Iridal coloboma induces dyscoria during miosis in FLS mice.
OBJECTIVE
Fatty liver Shionogi (FLS) mice exhibit characteristic retinochoroidal coloboma because of a failure in fusion of the embryonic optic fissure. However, the same pathogenesis should result in iridal coloboma that has not been reported in this strain. The purpose of this study was to describe the physiologic and morphometric changes in iridal tissue involved in ocular coloboma in FLS mice.


METHODS
The miotic response after light exposure was evaluated in three strains of live mice, and the shape and location of the pupil were judged macroscopically. Subsequently, macroscopic abnormalities in the anterior segment and fundus were observed postmortem in all mice. During miotic and mydriatic responses in the eyes of live male FLS mice with dyscoric and normal pupils, each iris was measured in four radial directions. The enucleated eyes were examined morphometrically and histologically in both sexes of FLS mice.


RESULTS
Inferior corectopia upon light-induced miosis was clearly detected in live FLS mice. The deviated pupils were not round but oval-shaped. Clinical and postmortem examination revealed that all dyscoric eyes had hypoplastic and dysfunctional irides inferiorly in FLS mice. Histopathological examination confirmed that both the dilator and sphincter muscles and iris stroma were quantitatively diminished in the affected inferior iris. Meanwhile, the rate of fundus (retinochoroidal) coloboma in eyes exhibiting dyscoria was remarkably high, although some dyscoric eyes had no fundus coloboma.


CONCLUSIONS
Fatty liver Shionogi mice had iridal coloboma, resulting in inferior corectopia upon light-induced miosis as an indicator of ocular coloboma.
Department of Pathology, Faculty of Pharmaceutical Sciences, Setsunan University, 45-1, Nagaotoge-cho, Hirakata, Osaka 573-0101, Japan. matsuura@pharm.setsunan.ac.jp
Tetsuro
T
Matsuura
Naho
N
Tsuji
Yasushi
Y
Kodama
Isao
I
Narama
Kiyokazu
K
Ozaki
D000818:Animals; D003103:Coloboma / Q000235:genetics / Q000473:pathology*; D005260:Female; D020022:Genetic Predisposition to Disease; D007499:Iris Diseases / Q000235:genetics / Q000473:pathology*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D015877:Miosis