To determine whether foveal outer retinal dysfunction is common in eyes with unexplained visual symptoms or acuity loss.
Seventy-three eyes of 44 consecutive patients with unexplained visual symptoms or acuity loss, 39 eyes of 39 control subjects, and 12 eyes of 7 patients with known maculopathy.
Foveal cone electroretinography (ERG) and letter recognition perimetry.
Main Outcome Measures
Foveal cone ERG data.
Abnormal foveal cone ERG data were recorded in 35 (48%) of 73 eyes (23  of 44 patients). Among these 35 eyes, amplitude was lower than in normal controls (P<.001) and was correlated with visual acuity and the number of letter recognition perimetry errors (P<.05 for both). The latter was higher in eyes with abnormal retinal responses than in symptomatic eyes with normal responses (P<.01). However, initial symptoms, visual acuity, and macular appearance did not differentiate between these 2 groups. Foveal cone ERG test vs retest data showed consistent results.
Foveal outer retinal dysfunction is a common underlying mechanism of previously unexplained visual symptoms or acuity loss. Foveal cone ERG testing should be considered early in the evaluation of eyes with this presentation.