Phenotypic Subtypes of Stargardt Macular Dystrophy–Fundus Flavimaculatus

Abstract

To determine if phenotypic subtypes exist in Stargardt macular dystrophy-fundus flavimaculatus (SMD-FFM). Methods: A cross-sectional study of 63 patients with autosomal recessive SMD-FFM was undertaken. The age of onset, duration of symptoms, visual acuity, and clinical features on fundus examination, color fundus photographs, and fundus autofluorescence images were recorded. Electrophysiological tests, including pattern, focal, and fullfield electroretinogram (ERG), electro-oculogram, and colorcontrast sensitivity measurement, were also performed. Results: Based on electrophysiological attributes (ERG), patients with SMD-FFM could be classified into 3 groups. In group 1, there was severe pattern ERG abnormality with normal scotopic and full-field ERGs. In group 2, there was additional loss of photopic function, and in group 3, there was loss of both photopic and scotopic function. Differences in scotopic or photopic function among groups were not explained on the basis of differences in age of onset or duration of disease. Conclusions: Patients with SMD-FFM can be classified into 3 groups based on the absence or presence of generalized loss of either photopic or photopic and scotopic function. It appears that these 3 groups may represent distinct phenotypic subtypes in SMD-FFM.

Phenotype and Progression of Retinal Degeneration Associated With Nullizigosity of ABCA4

“…Full-field ERG provides an objective measure of peripheral retinal involvement. Three functional phenotypic subtypes were established previously 12 (see Methods) and a longitudinal follow-up of the same cohort (mean follow-up 11 years) found that only 20% of ERG group 1 (normal full-field ERG) cases had progression to either group 2 or 3 (cone and cone-rod dystrophy, respectively), whereas 100% of patients with initial rod ERG abnormality showed significant progression. The correlation between genotype and ERG is poorly understood and difficult to explore due to the genetic heterogeneity of ABCA4.…”

Retinal Phenotypes in Patients Homozygous for the G1961E Mutation in theABCA4Gene

“…Patients with ERG group I disease had normal amplitude of the photopic and scotopic ERGs; ERG group II disease patients had relative loss of cone-driven function, while ERG group III patients had abnormally reduced scotopic and photopic ERGs. 39 With advanced STGD1, photopic and scotopic responses may become diminished below the recording threshold, whereby it becomes difficult to distinguish ERG group III disease form a rod-cone pattern of dysfunction electrophysiologically. In this situation a presenting history of nyctalopia, rather than light aversion and/or central or color vision problems, would suggest a diagnosis of RP rather than ERG group III disease.…”

Low Vision Management in a Case of Stargardt's Disease

“…Stargardt's disease affects individuals of any age, gender and race [1,5,7]. Limit of visual acuity, fundus appearance and severity of the disease varies widely among patients [1,7,8]. Typically, fundus flecks and atrophic patches at the macula and the mid-peripheral retina are difficulties in writing and was able to write in a straight line.…”