Spontaneous, asymmetrical microphthalmia in C57B1/6J mice.

An investigation was undertaken to evaluate ocular size and shape by objective and subjective criteria to establish the incidence and laterality of spontaneous microphthalmia in the C57B1/6J mouse strain. The purpose was to provide useful information of normal and abnormal ocular development in a laboratory strain frequently used for teratogenic studies. Ten-week-old C57B1/6J mice were time mated and sacrificed at gestational day 14. Eye normality was evaluated subjectively using veterinary ophthalmology methods, and objectively by a computer derived method. A distinct laterality was noted in the right eye when compared to the left eye. Degree of laterality varied with assessment methodology (19.0% vs. 6.9% and 8.9% vs. 4.0% for the subjective and objective methods respectively). Mean eye area and histogram distributions for the right eye were consistently smaller than the left eye for all anatomical rating groups, thereby suggesting that asymmetry found in the C57B1/6J may be due to an inherent discrepancy in eye size in the strain. The data from this study suggest that when C57B1/6J mouse eyes are used as end points for teratological testing each eye should be treated as an independent unit of measure.