visually significant corneal edema. Except one, all were older adults. The patients who needed keratoplasty were bilaterally afflicted and had visually significant cornea edema in both eyes. With a mean follow-up duration of 4.2 years after keratoplasty, no recurrences were noted.

Identification of Potentially Pathogenic Variants in the Posterior Polymorphous Corneal Dystrophy 1 Locus

Posterior polymorphous corneal dystrophy 1 (PPCD1) is a genetic disorder that affects corneal endothelial cell function and leads to loss of visual acuity. PPCD1 has been linked to a locus on chromosome 20 in multiple families; however, Sanger sequencing of protein-coding genes in the consensus region failed to identify any causative missense mutations. In this study, custom capture probes were utilized for targeted next-generation sequencing of the linked region in a previously reported family with PPCD1. Variants were detected through two bioinformatics pipelines and filtered according to multiple criteria. Additionally, a high-resolution microarray was used to detect copy number variations. No non-synonymous variants in the protein-coding region of annotated genes were identified. However, 12 single nucleotide variants in 10 genes, and 9 indels in 7 genes met the filtering criteria and were considered candidate variants for PPCD1. Eleven single nucleotide variants were confirmed by Sanger sequencing, including 2 synonymous variants and 9 non-coding variants, in 9 genes. One microdeletion was detected in an intron of OVOL2 by microarray but was subsequently not identified by PCR. Using a comprehensive next-generation sequencing approach, a total of 16 genes containing single nucleotide variants or indels that segregated with the affected phenotype in an affected family previously mapped to the PPCD1 locus were identified. Screening of these candidate genes in other families previously mapped to the PPCD1 locus will likely result in the identification of the genetic basis of PPCD1.

Association of a Chromosomal Rearrangement Event with Mouse Posterior Polymorphous Corneal Dystrophy and Alterations in Csrp2bp, Dzank1, and Ovol2 Gene Expression

We have previously described a mouse model of human posterior polymorphous corneal dystrophy (PPCD) and localized the causative mutation to a 6.2 Mbp region of chromosome 2, termed Ppcd1. We now show that the gene rearrangement linked to mouse Ppcd1 is a 3.9 Mbp chromosomal inversion flanked by 81 Kbp and 542 bp deletions. This recombination event leads to deletion of Csrp2bp Exons 8 through 11, Dzank1 Exons 20 and 21, and the pseudogene Znf133. In addition, we identified translocation of novel downstream sequences to positions adjacent to Csrp2bp Exon 7 and Dzank1 Exon 20. Twelve novel fusion transcripts involving Csrp2bp or Dzank1 linked to downstream sequences have been identified. Eight are expressed at detectable levels in PPCD1 but not wildtype eyes. Upregulation of two Csrp2bp fusion transcripts, as well as upregulation of the adjacent gene, Ovol2, was observed. Absence of the PPCD1 phenotype in animals haploinsufficient for Csrp2bp or both Csrp2bp and Dzank1 rules out haploinsufficiency of these genes as a cause of mouse PPCD1. Complementation experiments confirm that PPCD1 embryonic lethality is due to disruption of Csrp2bp expression. The ocular expression pattern of Csrp2bp is consistent with a role for this protein in corneal development and pathogenesis of PPCD1.

Heterozygous deletions at the ZEB1 locus verify haploinsufficiency as the mechanism of disease for posterior polymorphous corneal dystrophy type 3

A substantial proportion of patients with posterior polymorphous corneal dystrophy (PPCD) lack a molecular diagnosis. We evaluated 14 unrelated probands who had a clinical diagnosis of PPCD who were previously determined to be negative for mutations in ZEB1 by direct sequencing. A combination of techniques was used including whole-exome sequencing (WES), single-nucleotide polymorphism (SNP) array copy number variation (CNV) analysis, quantitative real-time PCR, and long-range PCR. Segregation of potentially pathogenic changes with disease was confirmed, where possible, in family members. A putative run of homozygosity on chromosome 10 was identified by WES in a three-generation PPCD family, suggestive of a heterozygous deletion. SNP array genotyping followed by long-range PCR and direct sequencing to define the breakpoints confirmed the presence of a large deletion that encompassed multiple genes, including ZEB1. Identification of a heterozygous deletion spanning ZEB1 prompted us to further investigate potential CNVs at this locus in the remaining probands, leading to detection of two additional heterozygous ZEB1 gene deletions. This study demonstrates that ZEB1 mutations account for a larger proportion of PPCD than previously estimated, and supports the hypothesis that haploinsufficiency of ZEB1 is the underlying molecular mechanism of disease for PPCD3.

Posterior Corneal Steepening in Posterior Polymorphous Corneal Dystrophy

PURPOSE

The aim was to evaluate the anterior and posterior corneal topographic characteristics of three patients with posterior polymorphous corneal dystrophy (PPCD) using a rotating Scheimpflug camera combined with a Placido disc system (Sirius, CSO, Italy).

