To establish the usefulness of miniature pigs as model animals in ophthalmology field, we report the ocular anatomical features of miniature pigs.

Göttingen minipigs and Nippon Institute for Biological Science (NIBS) miniature pigs were divided into two groups of younger (5 - 13 months old) and older (15 - 17 months old). Then the ocular axial length, eyeball weight, eyeball volume, lens thickness, lens weight, lens volume, vitreous weight, and vitreous volume in each group were measured. All parameters, except for the lens thickness and lens volume in NIBS miniature pigs, showed a high degree of positive correlation to their body weights from medium degree in both Göttingen minipigs and NIBS miniature pigs. There was no significant difference between Göttingen minipigs and NIBS miniature pigs in anatomical features, for example the ratio of lens thickness to ocular axial length.

In comparison with the previously reported parameters of other laboratory animals, ocular anatomical characteristics of miniature pigs were considered to be closer to the characteristics of dogs rather than to those of rabbits and cynomolgus monkeys. Compared with the parameters of the human eye, ocular axial length, eyeball weight, vitreous weight, and vitreous volume in humans were close to those of the heavy miniature pigs, and lens thickness and lens weight were close to those of the featherweight miniature pigs.

In conclusion, the basic ocular data of miniature pigs revealed that the ocular parameters of Göttingen minipigs and NIBS miniature pigs were correlated positively with body weights, but there was no obvious intraspecific difference. The results in this study also clarified the relationship of ocular anatomical features among laboratory animals, miniature pigs and humans. For these reasons, miniature pigs were considered to be useful as a model animal in the ophthalmic field.

We examined the frequency and time course change of spontaneous ocular lesions in Crl:CD(SD) rats (90 males and 90 females) by serial ophthalmological examination from 5 to 31 weeks of age. In addition, we performed autopsy at 32 weeks of age and carried out histopathological examination of the eyeball (including the optic nerve).

Persistent hyaloid artery, vitreous hemorrhage and retinal red patch/spot were observed at 5 weeks old by ophthalmological examination, but these changes disappeared with aging. Persistent hyperplastic primary vitreous and persistent pupillary membrane were observed in 5 weeks old rats, and these changes disappeared in some rats but not in other rats until 31 weeks old. Focal opacity in lens (nucleus, anterior cortex) and hyperreflectivity in fundus increased with aging. Focal opacity in lens (posterior cortex, anterior and posterior capsule), iris hemorrhage, fixed pupil (the weak reaction of the iris by mydriatic) and vitreous opacity were observed infrequently. These findings were reversible. Diffuse opacity in posterior capsule of the lens did not disappear during the observation period. Calcification of the cornea epithelium, deposit of brown pigment of the ciliary body, persistent hyperplastic primary vitreous, retinal atrophy and retinal fold/rosette were observed by histopathological examination of the eyeball (including the optic nerve). It was difficult to histopathologically detect the focal opacity in lens.

In conclusion, serial observation of ocular lesions in each animal clarified several changes which increase with aging, occur at young age but disappear with aging, or do not disappear with aging.