A twin study of cilioretinal arteries, tilted discs and situs inversus

Alex J Baneke,Katie M Williams,Christopher J Hammond,Moin Mohamed,Omar A Mahroo

doi:10.1007/s00417-017-3859-7

Abstract

PurposeTo establish the prevalence and heritability of cilioretinal arteries (CRAs), tilted discs (TDs) and situs inversus (SI).MethodsFundus photos from the Twins UK Adult Twin registry twin database were analyzed: 1812 individuals, 526 complete monozygotic (MZ) twin pairs and 336 complete dizygotic (DZ) pairs. Images were assessed non-stereoscopically on a computer screen by the same ophthalmologist for presence of CRAs, TDs or SI. Prevalence figures, probandwise concordances and heritabilities were calculated.ResultsPrevalence of a CRA in subjects’ right eyes was 28.6% (26.5–30.8). Prevalence of subjects with a CRA in at least one eye was 45.0% (42.6–47.5), with a TD in at least one eye was 1.2% (0.8–1.9), and with SI at least one eye was 0.5% (0.3–1.0). There was no association between birth weight and presence of CRA.Concordance for CRA in at least one eye (MZ twins) was 60% (95% CI 55–64), and (DZ) was 45% (95% CI 39–51). Heritability for CRAs in at least one eye was 49.4% (95% CI 38.1–59.7) and for both eyes was 32.9% (95% CI 10.4–53.3). We were unable to calculate meaningful heritabilities or concordances for TDs and situs SI, due to insufficient numbers.ConclusionsThe presence of CRAs appears to be moderately heritable, with greater variance explained by individual environmental factors or even stochastic events. They were not associated with low birth weight. Future genetic research and studies of birth/lifecourse cohorts may offer further insights into the etiology of congenital papillovascular abnormalities.

Highlights

The morphology of the optic disc and its associated vasculature is clinically important as it plays a role in a number of Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.ocular diseases, including anterior ischaemic optic neuropathy, central retinal artery occlusion and the tilted disc syndrome
Concordance for cilioretinal arteries (CRAs) in at least one eye (MZ twins) was 60%, and (DZ) was 45%
Heritability for CRAs in at least one eye was 49.4% and for both eyes was 32.9%

Summary

Introduction

Ocular diseases, including anterior ischaemic optic neuropathy, central retinal artery occlusion and the tilted disc syndrome. In around two thirds of eyes, the inner retina is supplied by the central retinal artery only. The presence of a cilioretinal artery can influence the outcome of several retinal vascular pathologies [6,7,8] In cases of central retinal artery occlusion, areas of the retina supplied by a cilioretinal artery still receive a blood supply and, the corresponding visual field is preserved [7]. Temporal cilioretinal arteries may provide an increased blood supply to the temporal side of the optic disc and, preserve visual field and acuity in advanced open angle glaucoma [6]. It has been suggested that the presence of a cilioretinal artery may increase the risk of diabetic macular oedema [8]

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