Abstract
Abstract: :
Purpose: There is evidence from various studies using visual evoked potentials and electroretinogram that dopamine plays an important role in the retina and is involved in the visual pathway as a functional transmitter. We investigated the short-term effect of Levodopa on the multifocal ERG (mfERG) and assessed the validity and reproducibility of this technique in detecting the influence of pharmacological substances on retinal function. Methods: In a placebo-controlled, randomized, double-masked, two-way cross-over design, 20 healthy non-smoking male volunteers (age 19-35) were studied. Two study days were scheduled. On each study day baseline measurements of mfERG were taken after a resting period of 20 minutes in medium bright artificial ambient lighting conditions (photopic conditions). After oral administration of levodopa (Madopar, Roche, Austria) or placebo, mfERG was assessed at minutes 45, 90 and 135. mfERG measurements were performed using the RetiSCAN system (Roland Consult, Wiesbaden, Germany) with a 103 hexagon pattern and luminances of 0 and 200 cd/sq m. Results: The b-wave amplitude was designated the main outcome variable. The average response of the macular area (rings 1,2) showed a non-significant increase with Levodopa at minute 135 (155% vs baseline, meanSEM; p=0.4, ANOVA vs placebo). The increase in the periphery (rings 3,4,5) at minute 135 was significant (173%; p<0.03). The coefficients of variation of the combined responses were 15.6% for the macular area and 14.4% for the periphery. Conclusion: Our findings indicate that the mfERG is a reliable technique to investigate dopamine induced functional changes in the visual system and suggest that mfERG is useful for assessment and follow-up of modulation of retinal function by pharmacological substances.
Keywords: 389 dopamine • 396 electroretinography: non-clinical