Unexpected Genetic Cause in Two Female Siblings with High Myopia and Reduced Visual Acuity

Figure 3

Ganzfeld Electroretinography (ERG). Four standard test conditions, two in the dark and two with rod suppression, were employed, as given (photopic flash intensities; OPs merely indistinguishable, omitted), in control subjects and the three patients. The response of the rod system was severely but not totally reduced. (a) The, mostly bipolar, response in the dark is severely reduced in all three patients. (b) The -wave is affected less than the -wave. Hence, the latter remains below the isoelectric line (“negative response”). (c) The -wave under photopic conditions is longer because positive components that give rise to a steep -wave in the control subjects are smaller and initiate later. The subsequent negative deflection is missing. (d) The flicker response in all patients was below 20% of normal and clearly double-peaked in the father. The father had severely reduced rod and bipolar responses at age 26,75 y. Cone responses to single flashes and 30 Hz flicker were clearly reduced in amplitude, and the latter had a double-peak waveform.

(a) 0.01 cd s m⁻¹ rod-driven

(b) 3.0 cd s m⁻¹ combined response

(c) 3 cd s m⁻¹ cone-driven

(d) 30 Hz Flicker