Rod and cone a-waves in three cases of bietti crystalline chorioretinal dystrophy

Abstract

PURPOSE: To estimate retinal function in Bietti crystalline chorioretinal dystrophy using the electroretinogram. METHODS: In this observational case series, the scotopic and photopic electroretinograms in three Japanese female patients (case 1, 55 years old; case 2, 56 years old; case 3, 47 years old) who showed bilateral crystalline retinal deposits but no corneal deposits were recorded. The rod and cone a-waves were analyzed by using the method described by Hood and Birch (1995, 1997). The parameters Rm p3 (maximum a-wave amplitude) and S (sensitivity) were calculated. RESULTS: In case 1, the rod Rm p3 was decreased in both eyes. The rod S in the right eye was within the normal range, but that in the left eye was significantly reduced. Although the cone Rm p3 was decreased, the cone S was within the normal range. In case 2, the rod and cone Rm p3 was reduced, but the rod and cone S was within the normal range in both eyes. In case 3, the rod and cone Rm p3 and S were within the normal range. CONCLUSIONS: Electroretinograms illustrated different disease stages, however, no eye with normal Rm p3 and decreased S was found in rods and cones. In the early stages of this disease, decreased numbers of photoreceptors and/or outer segment shortening may be present while phototransduction remains normal. As the damage to the retina progresses, phototransduction becomes severely affected. Because reduced cone S was not observed in our cases, cones may be less involved than rods in this disease.