Real-world clinical and molecular management of 50 prospective patients with microphthalmia, anophthalmia and/or ocular coloboma

BACKGROUND/AIMS

Microphthalmia, anophthalmia and coloboma (MAC) are clinically and genetically heterogenous rare developmental eye conditions, which contribute to a significant proportion of childhood blindness worldwide. Clear understanding of MAC aetiology and comorbidities is essential to providing patients with appropriate care. However, current management is unstandardised and molecular diagnostic rates remain low, particularly in those with unilateral presentation. To further understanding of clinical and genetic management of patients with MAC, we charted their real-world experience to ascertain optimal management pathways and yield from molecular analysis.

METHODS

A prospective cohort study of consecutive patients with MAC referred to the ocular genetics service at Moorfields Eye Hospital between 2017-2020.

RESULTS

Clinical analysis of 50 MAC patients (15 microphthalmia; 2 anophthalmia; 11 coloboma; and 22 mixed) from 44 unrelated families found 44% had additional ocular features (complex) and 34% had systemic involvement, most frequently intellectual/developmental delay (8/17). Molecular analysis of 39 families using targeted gene panels, whole genome sequencing and microarray comparative genomic hybridisation identified genetic causes in, 28% including novel variants in six known MAC genes (SOX2, KMT2D, MAB21L2, ALDH1A3, BCOR and FOXE3), and a molecular diagnostic rate of 33% for both bilateral and unilateral cohorts. New phenotypic associations were found for FOXE3 (bilateral sensorineural hearing loss) and MAB21L2 (unilateral microphthalmia).

CONCLUSION

This study highlights the importance of thorough clinical and molecular phenotyping of MAC patients to provide appropriate multidisciplinary care. Routine genetic testing for both unilateral and bilateral cases in the clinic may increase diagnostic rates in the future, helping elucidate genotype-phenotype correlations and informing genetic counselling.

Normal and abnormal foveal development

Normal foveal development begins in utero at midgestation with centrifugal displacement of inner retinal layers (IRLs) from the location of the incipient fovea. The outer retinal changes such as increase in cone cell bodies, cone elongation and packing mainly occur after birth and continue until 13 years of age. The maturity of the fovea can be assessed invivo using optical coherence tomography, which in normal development would show a well-developed foveal pit, extrusion of IRLs, thickened outer nuclear layer and long outer segments. Developmental abnormalities of various degrees can result in foveal hypoplasia (FH). This is a characteristic feature for example in albinism, aniridia, prematurity, foveal hypoplasia with optic nerve decussation defects with or without anterior segment dysgenesis without albinism (FHONDA) and optic nerve hypoplasia. In achromatopsia, there is disruption of the outer retinal layers with atypical FH. Similarly, in retinal dystrophies, there is abnormal lamination of the IRLs sometimes with persistent IRLs. Morphology of FH provides clues to diagnoses, and grading correlates to visual acuity. The outer segment thickness is a surrogate marker for cone density and in foveal hypoplasia this correlates strongly with visual acuity. In preverbal children grading FH can help predict future visual acuity.

Clinical spectrum of non-syndromic microphthalmos, anophthalmos and coloboma in the paediatric population: a multicentric study from North India

AIMS

To describe the clinical features, visual acuity and causes of ocular morbidity in children (0-18 years) with microphthalmos, anophthalmos, and coloboma (MAC) from North India.

METHODS

A retrospective study conducted between October 2017 and September 2018 in three tertiary eye institutes, part of the Bodhya Eye Consortium with consensus led common pro formas. Children with complete clinical data and without syndromic/systemic involvement were included. The clinical phenotype was divided into isolated ocular coloboma (CB), coloboma with microcornea (CBMC), colobomatous microphthalmos (CBMO), non-colobomatous microphthalmos (MO) and anophthalmos (AO).

RESULTS

A total of 532 children with MAC were examined. Seventeen records were excluded due to incomplete data (0.2%). 515 children (845 eyes) were included: 54.4% males and 45.6% females. MAC was unilateral in 36% and bilateral in 64%. CB, CBMC, CBMO, MO and AO were seen in 26.4%, 31%, 22%, 8% and 12.5% of eyes, respectively. Nystagmus was found in 40%, strabismus in 23%, cataract in 18.7% and retinal detachment in 15%. Best-corrected visual acuity (BCVA) of <3/60 was seen in 62.4% eyes. Blindness (BCVA <3/60 in better eye) was seen in 42.8% of bilateral patients. Those with microcornea or microphthalmos with coloboma had worse BCVA (p<0.001). There were regional differences in the type of MAC phenotype presenting to the three institutes.

CONCLUSION

The MAC group of disorders cause significant ocular morbidity. The presence of microcornea or microphthalmos with coloboma predicts worse BCVA. The variation of the MAC phenotype with the district of origin of the patient raises questions of aetiology and is subject to further studies.

Thinner retinal nerve fibre layer in young adults with foetal alcohol spectrum disorders

BACKGROUND/AIMS

Ophthalmological abnormalities such as ptosis, strabismus, refractive errors and optic nerve hypoplasia have been reported in foetal alcohol spectrum disorders (FASD). The purpose of this study was to investigate whether retinal thickness, retinal nerve fibre layer (RNFL) and optic disc area (ODA) differ between individuals with FASD and healthy controls.

