NORMAL ELECTROOCULOGRAPHY IN BEST DISEASE AND AUTOSOMAL RECESSIVE BESTROPHINOPATHY

Purpose: To evaluate the electrooculogram (EOG) in a large series of patients with Best disease and autosomal recessive bestrophinopathy. Methods: A retrospective review of consecutive cases at Moorfields Eye Hospital, London, United Kingdom. Patients with Best disease or autosomal recessive bestrophinopathy who, after electrophysiologic testing, had a normal or atypical EOG light rise were identified. Main outcome measure was EOG amplitude, clinical phenotype and genotype. Results: One hundred thirteen patients were identified with likely disease-causing sequence variants in BEST1 (99 Best disease and 14 autosomal recessive bestrophinopathy). Electrooculograms had been performed in 75 patients. Twenty patients (27%) had no detectable light rise (Arden ratio of 100%) and 49 (65%) had Arden ratios of between 100% to 165%. Six patients (8%) were found to have an EOG light rise of >165%. No cases demonstrated significant interocular asymmetry in EOG amplitude. Conclusion: The current work provides significant clinical evidence that the EOG phenotype in Best disease and autosomal recessive bestrophinopathy is more variable than currently appreciated. As a normal EOG may occur in the presence of a classical fundus appearance, the consequences of BEST1 mutation may be independently expressed, possibly mediated through differential effects on intracellular calcium homeostasis.