Abstract
Purpose:
To determine the influence of body length on eye length in two different wild-type (WT) mouse strains during normal eye development.
Methods:
Measurements of body length, axial length, and refraction were retrospectively analyzed for two different WT mouse strains: 129S1/SvJ (n=6) and C57BL/6J (n=8) from 4 to 16 weeks of age. Body length, from the tip of the nose to the base of the tail were taken from digital images using image analysis software (ImageJ). Axial length (using an average refractive index of 1.433 for the entire eye) and refractions were measured using a 1310 nm spectral domain OCT (Bioptigen, Inc.) and an infrared photorefractor, respectively. To elucidate the effect of body length on eye length between strains, axial length was divided by the body length (eye/body length ratio) for all animals.
Results:
Body length increased significantly with age for both strains (p<0.001). C57BL/6J mice had significantly larger body length (average at 10 weeks, 8.60 ± 0.21 cm) compared to 129S1/SvJ (8.31± 0.13 cm) mice (p=0.011). Axial length also increased significantly during the development period (p<0.001). However, it was not found to be significantly different between the two strains across age (average at 10 weeks, 3.24 ± 0.07 and 3.26 ± 0.05 mm for C57BL/6J and 129S1/SvJ respectively). After normalizing to body length, 129S1/SvJ exhibited a significantly larger eye/body length ratio (average at 10 weeks, 0.039 ± 0.001) compared to C57BL/6J (average at 10 weeks, 0.037 ± 0.001) at all ages (p=0.025). Similar to body length, crystalline lens thickness normalized to body length significantly changed across both strains (129S1/SvJ > C57BL/6J, p<0.05). Four week old 129S1/SvJ (-4.92 ± 2.37 D) mice had significantly greater myopic refractions than C57BL/6J mice (+3.80 ± 1.45 D; p<0.001), but both strains reached similar hyperopic refractions by 14 weeks of age. A significant negative association was observed between the eye/body length ratio and refraction for all mice across both strains (slope = -0.0001, r 2 = 0.16, p<0.001).
Conclusions:
Body length significantly influences axial length in different mouse strains during development. The ratio of eye length to body length is important to refractive development, but not the only predictor of refractive error in mice.
Keywords: 605 myopia •
677 refractive error development •
511 emmetropization