Purpose
Stargardt disease (SD) is the leading cause of inherited macular dystrophy with progression into adulthood. Retinal pigment epithelium (RPE)/photoreceptor atrophy and fundus flecks are classic signs of SD. The identification of subretinal topographic changes and their distribution may provide early indicators of disease. Using SD-OCT, we examined the subretinal space of SD patients in areas devoid of atrophy or flecks to assess for alterations in subretinal thickness and morphology.
Methods
Patients with an ICD9 code for SD with SD-OCT imaging from 2009 to 2014 were identified. Patients with retinal comorbidities or macular atrophy involving the entire OCT scan area were excluded. Age-matched controls were used for comparison. The largest of 5 measurements in unaffected areas in each OCT scan line, taken at 500µm intervals across the macula, was used to determine subretinal space thickness (Bruch's membrane to ellipsoid line). Two-way repeated measures ANOVA was used to compare measurements between SD patients and controls. An intraclass correlation was calculated using repeated measurements in 10 randomly-selected eyes. Additionally, two independent observers scored the appearance of the apical process interdigitation line in patients and controls at 2000µm temporal to the fovea, a location selected to avoid atrophy. The chi-square test was utilized to compare the rates of abnormal scores between groups, and the Kappa statistic was employed to assess inter-rater reliability.
Results
Thirty-eight patients (mean age 35.7) and 26 controls (34.1) were identified. Patients showed subretinal thickening relative to controls (Figure 1) with the greatest magnitude difference (3.2µm) at 2500µm superior to the foveal center. The intraclass correlation was 0.88 (p<0.0001). An abnormal interdigitation line (indistinct/interrupted) was noted in 89.3% of patients compared to 23.1% of controls (p<0.0005), and the Kappa statistic was 0.89 (p<0.0001).
Conclusions
Patients with Stargardt disease show changes in subretinal thickness and morphology on SD-OCT relative to controls in macular regions without atrophy or subretinal flecks, with the most pronounced thickening superior to the fovea. These findings may prove useful for future prospective studies or early clinical disease detection.