Abstract
Purpose::
To determine the effect of pre-evaluation flash fundus photography on the multifocal ERG (mfERG).
Methods::
Ten subjects underwent two 103-hexagon stimulus mfERG scans on separate dates, one immediately preceded by flash fundus photography. Five subjects were randomized to receive flash fundus photography before their first mfERG, and 5 before their second. After adequate dilation, each eye was exposed to 4 optic disc and 6 macular flashes at a flash intensity of 60 watt-seconds. Within 5 minutes of flash exposure, subjects underwent an mfERG scan. Data were averaged and analyzed in five concentric rings. MfERG results with preceding flash photography were compared to results without flash photography. Paired t-tests were used to evaluate statistical significance.
Results::
A significant reduction in P1 response density was found in all six rings of the mfERG results with preceding flash photography (p<0.012). P1 response densities were depressed 9.9-12.9 % in each ring with ring 1 showing the greatest change. N1, P1, and N2 response densities were significantly depressed and N1 implicit time was increased in ring 1. P1 implicit times were not affected. Analysis of each eye independently revealed no significant difference.
Conclusions::
Exposing the retina to flash fundus photography immediately preceding the mfERG resulted in significant reduction in response density and an increase in N1 implicit time. These changes could mimic disease in an otherwise normal retina. Other intense light stimuli, such as that of a dilated fundus exam, may alter mfERG results as well. These should be avoided prior to the mfERG.
Keywords: electroretinography: clinical • electrophysiology: clinical • retina: distal (photoreceptors, horizontal cells, bipolar cells)