Multifocal ERG in chloroquine retinopathy: regional variance of retinal dysfunction

Background: A study was carried out to evaluate the regional variance of retinal dysfunction in chloroquine retinopathy. Methods: In three patients with different stages of chloroquine retinopathy, ophthalmologic evaluations including recording of full-field electroretinogram (ISCEV standard) and multifocal electroretinogram were performed. Results: III one patient with mild chloroquine retinopathy the visual acuity, visual fields and full-field electroretinogram were normal, but retinal dysfunction was indicated by color vision disturbances. The second patient had moderate chloroquine retinopathy with normal visual acuity, visual fields and dark-adapted full-field electroretinogram; light-adapted and flicker full-field electroretinogram responses were, however, borderline and color vision was abnormal. The third patient had severe chloroquine retinopathy with reduced visual acuity, visual field and color vision defects, and a reduced full-field electroretinogram. In the multifocal electroretinogram, recorded with 61 hexagons, amplitudes and implicit times were evaluated in rings surrounding the center. In all three patients severe dysfunction (either amplitudes or implicit times) was found in the parafoveal and perifoveal areas. In the fovea and towards the periphery the function was normal or only moderately reduced. Conclusion: Chloroquine retinopathy of different severity presents with characteristic alterations in the multifocal electroretinogram. Regional distribution of cone dysfunction is in agreement with previously reported histologic findings. The multifocal electroretinogram can detect retinal dysfunction in chloroquine retinopathy even when the full-field electroretinogram is normal and retinal alterations are subtle.