Retinal phenotypic characterization of patients with Stargardt disease due to p.ala1773val ABCA4 novel mutation in Mexican Population

Session Details

Session Title: Free Paper Session 17: Imaging II

Session Date/Time: Saturday 09/09/2017 | 08:00-09:30

Paper Time: 08:36

Venue: Room 120

First Author: : S.Lopez Rubio MEXICO

Co Author(s): :    O. Chacon-Camacho   R. Matsui   D. Guadarrama-Vallejo   M. Astiazaran   J. Zenteno                 

Abstract Details

Purpose:

To describe retinal clinical features, visual function and anatomical imaging of a cohort of Mexican Stargardt disease patients carrying the uncommon p.Ala1773Val ABCA4 founder mutation

Setting:

Study conducted at Department of Retina and Genetics Research Unit, Institute of Ophthalmology Conde de Valenciana

Methods:

Ten patients carrying the p.Ala1773Val mutation were included, all underwent a complete eye examination, visual function and anatomical imaging evaluation. Visual function was measured by full-field electroretinography (ERG using ISCEV protocol) and Goldmann kinetic visual fields with standard stimuli. In addition, anatomical analysis were performed: spectral domain optical coherence tomography (SD-OCT) with a 9-mm line scan along the horizontal meridian crossing the fovea using the eye-tracking feature (ART); and short-wave autofluorescence (SW-AF, 488 nm) using the 'high speed' mode, 30º x 30º field onto a 768 x 768 pixel image, (Spectralis; Heidelberg Engineering GmbH, Heidelberg, Germany). Quantitation of ONL, MLE and ellipsoid zone eccentricity were measured manually in SD-OCT images. Quantitative analyses of hypofluorescent central areas were measured manually by delineation of zones of decreased autofluorescence.

Results:

Patients ranged in age from 9 to 32 years. Best-corrected visual acuities ranged from 20/200 to 4/200, 80% had photophobia and nyctalopia. Related to Fishman classification 6 cases were stage 4, 3 cases stage 3 and 1 patient stage 2. Atypical retinal pigmentation pattern was observed in 6 individuals from 4 families. We found 8 cases with better preservation of peripheral rod compared to cone function in full-field ERG. Absolute 5-degree central scotoma was the most common visual field abnormality (7 individuals). In vivo retinal microstructure assessment by SD-OCT demonstrated central retinal thinning, variable loss of photoreceptors, and three different patterns of structural retinal degeneration classified depending on the eccentricity of detectable ONL, MLE and ellipsoid zone. The most common pattern in 5 patients was detectable ONL, MLE, and EZ line within the central retina. Two dissimilar patterns of abnormal autofluorescence were observed based on one central localized area (7 cases) or multiple central patches of decreased autofluorescence (3 cases).

Conclusions:

Clinical, functional, and anatomical imaging retinal features of 10 Stargardt disease patients carrying the p.Ala1773Val mutation are described. The particular ABCA4 mutation is associated with a severe retinal phenotype. Careful phenotyping of patients carrying specific ABCA4 mutations is essential to enhance our understanding of disease expression linked to particular mutations and the resulting genotype-phenotype correlations.

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