PURPOSE:: The purpose of this study was to investigate the posterior and equatorial scleral thicknesses in patients with autosomal dominant Best disease, a condition that has chronic subretinal fluid. METHODS:: This was a retrospective study involving patients with Best disease and age-matched controls. Participants were evaluated with contact B-scan ultrasonography and enhanced depth imaging optical coherence tomography to evaluate scleral thickness in the posterior pole and equator. Univariate analysis and generalized estimating equations were used. RESULTS:: Of nine patients with genetically proven Best disease and 23 age-matched controls, there was no significant difference in the age or the gender proportion between groups. Subfoveal choroidal thickness and axial length were not significantly different between groups. Both posterior scleral (right eye; 1.38 mm vs. 0.89 mm, P < 0.001, and left eye; 1.39 mm vs. 0.83 mm, P < 0.001) and equatorial scleral (right eye; 0.61 mm vs. 0.42 mm, P = 0.003, and left eye; 0.55 mm vs. 0.41 mm, P = 0.017) thicknesses were much greater in cases as compared with controls. Multivariate analysis showed male sex and having Best disease were each significant predictor of posterior scleral thickness, and Best disease was the sole significant predictor for equatorial scleral thickness. CONCLUSION:: BEST1 gene may have a developmental role leading to having a thicker sclera, influencing disease manifestation, and contributing to the accumulation of subretinal fluid in Best disease.