Functional Analysis of Retinal Flecks in Stargardt Disease

To evaluate visual function of flecked areas in a series of patients with Stargardt disease (STGD) and compare them with adjacent non flecked areas.

Twenty-seven patients with STGD, ABCA4 mutations and yellowish retinal flecks at fundus examination were recruited. Microperimetry with the Nidek MP-1 and fundus autofluorescence imaging (FAF) were performed in all the patients (27 eyes) while spectral-domain optical coherence tomography (SD-OCT) was performed in a subgroup of patients (20 eyes). Visual sensitivity (in dB) for each hyperfluorescent flecked area on FAF was compared with the value of the nearest adjacent non-flecked area in the MP-1 grid and at approximately the same distance from the fovea. Retinal structure in some of the flecked areas tested by microperimetry was analysed with SD-OCT. All patients were screened for mutations in the ABCA4 gene by APEX array and direct sequencing.

A total of 1836 locations (68 locations for each eye with the 10-2 program) were tested with the MP-1 and 97 corresponded to hyperautofluorescent flecks. A repeated measure, linear regression analysis was used to evaluate differences between visual sensitivity associated with the 97 flecked areas with those in the 97 neighbouring non-flecked areas. The difference was statistically significant (p<0.001) (flecked areas 12.89 +/- 3.86 dB vs. non-flecked areas 14.40 +/- 3.53 dB, respectively). SD-OCT in the flecked areas revealed the presence of hyperreflective dome-shaped lesions in the outer retina located at the level of the retinal pigment epithelium (RPE), with dislocation or disruption of the photoreceptor layer.

In STGD hyperfluorescent flecks on FAF are associated with decreased visual sensitivity compared to adjacent non-flecked areas and with an alteration of the photoreceptor layer on OCT. Flecks do not represent only a typical ophthalmoscopic feature but correspond, in some cases, to retinal damage that contributes to patients' visual loss.