Mouse models for the analysis of myopia: An analysis of variation in eye size of adult mice

Purpose. To assess the relative importance of genetic and environmental fac tors that modulate eye growth, eyes, lenses, and retinas of 507 mice belong ing to 50 strains were measured. Methods. Mice of both sexes and a wide ran ge of ages (27 to 526 days) were perfused for electron microscopy and eyes, lenses, and retinas were dissected and measured. Our uniform fixation prot ocol was shown to cause a weight loss of 4 to 6%. Multiple linear regressio n methods were used to explore relations between eye and lens weight, retin al area, age, sex, body and brain weight, and retinal ganglion cell number. Results. The eye and lens of mice continue to grow long after sexual matur ity is reached at 40 to 60 days of age. The pace of growth matches the loga rithm of age. Despite their smaller bodies, females have eyes as large as t hose of males. The correlation of eye weight to brain weight is remarkably low (r = 0.19), whereas that to retinal area is high (r = 0.86). Surprising ly, the correlation between lens weight and the size of the posterior segme nt (eye minus lens weight) is only 0.5 to 0.6, and ratios of these paramete rs are highly variable. Heritability of all trails is between 25 to 50%. Co nclusions. The continued growth of eyes in adult mice provides an excellent system to test effects of genetic and molecular manipulations on the devel opment and treatment of myopia. Heritability is sufficiently high to map ge nes that specifically modulate growth of different parts of the eye.