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

Novel disease-causing variants and phenotypic features of X-linked megalocornea

PURPOSE

The aim of the study was to describe the phenotype and molecular genetic causes of X-linked megalocornea (MGC1). We recruited four British, one New Zealand, one Vietnamese and four Czech families.

METHODS

All probands and three female carriers underwent ocular examination and Sanger sequencing of the CHRDL1 gene. Two of the probands also had magnetic resonance imaging (MRI) of the brain.

RESULTS

We identified nine pathogenic or likely pathogenic and one variant of uncertain significance in CHRDL1, of which eight are novel. Three probands had ocular findings that have not previously been associated with MGC1, namely pigmentary glaucoma, unilateral posterior corneal vesicles, unilateral keratoconus and unilateral Fuchs heterochromic iridocyclitis. The corneal diameters of the three heterozygous carriers were normal, but two had abnormally thin corneas, and one of these was also diagnosed with unilateral keratoconus. Brain MRI identified arachnoid cysts in both probands, one also had a neuroepithelial cyst, while the second had a midsagittal neurodevelopmental abnormality (cavum septum pellucidum et vergae).

CONCLUSION

The study expands the spectrum of pathogenic variants and the ocular and brain abnormalities that have been identified in individuals with MGC1. Reduced corneal thickness may represent a mild phenotypic feature in some heterozygous female carriers of CHRDL1 pathogenic variants.

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.

Endothelial cell density in children with posterior polymorphous corneal dystrophy: a longitudinal case-control study

OBJECTIVE

To evaluate longitudinal endothelial cell characteristics of children with posterior polymorphous corneal dystrophy (PPCD).

METHODS

In this prospective case-control study, children with PPCD were followed with slit-lamp photography and non-contact specular microscopy. Patient's eyes were subdivided according to the clinical subtypes of PPCD (vesicular, band, diffuse, and unaffected) and the number of lesions present on the posterior corneal surface. Findings were then compared with age-matched controls.

RESULTS

Thirty eyes of 15 patients with PPCD with a mean age 10.5 ± 3.1 years were analysed. Mean follow-up was 3.0 ± 1.0 years. PPCD morphology was vesicular in 40%, diffuse in 37%, band type in 10% and 13% had no detectable lesions despite contralateral involvement. Fourteen eyes (47%) had ≥5 endothelial lesions. Patients with PPCD had significantly lower endothelial cell densities (ECD) at recruitment (1918.9 ± 666.3 vs. 3340.1 ± 286.5 cells/mm², p < 0.007) and at final follow-up (1793.1 ± 684.6 vs. 3265.2 ± 304.3 cells/mm², p < 0.007) compared to age-matched controls. The lowest ECDs were found in eyes with diffuse type PPCD and those with ≥5 posterior corneal lesions, while clinically unaffected eyes in patients with confirmed PPCD in fellow eye had a normal ECD. However, the rates of annual ECD decline were not significantly different between eyes with PPCD in general, between the subgroups of PPCD and the normative groups.

CONCLUSION

Endothelial cell density is significantly reduced among children with PPCD and depends on the clinical subtype and the number of posterior corneal lesions present. However, annual ECD loss is similar between normal eyes and those with PPCD.