Visual Function, Fundus Autofluorescence and Structure in Stargardt Disease

Abstract

Purpose: : To investigate the relationship between areas of abnormal autofluorescence, and measures of visual function and structure in patients with Stargardt disease.

Methods: : Nineteen eyes of 13 patients with Stargardt disease, aged 12 - 65 years, were studied. Of the 13 patients, 10 had mutations in the gene encoding ABCA4; results are pending on 3. All tested eyes had best corrected visual acuities equal to or better than 20/200. Fundus autofluorescence (FAF) was assessed with the Heidelberg HRA II imaging system, and preferred retinal locus (PRL) with fundus photography and the Nidek microperimeter (MP-1). Visual field sensitivity was measured with the MP-1 (10-2 program, with auto-tracking). Retinal function was evaluated with the multifocal ERG (mfERG) VERIS (EDI) system using a display of 61 hexagons. The position of the fixation target was adjusted for eccentric PRLs. Fixation was continuously monitored. The structure of the macular area was evaluated with the spectral OCT (Zeiss) using a linear scan and macular cube analysis and the retinal nerve fiber layer (RNFL) was evaluated with the OCT 3 (Zeiss), using a fast RNFL scan protocol.

Results: : 17 eyes had an eccentric PRL. For 16 eyes fixation was in the superior retina and for one eye in the temporal retina. Two eyes maintained foveal fixation. All patients had a dense central scotoma on the MP-1. The combined PRL, MP-1 and FAF images showed that retinal areas underlying the eccentric PRL had normal FAF and normal visual sensitivity. There was good agreement between the MP1 and fundus photography for the PRL. Visual sensitivity was markedly decreased over central hypofluorescent areas that corresponded to the atrophic lesions, and mfERG response amplitudes were decreased or non-recordable. Sensitivity over areas of hyperfluorescence corresponding to yellow flecks, was not decreased. The spectral OCT showed that retinal thickness and volume were decreased in the central hypofluorescent area. Analysis of the RNFL performed in 7 eyes showed defects in RNFL thickness in 4 (3 temporal defects, 1 nasal defect).

Conclusions: : Visual sensitivity was markedly decreased over areas of hypofluorescence that corresponded to atrophic lesions but it was not decreased over areas of hyperfluorescence that corresponded to flecks. The results emphasize the importance of comparing tests of visual function to retinal morphology in evaluating the efficacy of treatment trials for Stargardt disease.

Keywords: degenerations/dystrophies • imaging/image analysis: clinical • perimetry