Central retinal findings in Bothnia dystrophy caused by RLBP1 sequence variation

To describe the central retinal findings early in the course of Bothnia dystrophy caused by the homozygous missense R234W sequence variation in the RLBP1 gene.

In 8 young patients with Bothnia dystrophy (aged 9-34 years), high- and low-contrast distance visual acuity and visual fields were measured with Humphrey central (24-2) threshold testing and Goldmann perimetry. Central retinal thickness was measured with optical coherence tomography. Cross-sectional images were analyzed and a linear scanning protocol was applied to examine retinitis punctata albescence in the posterior pole.

Affected visual acuity (4 of 8 cases) and poor low-contrast visual acuity (8 of 8 cases) were found. Significant foveal depression and visual field loss were evident with Humphrey threshold testing at all ages, and paracentral and central scotomata in the second decade of life advanced in adulthood as verified with Goldmann perimetry. Optical coherence tomography showed generalized retinal thinning in the central foveal, foveal (innermost ring diameter [Ø], 1 mm), and inner ring (Ø, 3 mm) areas in all ages, and early retinal thinning was found in the inferior areas of the outer macula (Ø, 6 mm). Foveal and extrafoveal thinning of the retinal layers and outer nuclear layer were found. Homogeneous retinitis punctata albescence changes were visualized in and/or adjacent to the retinal pigment epithelium-choriocapillaris complex with high reflectance.

In the RLBP1-Bothnia dystrophy phenotype, a loss of function and thinning of the central macula are found, indicating early damage of the cone photoreceptors in this disease of the visual cycle. Retinitis punctata albescence spots in the posterior pole are situated close to or in the retinal pigment epithelium-choriocapillaris complex.