PURPOSE: To evaluate visual function by full-field electroretinography (ERG) and visual acuity in patients with cone dystrophy. METHODS: 23 (7 male and 16 female) patients with suspicion of cone dystrophy were evaluated at the Clinical Electrophysiology of Vision Laboratory of the Universidade Federal de São Paulo. Inclusion criteria were: clinical history, visual acuity measured by ETDRS or Snellen charts and retinal function assessed by full-field electroretinography. The peak-to-peak amplitude and b-wave implicit time values were compared with previously published age norms. RESULTS: Visual acuity measurement in the best eye ranged from 0.07 to 3.00 logMAR (HM to 20/25) with mean VA of 0.85±0.64 logMAR (20/140). Mean peak-to-peak amplitude for scotopic rod-response was 144.29±80.05 µV (normal for age) and mean of implicit time was 92.85±9.02 ms (normal for age). Mean peak-to-peak amplitude for single-flash cone response was 5.06±8.59 µV (reduced for age) and mean implicit time was 43.4±14.4ms (reduced for age) for detectable responses; for 30 Hz-flicker mean amplitude was 5.00±9.00 µV (reduced for age) and the mean of implicit time was 34.9±10.9 ms (reduced for age). CONCLUSION: Mean visual acuity was 0.85 logMAR (20/140) in this group of patients with cone dystrophy. Photophobia was the main complaint, followed by decreased vision and defective colour vision. Ten of 23 (10/23) patients had their final diagnosis only after full-field electroretinography recording, since the fundus examination was normal.
Electroretinography; Cones (retina); Colour perception; Visual acuity; Low vision
