Assessment of Central Visual Function in Stargardt’s Disease/Fundus Flavimaculatus with Ultrahigh-Resolution Optical Coherence Tomography

Abstract

PURPOSE: To assess photoreceptor morphology in patients with Stargardt's disease and fundus flavimaculatus using ultrahigh-resolution optical coherence tomography (UHR-OCT) and correlate it with visual acuity (VA). METHODS: This was a prospective observational case series. Fourteen patients with Stargardt's disease (nine women, five men; average age, 39 years; range, 27-53) were examined. A clinically viable UHR-OCT system employing a new, compact titanium sapphire laser was used, enabling a 3-microm axial resolution in the retina. All patients received a full ophthalmic examination, including fluorescein angiography. Outcome was judged by central transverse photoreceptor loss, central foveal thickness, VA, central atrophy according to fluorescein angiography, and fundus autofluorescence. RESULTS: UHR-OCT was capable of visualizing and quantifying regions of central transverse photoreceptor (PR) loss. All Stargardt patients with central atrophy had a complete loss of the central photoreceptor layer in the foveal region (mean transverse photoreceptor loss, 4390 +/- 2270 microm; range, 530-9240 microm). Patients without clinically evident central atrophy had an intact photoreceptor layer centrally, but had small, focal parafoveal defects. A correlation was detected between VA and transverse PR loss (Spearman rho=-0.60, P=0.03), which was confirmed on logistic regression analysis (R2=0.49, P=0.0001). Central foveal thickness was reduced in patients with Stargardt's disease (85 +/- 40 microm; range, 58-280 microm). The correlation was statistically significant with VA (Spearman rho=0.43, P=0.04), but not with transverse PR loss (Spearman rho=-0.23, P >>0.05). Linear regression analysis showed a statistically significant association of central foveal thickness with VA (R2=0.51, P=0.0001), but not with transverse PR loss (P >>0.05). The extent of atrophy seen in fluorescein angiography correlated with VA and transverse PR loss (Spearman rho=-0.51, P=0.007; Spearman rho=0.77, P=0.0001). Similar correlations were found with the maximum transverse diameter of fundus autofluorescence (Spearman rho=-0.72, P=0.008; Spearman rho=0.77, P=0.003). CONCLUSIONS: Ultrahigh-resolution OCT demonstrates excellent visualization of intraretinal morphology and enables quantification of the photoreceptor layer. Thus, for the first time, an in vivo visualization and quantification of transverse, central photoreceptor loss and correlation with visual function is possible. Lower VA corresponds to a greater transverse photoreceptor loss, which also correlates with the extent of changes seen in fluorescein angiography and in fundus autofluorescence. Furthermore, reduced retinal thickness (i.e., atrophy of retinal layers) does not correlate with the transverse extent of PR loss. Thus, it seems that although there may be progressive atrophy of intraretinal layers, an intact photoreceptor layer leads to better VA. UHR-OCT may present a viable alternative to the assessment of central visual function, due to the easy, objective, and noninvasive data acquisition. Therefore, UHR-OCT could be of future use in judging patients' prognoses in Stargardt's disease.