Genetics and ocular disorders: a focused review

Prevalence of Congenital Ocular Anomalies in 15 Countries of Europe: Results From the Medikeye Study

BACKGROUND

Congenital ocular anomalies (COA) are among the most common causes of visual impairment in children in high-income countries. The aim of the study is to describe the prevalence of the various COA recorded in European population-based registries of CA (EUROCAT) participating in the EUROmediCAT consortium.

METHODS

Data from 19 EUROmediCAT registries and one healthcare database (EFEMERIS) were included in this descriptive epidemiological study. Cases of COA included live births, FD from 20 weeks gestational age (GA), and termination of pregnancy for fetal anomaly.

RESULTS

The prevalence of total COA was 3.47/10,000 births (95% CI [3.61-3.82]), ranging from 1.41 to 13.46/10,000 depending on the registry. Among COA cases, congenital lens anomalies were the most frequent anomalies (31%), of which over half were single ocular anomalies (presenting with only one ocular anomaly). An/microphthalmia was the second most frequent COA (24%) of which three-quarters were multiply malformed (associated to extraocular major anomalies). Among single COA cases, 58 were prenatally diagnosed (4%), of which, 58% were diagnosed in the second trimester. Known genetic causes of COA explained 2.5%-25% of COA depending on their class.

CONCLUSIONS

This is the first European study describing COA. The detailed prevalence data offered in this study could improve screening and early diagnosis of different classes of COA. As COA are rare, epidemiological surveillance of large populations and accurate clinical descriptions are essential.

Calcified Sclero-Choroidal Choristomas in Mosaic RASopathies: A Description of a New Imaging Sign

PURPOSE

To evaluate the imaging and clinical features of unusual calcified lesions seen in the fundus of patients with mosaic RASopathy.

DESIGN

Single-center retrospective observational study.

SUBJECTS

Ten eyes with calcified fundus lesions in 7 patients with mosaic RASopathy.

METHODS

The lesions were evaluated with fundus photography, oral fundus fluorescein angiography, B-scan ultrasonography, magnetic resonance imaging (MRI), and computed tomography (CT) scan where available.

MAIN OUTCOME MEASURES

The imaging characteristics of calcified fundus lesions were assessed.

RESULTS

We found 7 patients with mosaic RASopathies, 5 men and 2 women (3 with linear sebaceous nevus syndrome, 3 with oculoectodermal syndrome, and 1 with encephalocraniocutaneous lipomatosis) with molecular confirmation in 5 cases, all 5 having KRAS-pathogenic variants. Calcified fundus lesions were identified in 10 eyes (bilateral in 3 patients), appearing as slightly elevated, creamy-yellow lesions around or adjacent to the optic nerve, extending supero-nasally; all but 2 of these lesions involved both the choroid and sclera, with 2 of them only involving the sclera at the time of examination. One case developed a choroidal neovascular membrane necessitating intravitreal bevacizumab injections. All 7 patients had B-scan ultrasonography, and the lesion appeared as a hyperechogenic area with an acoustic shadow posteriorly despite reduced gain. Five patients had MRI, and where fundus lesions were present, there was a focal defect in the sclero-choroidal layer. Four patients had a CT scan, and all 4 showed calcifications affecting both the posteromedial sclero-choroid and adjacent medial rectus muscle. Two of these patients had normal eye movements, 1 had a unilateral fixed adducted eye and a vestigial fibrous medial rectus muscle seen in imaging and intraoperatively, and the fourth had marked exotropia with a right gaze deficit affecting both eyes.

CONCLUSIONS

We propose that the lesions seen in this cohort are calcified sclero-choroidal choristomas and should be suspected in mosaic RASopathies when creamy-yellow lesions are seen in the fundus. If identified, the possibility of choroidal neovascularization should be considered during follow-up. In all cases where a CT scan was performed, a novel sign of sclero-muscular calcification involving the medial rectus muscle was seen.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

CRISPR-mediated Ophthalmic Genome Surgery

PURPOSE OF REVIEW

Clustered regularly interspaced short palindromic repeats (CRISPR) is a genome engineering system with great potential for clinical applications due to its versatility and programmability. This review highlights the development and use of CRISPR-mediated ophthalmic genome surgery in recent years.

RECENT FINDINGS

Diverse CRISPR techniques are in development to target a wide array of ophthalmic conditions, including inherited and acquired conditions. Preclinical disease modeling and recent successes in gene editing suggest potential efficacy of CRISPR as a therapeutic for inherited conditions. In particular, the treatment of Leber congenital amaurosis with CRISPR-mediated genome surgery is expected to reach clinical trials in the near future.

SUMMARY

Treatment options for inherited retinal dystrophies are currently limited. CRISPR-mediated genome surgery methods may be able to address this unmet need in the future.

CRISPR applications in ophthalmologic genome surgery

PURPOSE OF REVIEW

The present review seeks to summarize and discuss the application of clustered regularly interspaced short palindromic repeats (CRISPR)-associated systems (Cas) for genome editing, also called genome surgery, in the field of ophthalmology.

RECENT FINDINGS

Precision medicine is an emerging approach for disease treatment and prevention that takes into account the variability of an individual's genetic sequence. Various groups have used CRISPR-Cas genome editing to make significant progress in mammalian preclinical models of eye disease, the basic science of eye development in zebrafish, the in vivo modification of ocular tissue, and the correction of stem cells with therapeutic applications. In addition, investigators have creatively used the targeted mutagenic potential of CRISPR-Cas systems to target pathogenic alleles in vitro.

SUMMARY

Over the past year, CRISPR-Cas genome editing has been used to correct pathogenic mutations in vivo and in transplantable stem cells. Although off-target mutagenesis remains a concern, improvement in CRISPR-Cas technology and careful screening for undesired mutations will likely lead to clinical eye therapeutics employing CRISPR-Cas systems in the near future.