Frequency of retinal degeneration in F344/N rats treated with kava kava extract (A, B), acrylamide (C, D) and leucomalachite green (E) for two years. In control animals, 50–86% of retinal degeneration occurred in the central or hemispherical retina, the typical site for light-induced retinal degeneration. Diffuse retinal degeneration, more likely due to a direct chemical effect, was proportionally less frequent and the preponderance of central/hemispherical retinal degeneration suggested that these findings were treatment-related exacerbation of light-induced retinal degeneration. The total number of F344/N rats with retinal degeneration in each group are indicated in tables 1, 3, and 5 for kava kava extract, acrylamide and leucomalachite green, respectively.