Figure 4.

Longitudinal ERG Findings of Autosomal-Recessive Bestrophinopathy

(A and B) Data from one patient (II-1, family 4), showing deterioration over a 5 year period. Initial findings show mildly subnormal rod-system ERGs with more marked cone-system abnormalities (reduced and delayed). All full-field ERGs show amplitude reduction and implicit time increase over a 5 year period, except the single-flash photopic ERG that only shows implicit time increase. The undetectable PERG is in keeping with severe macular dysfunction.

(C) Representative normal control. ERGs were recorded in accordance with the recommendations of ISCEV. The rod-specific ERG arises in the rod ON bipolar cells and acts as a measure of rod-system sensitivity. The BWF ERG has an initial a-wave predominantly arising in relation to photoreceptor function. This response is dominated by the rod system, but there is a small cone contribution. The 30 Hz flicker ERG (recorded with a photopic rod-suppressing background) is a cone-system response arising in inner retina and is the most sensitive measure of generalized cone dysfunction. The single-flash cone has a photopic a-wave to which there is some contribution from the cone photoreceptors (also the OFF bipolar cells). The PERG P50 component acts as a measure of macular function.