METHODS

Best-corrected visual acuity (BCVA) in terms of logarithm of the minimum angle of resolution (logMAR), refraction, and fundus variables measured by optical coherence tomography were obtained from 26 young adults with FASD (12 women, median age 23 years) and 27 controls (18 women, median age 25 years).

RESULTS

The total thickness of the peripapillary RNFL was significantly lower in the FASD group than in controls; median (range) in the right/left eye was 96.5 (60-109)/96 (59-107) µm in the FASD group and 105 (95-117)/103 (91-120) µm among controls (p=0.001 and p=0.0001). Macular RNFL and retinal thickness measurements from the FASD group were also lower in most of the nine ETDRS areas, except for the central parts. Median (range) BCVA in the best eye was 0.00 (-0.1-0.3) logMAR in the FASD group and 0.00 (-0.2-0.0) logMAR in controls (p=0.001). No significant differences between the groups were found regarding ODA or refraction.

CONCLUSION

Significant differences in peripapillary and macular RNFL, retinal thickness and BCVA were found in this group of young adults with FASD compared with healthy controls. However, there were no differences in the size of the optic disc.

Optical coherence tomography angiography of foveal hypoplasia

AIMS

To discuss foveal development in the context of detailed retinal vasculature imaging in foveal hypoplasia using optical coherence tomography angiography.

METHODS

In this case series, the optical coherence tomography angiography results of four patients with idiopathic foveal hypoplasia and two patients with foveal hypoplasia secondary to oculocutaneous albinism are presented.

RESULTS

Cases with intact visual acuity demonstrated lower grades of foveal hypoplasia on optical coherence tomography, while those with poor vision demonstrated high grades of foveal hypoplasia. The superficial retinal capillary plexus was intact in the foveal area in all cases, with no demonstrable foveal avascular zone. The deep retinal capillary plexus was absent to variable degrees in most cases, but was most persistent in those cases with reduced vision.

CONCLUSIONS

The superficial retinal capillary plexus is present in cases with foveal hypoplasia, while the deep retinal capillary plexus is absent to varying degrees. Our findings support the hypothesis that an intact foveal avascular zone of the deep capillary plexus allows for outer retinal photoreceptor specialisation to occur unimpeded, resulting in preserved visual acuity, while this process may be inhibited by an absent deep capillary foveal avascular zone with resultant poor vision.

Trends over time in the incidence of congenital anophthalmia, microphthalmia and orbital malformation in England: database study

AIMS

To study trends over time in the incidence of congenital anophthalmia, microphthalmia and orbital malformations in England, along with changes in hospital admission rates for these conditions.

METHODS

Using English National Hospital Episode Statistics (1999-2011), the annual rate of hospital admissions related to anophthalmia, microphthalmia and congenital malformations of orbit/lacrimal apparatus was calculated per 100 000 infants. The records were person-linked, which enabled patients' 'first record' rates to be calculated as proxies for incidence. Similar analyses on pre-1999 datasets were also undertaken for microphthalmia.

RESULTS

There was no systematic increase or decrease over time in the incidence of these conditions, but there was some fluctuation from year to year. The incidence of congenital anophthalmia ranged from 2.4 (95% CI 1.3 to 4.0) per 100 000 infants in 1999 to 0.4 (0 to 1.3) in 2011. The annual incidence of congenital microphthalmia was 10.8 (8.2 to 13.5) in 1999 and 10.0 (7.6 to 12.4) in 2011. The annual incidence of congenital orbital/lacrimal malformations was 0.5 (0 to 1.1) in 1999 and 0.7 (0 to 1.4) in 2011. Including multiple admissions per person, admission rates for microphthalmia showed a linear increase over time from 1999. The earlier data for microphthalmia indicated an increase in admission rates, but no change in incidence, from 1971 to 2011.

CONCLUSIONS

The incidence of these conditions has remained stable in England in recent years. Although the incidence of microphthalmia was stable, hospital admission rates for it increased over time reflecting an increase in multiple admissions per affected person. These data may be useful for planning service provision.

Familial acorea, microphthalmia and cataract syndrome

PURPOSE

To describe the clinical features of members of a family with acorea, microphthalmia and cataract syndrome. In addition, to perform linkage analysis on family members to determine possible candidate genes.

METHODS

Comprehensive ophthalmic examinations were performed on five affected members of a family consisting of a paternal grandmother, father and three children. In addition, DNA was extracted from nine family members (the five affected and four normal members) and used for genome-wide single nucleotide polymorphism genotyping and linkage analysis.

RESULTS

All of the affected patients had acorea or fibrous occlusion of the pupil, microphthalmia and cataracts in both eyes. They also had microcornea and iridocorneal dysgenesis. Examination of the crystalline lens was hindered by the abnormal iris surface, but cataracts were detected by ultrasound biomicroscopy. Surgical reconstruction of the pupil allowed a better view of the posterior pole of the eye, and ophthalmoscopy showed a normal retina and optic disc. No systemic abnormalities were observed. Linkage analysis did not reach significance but narrowed the location of possible candidate genes to chromosomes 1, 5, 8, 11 and 17.

CONCLUSIONS

This acorea, microphthalmia and cataract syndrome has not previously been reported. Genetic analyses indicate that this syndrome is probably due to an autosomal dominant mutation.