Abstract
Purpose: :
The multifocal electroretinogram (mfERG) was introduced into clinical applications about 10 years ago and has been established as a useful diagnostic tool in retinal diseases. Our study aimed at comparing multifocal ERGs and other parameters of disease development.
Methods: :
Seventeen patients (8 male and 9 female) with clinically defined Retinitis Pigmentosa and either simplex, autosomal recessive (9) or autosomal dominant (7) inheritance or Usher II syndrome were included in the study. Disease progression was followed over a period of up to 10 years using psychophysical (visual acuity, visual field, colour vision) and Ganzfeld electroretinography. Additionally multifocal ERGs were recorded using a VERIS system (Version 1 to 4.8) and a Grass amplifier. The black & white stimulus consisted of 61 hexagons covering a visual field of approx. 60x55 deg. Responses were analyses according to 5 ring averages.
Results: :
Subjects age ranged from 12 to 73 years. The change in amplitude over disease duration generally corresponded with the visual field loss. While the visual acuity (mean was 0.82 with a range of 0.05 to 1.6) correlated with the inner ring 1 of the mfERGs, we found a linear correlation of the scotopic Ganzfeld–ERG maximum response with ring 5 averages of the mfERG. However, multifocal ERG responses could be recorded in many cases even if the Ganzfeld–ERG was extinguished.
Conclusions: :
The multifocal ERG is useful to monitor long term disease progression in Retinitis Pigmentosa. While the central responses correlate to macular function, the loss in amplitude in the outermost ring correlates to the loss in cone and rod function in the peripheral retina.
Keywords: retinal degenerations: hereditary • electrophysiology: clinical • electroretinography: clinical