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.