Scanning laser ophthalmoscopy and optical coherence tomography imaging of spectacular ecdysis in the corn snake (Pantherophis guttatus) and the California king snake (Lampropeltis getulus californiae).

PURPOSE: One of the singularities of the eyes of snakes is the presence of the spectacle, a transparent and vascularized integument covering the cornea. The spectacle is completely renewed during ecdysis. Combined scanning laser ophthalmoscopy (SLO), optical coherence tomography (OCT), and conventional macrophotography were used to image this phenomenon. MATERIAL AND METHODS: A spectral OCT/SLO examination and macrophotography were performed in four healthy adult corn snakes (Pantherophis guttatus) and one healthy adult California king snake (Lampropeltis getulus californiae) the day before the start of ecdysis and then daily during ecdysis. RESULTS: In all animals, ecdysis lasted 5 days. The spectacle was hardly visible at baseline, but became obvious at day one, while the subspectacular space became larger and the superficial cornea presented a hyperechoic band. At day two, eye surface became translucent, and at the same time, vascularization of the spectacle was visible using SLO. At day 3, the vascularization was no longer visible, while the subspectacular space increased and the eye surface remained translucent. At day 4, the eye surface was transparent and the superficial hyperechoic band started to become less bright. At day 5, the old spectacle was shed and all the parameters returned to baseline. CONCLUSION: We hypothesize that the echogenicity modifications of the anterior cornea correspond to major metabolic activity associated with new spectacle formation. This increased metabolic activity may contribute to the neovascularization and play an important role in the accumulation of fluid in the subspectacular space, facilitating the shedding of the old spectacle.

Effect of mydriasis induced by topical instillations of 0.5% tropicamide on the anterior segment in normotensive dogs using ultrasound biomicroscopy.

OBJECTIVE: To determine the effect of 0.5% tropicamide and the resultant mydriasis on the anterior segment in normotensive dogs using ultrasound biomicroscopy. PROCEDURE: Twenty-four dogs without ocular disease underwent ultrasound biomicroscopic examination of both the eyes under general anesthesia. Pharmacologic mydriasis was induced in the right eye of each dog by the topical instillation of 0.5% tropicamide. Ultrasound biomicroscopic examinations were performed and the anatomical parameters of the anterior segment were evaluated including the geometric iridocorneal angle (ICA) - formed by the plane of the iris root and the internal corneoscleral limbus - the width of the opening of the ciliary cleft (CC), the width of the mid-CC, the length of the CC, and the anterior chamber (AC) depth (distance between the corneal endothelium and the anterior lens capsule). RESULTS: Mydriasis resulting from the topical use of 0.5% tropicamide is associated with an increase in the geometric ICA and a decrease in the opening of the CC, without any effect on the width of the mid-CC, or on the length of the CC, or on the AC depth. CONCLUSIONS: Mydriasis induced by topical 0.5% tropicamide results in modification of the anterior segment which may influence the drainage of aqueous humor.