Purpose: Small areas of retinal pathology may pose diagnostic difficulties. The noninvasive multifocal electroretinogram (MF-ERG) provides a topographical mapping of retinal function. Its role in the diagnosis of macular diseases is examined in age-related macular degeneration (AMD). AMD is a main cause of central visual loss in the elderly population, affecting the second eye in 75%.
Methods: MF-ERG recordings of three patients with AMD were compared to the findings of fundus photography and fluorescein angiography. During the MF-ERG recordings the central 50 degrees of the retina was stimulated. The visual stimulus consisted of 241 hexagons that alternated, independently and pseudorandomly, between black and white according to a special predetermined binary sequence. Local retinal response components were extracted using the Fast m-Transform Algorithm.
Results: Three of six eyes had undergone cataract surgery with implantation of a posterior chamber lens (PCL). In accordance with an increase in light transmission through PCLs, these eyes showed an increase in the MF-ERG responses. MF-ERG allowed accurate topographic mapping of focal areas of retinal dysfunction in all patients tested. There was good correspondence to anatomical changes detected by fluorescein angiography.
Conclusion: The high resolution of the MF-ERG enables detection of small areas of retinal pathology. It thus presents a clinically useful, noninvasive method in the early diagnosis and follow-up of macular disease.