Funduscopic morphology of the light- and dark-adapted eye of the toadfish (Opsanus tau) in vivo

Abstract

Intraocular funduscopy and photography permitted serial examination and documentation of time-related changes in the living toadfish (Opsanus tau) eye as it went from the dark-adapted to the light-adapted state. In the present study, the fully dark-adapted eye showed virtually no choroidal, pigment epithelial, or retinal vascular detail. The optic nerve was chalky white with indistinct borders. Grayish brown to chalky white retinal streaks radiated from the optic nerve into the periphery. As light adaptation began, the retinal streaks faded, with the retinal vasculature and the underlying choroidal and pigment epithelial detail becoming more discernible. Once the eye became fully light adapted, the typical geographic orange and black mottled appearance of the underlying pigment epithelium and choroid was visible, and the optic nerve head developed a pink hue with a distinct border. Even in the fully light-adapted eye, a vague radiation of lines could be seen extending from the optic nerve. This was superimposed on a cross-hatched mosaic of black dots seen throughout the fundus, not visible in the fully dark-adapted eye. Histological examination of the retina indicated forward migration of pigment in the pigment epithelium in the light-adapted state.