Figure 2.
ERG Traces from the Right Eye of All Four Affected Individuals and a Control Subject
ERG traces from family A (A, III-2; B, III-1; C, II-5), the family B proband (D; it is noted that only standard ERG protocols were tested in the subject), and a control subject (E). The nomenclature of the responses relates to the adaptive state of the eye (DA, dark adapted; LA, light adapted) and stimulus intensity in cd.s.m−2 (DA 0.01 relates to dark adapted responses to 0.01 cd.s.m−2 flash). The DA b-wave was either reduced or non-detectable between stimulus intensities of 0.0025 and 0.1 cd.s.m−2. On bright flash stimulation in the dark (3.0 and 10.0 cd.s.m−2), the a-wave is of normal amplitude; b-wave is markedly reduced at both intensities. The DA ERG results (DA 0.0025 to DA 10.0) are consistent with rod ON bipolar dysfunction in all affected subjects (A–D). The LA 3.0 single flash ERG showed normal a-wave amplitudes in all subjects, but the slope of the a-wave was reduced, and implicit times were markedly delayed in two subjects (C and D); the same subjects showed reduced b-wave. The 30 Hz flicker responses were completely normal in two subjects (represented in A and B), and showed marked delay in two subjects (represented in C and D). These findings suggest reduced cone sensitivity in two subjects (C and D). Long duration stimulation (ON-OFF ERG) showed selective reduction of b-wave in two subjects (A and C), consistent with cone ON bipolar dysfunction; d-wave (OFF response) was normal in all three tested (A–C).