Abstract
Purpose: :
To characterize lipofuscin (LF) accumulation in patients with Stargardt's disease (STG) and correlate the amount of lipofuscin in the RPE with clinical findings in these patients.
Methods: :
Lipofuscin autofluorescence was measured in 38 patients with Stargardt's (STG) dystrophy (Ages: 7–54 years). Fundus findings were classified into 4 types according to Noble and Carr's classification (1971): 1: macular degeneration (MD) without flecks (n=6); 2: MD with parafoveal flecks (n=12); 3: MD with diffuse flecks (n=18); and 4: diffuse flecks without MD (n=2). Subjects with normal retinal status (n=122) served as control. LF was measured using our fundus fluorometer (Exc.: 550 nm; Emi.: >570 nm) at the fovea (F) and at 7 deg. temporal to the fovea (7T) with a sampling area of 2 deg. in diameter. The extent of yellow deposit and atrophy was graded at each test site from fundus photographs. Measurements made in frank atrophy were not included. Visual acuity, electroretinogram in 10 patients, and SLO microperimetry in 11 patients were used to assess macular function.
Results: :
LF levels in all types of STG were significantly higher than age–matched control (p<0.0001) but LF levels among STG patients were not associated with STG type. The ratio of LF in STG to LF in age–matched controls was 264±152% (range: 42–742%) at 7T, and 346±296% (range: 31–1204%) at the fovea. This ratio also decreased significantly with age at both sites (p<0.002). The ratios of foveal to perifoveal LF (F/7T) was 0.72±0.30 (range: 0.4–1.3) for STG patients, significantly higher (p<0.0001) than for controls (F/7T=0.56±0.11). In 10 patients with no atrophy at the fovea, there was a tendency for LF levels to be higher when visual acuity was low (p=0.05). The amplitude of photopic b–wave elicited by red light under dark adaptation was negatively correlated with LF levels at the fovea (p=0.02). LF levels in scotoma affecting the fovea (n=8) were also significantly higher than control (p<0.0001).
Conclusions: :
Our study confirms the significant increase of LF levels in patients with STG dystrophy (Delori 1995, von Ruckmann 1997). The fact that LF levels increase more at the fovea than at the perifoveal (7T) suggests involvement of cones. The age–related decrease in LF levels relative to control probably reflects the increasing amount of degeneration and atrophy of the RPE. Foveal LF levels remain high despite advancing degeneration (foci of atrophy) and visual function loss (scotoma, low visual acuity, depressed photopic b–wave). Lipofuscin levels are expected to decrease after RPE atrophy becomes more severe.
Keywords: retinal degenerations: hereditary • retinal pigment epithelium • macula/fovea