Usefulness of ophthalmic examination in postnatal observation in teratology studies.

Pregnant rats were irradiated with soft x-ray at a dose of 635 r or 1270 r on Day 9 or 11 of gestation. The eyes of F1 offspring were examined by indirect ophthalmoscopy and slit lamp biomicroscopy in postnatal weeks 3 to 7. Ophthalmoscopic examination of offspring irradiated at a dose of 635r or 1270r on Gestational Day 9 revealed iris and choroidal coloboma together with microphthalmia and anophthalmia at Postnatal Week 3 or later. Choroidal coloboma, an anomaly that cannot be detected by the common external observation method, was found ophthalmoscopically in one rat without any external ocular abnormalities. This fact suggests that ophthalmoscopy in postnatal observation can be useful to detect ocular teratogenic potential of test compounds in preclinical safety studies.