Vascular changes associated with chorioretinal and optic nerve colobomas in rats (Crj: CD(SD), IGS).

OBJECTIVE

Three female adult rats (Crj: CD(SD) IGS) with colobomatous anomalies were investigated.

MATERIALS AND

METHODS

The microvascular changes of the coloboma were studied using the techniques of fluorescein angiography, histology and scanning electron microscopy (SEM) of vascular corrosion casts.

RESULTS

Fluorescein angiography revealed the pits of the optic disk as a dark hole with some abnormalities in vessel arrangement. Light microscopy confirmed the presence of attenuated lamina cribrosa, retinal dysplasia and marked dilation of the retinal veins. SEM revealed that the optic disk coloboma formed a crater-like pit and that central retinal vessels ran a tortuous course along the bottom and side of the crater. Capillaries in the optic nerve head were missing in the affected area. The central retinal veins were thick and had various changes such as strangulation, rough surface structures, mural voids and evaginations, which represent loss of integrity of the vascular wall.

CONCLUSIONS

These vascular changes that are associated with colobomatous anomalies may impede the retinal circulation and be responsible for the fluctuating fluorescein pattern during fluorangiogram of affected animals. The lesions of the vascular wall may increase the subretinal fluid due to the leakage of fluid, thus causing the maculopathy or serous retinopathy, which is frequently associated with posterior pole coloboma.