Figure 3: Optical coherence tomography (OCT) macular cube 512   128 scan showing macular thickness in individuals III:1 (a) and II:1 (b). For each scan, top left: fundus image with scan cube overlay. Top right: macular thickness significance map. The central innermost 1-mm-diameter circle represents the central subfield; inner superior, inner nasal, inner inferior, and inner temporal areas bounded by the 3-mm-diameter circle form the inner macula; outer superior, outer nasal, outer inferior, and outer temporal areas bounded by the 6-mm-diameter circle form the outer macula. Retinal thickness values from ILM to RPE are compared to the normative data. Middle and bottom left: cross-sectional OCT scans. Middle right: 3D surface maps: the ILM-RPE, displaying the retinal thickness in three dimensions, the ILM, which appears normal in the two patients, and the RPE, which is altered in II:1. Bottom right: central subfield thickness, overall average macular thickness, and overall macular volume compared to normative data are displayed in table format. Reduction in the retinal thickness and macular atrophy of all retinal layers occurs in patient II:1. Abnormally thin macular region appears even in patient III:1 before obvious ophthalmoscopic changes. ILM: inner limiting membrane; RPE: retinal pigment epithelium.