CASE REPORTS

Two children with unilateral PPCD and a 53-year-old woman with bilateral PPCD were diagnosed by the presence of vesicles and railroad track lesions at the level of the Descemet membrane with slitlamp biomicroscopy and in vivo confocal microscopy. Anisometropic and/or meridional amblyopia was detected in both children. In the 16-year-old child, there was unilateral anterior corneal steepening with high astigmatism (plano -7.00 x 170) in the eye with PPCD. The 5-year-old boy had unilateral axial myopia and against-the-rule corneal astigmatism (-12.00 -2.00 x 90). Corneal topography of the woman revealed with-the-rule astigmatism and thin corneas (464 μm OD and 445 μm OS) in both eyes. Posterior corneal steepening greater than 25 μm either in a vertical or in a horizontal pattern changing with the orientation of the railroad track band lesions was detected in all subjects.

CONCLUSIONS

Besides anterior corneal changes, PPCD seems to cause posterior corneal elevation, which necessitates corneal tomographic evaluation. In unilateral or highly asymmetric cases, children with PPCD should be screened for amblyopia.

A year of cornea in review: 2013

PURPOSE

The goal of this study was to provide an update of significant corneal literature published in 2013.

DESIGN

This study is a systematic literature review.

METHODS

We conducted a systematic review of the English-language literature published from January 1, 2013, to December 31, 2013, using the following PubMed search and Medical Subject Headings terms: cornea transplantation, keratoplasty, Descemet membrane endothelial keratoplasty, Descemet stripping endothelial keratoplasty, cross linking, pre-Descemet's layer, Rho-associated kinase, keratoprosthesis, infectious keratitis, corneal dystrophy, corneal astigmatism, and keratoconus.

RESULTS

This review summarizes relevant and innovative original articles, review articles, and novel techniques from the following journals: American Journal of Ophthalmology, British Journal of Ophthalmology, Cornea, Graefe's Archive for Clinical and Experimental Ophthalmology, Investigative Ophthalmology & Visual Science, JAMA Ophthalmology, Journal of Cataract and Refractive Surgery, Journal of Refractive Surgery, and Ophthalmology. Case reports, abstracts, letters to the Editor, and unpublished work were excluded, as well as articles e-published ahead of print in 2012 that were discussed in the previous review. One hundred twenty-seven articles met the criteria for this review.

CONCLUSIONS

This review summarizes significant cornea-related literature from 2013.

Identification of six novel mutations in ZEB1 and description of the associated phenotypes in patients with posterior polymorphous corneal dystrophy 3

Posterior polymorphous corneal dystrophy 3 (PPCD3) is a rare autosomal dominant disorder caused by mutations in ZEB1. To date all identified disease-causing variants were unique to the studied families, except for c.1576dup. We have detected six novel ZEB1 mutations; c.1749_1750del; p.(Pro584*) and c.1717_1718del; p.(Val573Phefs*12) in two Czech families, c.1176dup; p.(Ala393Serfs*19), c.1100C>A; p.(Ser367*), c.627del; p.(Phe209Leufs*11) in three British families and a splice site mutation, c.685-2A>G, in a patient of Sri Lankan origin. An additional British proband had the c.1576dup; p.(Val526Glyfs*3) mutation previously reported in other populations. Clinical findings were variable and included bilateral congenital corneal opacity in one proband, development of opacity before the age of 2 years in another individual and bilateral iris flocculi in yet another subject. The majority of eyes examined by corneal topography (10 out of 16) had an abnormally steep cornea (flat keratometry 46.5-52.7 diopters, steep keratometry 48.1-54.0 diopters). One proband underwent surgery for cryptorchidism. Our study further demonstrates that PPCD3 can present as corneal edema in early childhood, and that an abnormally steep keratometry is a common feature of this condition. As cryptorchidism has been previously observed in two other PPCD3 cases, its association with the disease warrants further investigation.

Functional impact of ZEB1 mutations associated with posterior polymorphous and Fuchs' endothelial corneal dystrophies

PURPOSE

To assess the impact of zinc finger E-box binding homeobox 1 (ZEB1) gene mutations associated with posterior polymorphous corneal dystrophy 3 (PPCD3) and Fuchs' endothelial corneal dystrophy (FECD).

METHODS

Thirteen of the 27 previously reported ZEB1 truncating mutations associated with PPCD3 and the six previously reported ZEB1 missense mutations associated with FECD were generated and transiently transfected into a corneal endothelial cell line. Protein abundance was determined by immunoblotting, while intracellular localization was determined by fluorescence confocal microscopy.

RESULTS

Three of the 13 ZEB1 truncated mutants, and none of the missense mutants, showed significant decrease in mutant ZEB1 protein levels. Predominant nuclear localization was observed for truncated ZEB1 mutant proteins with a predicted molecular weight of less than 92 kilodaltons. The two largest mutant proteins that lacked a putative nuclear localization signal (NLS), p.(Ser638Cysfs*5) and p.(Gln884Argfs*37), primarily localized to the cytoplasm, while the NLS-containing mutant proteins, p.(Glu997Alafs*7) and p.(Glu1039Glyfs*6), primarily localized to the nucleus. All the missense ZEB1 mutant proteins were exclusively present in the nucleus.

CONCLUSIONS

ZEB1 truncating mutations result in a significant decrease and/or impaired nuclear localization of the encoded protein, indicating that ZEB1 haploinsufficiency in PPCD3 may result from decreased protein production and/or impaired cellular localization. Conversely, as the reported ZEB1 missense mutations do not significantly impact protein abundance or nuclear localization, the effect of these mutations on ZEB1 function and their relationship to FECD, if any, remain to be elucidated.