The effect of docosahexaenoic acid on the electroretinogram of the guinea pig

Docosahexaenoic acid (DHA), an n-3 polyunsaturated fatty acid, is found in consistently high concentrations in the retinae of mammals, yet its role in vision remains unclear. In this study, a mammalian model of variable retinal DHA concentration has been developed, such that the retinal phospholipids of guinea pigs contained between 2.5 and 30.8% DHA. Visual function was assessed using full-field flash electroretinography, over a range of exposure levels spanning six log units. Trend analysis indicated that retinal function was altered by the tissue DHA level, and was described by a second-order polynomial ''inverted U-shaped'' function. The results suggested that although some amount of DHA is essential for normal retinal function, increases in the DHA level past an optimal amount, found to be 19%, provided diminishing returns. In this study, manipulation of the retinal DHA level accounted for 21-35% of the electroretinographic variability.