Optic nerve and retina degeneration in DBA/2J mice is asymmetric. Scatter plots showing the difference in both optic nerve scores (A) or retina scores (B) for individual mice. The difference in score was calculated by subtracting the left eye (OS) score from the right eye (OD) score for each mouse. The expected result for symmetric degeneration would be a score of '0' for each animal, but clearly there is dramatic scatter of both the optic nerve and retina scores. Optic nerves also show a trend for asymmetry at an early age, consistent with the hypothesis that early damage occurs first in the nerve. Retina asymmetry is more pronounced at ages when the mice show clear signs of retinal degeneration.