Abstract
Purpose: :
To correlate the structural and functional defects in patients with Stargardt’s disease in better understanding the pathophysiological mechanisms in this disease.
Methods: :
Spectral-domain Optical Coherence Tomography (SD-OCT) [Spectralis, Heidelberg] was used to perform both OCT as well as fundus autofluorescence (FAF) on seven patients with Stargardt's disease. The mean age was 48 years (range, 21-68 years) and there were four men and three women in the study. Goldmann visual field (GVF) and micro-perimetry (MP-1) were performed on patients, wherever possible, to correlate the areas of anatomical defects with corresponding deficits in retinal function.
Results: :
SD-OCT of the macular area showed atrophy of the retinal pigment epithelium (RPE) and photoreceptors with prominent choroidal vessels evident in the area of atrophy, consistent with a diagnosis of Stargardt’s disease. FAF demonstrated ‘hypoautofluorescence’ corresponding to areas of RPE atrophy and absent photoreceptor layer on OCT, surrounded by a ring of ‘hyperautofluorescence’ corresponding to an area of hypertrophied RPE and distorted photoreceptor layer on OCT. Retinal function testing showed decreased visual acuity and dense central scotoma on GVF testing. Micro-perimetry demonstrated absent function in the area of atrophy, elevated thresholds in areas immediately adjacent to it and normal thresholds beyond the atrophic areas.
Conclusions: :
The main pathology in Stargardt’s disease is abnormal accumulation of lipofuscin-like material in RPE cells leading to atrophy of RPE cells. Following RPE atrophy, the adjacent photoreceptor cells and choriocapillaris also atrophy. The present study depicts the areas of RPE-photoreceptor atrophy as evidenced by the OCT and ‘hypoautofluoresence’ on FAF and loss of retinal function in that area, as seen on GVF and MP-1 testing. It is interesting to note the presence of a ring of ‘hyperautofluorescence’ immediately surrounding the hypoautofluorescent atrophic macula. This is seen as an area of hypertrophic RPE layer and distorted photoreceptor cell layer on OCT and increased but not absent thresholds on MP-1 testing. This is the adjoining ‘sick’ RPE which is laden with lipofuscin and probably the next area to become atrophic. The retinal function beyond the hyperautofluorescent area had relatively normal function. Long term follow-up studies of patients with Stargardt’s disease will help in better defining the course of the disease.
Keywords: retinal degenerations: hereditary • imaging/image analysis: clinical • perimetry