In the Rd mouse, which carries a cGMP phosphodiesterase β-subunit (βPDE) mutation, the opsin-promoted expression of βPDE promotes photoreceptor survival and induces a twofold increase in light sensitivity.34 Lentiviral HIV-mediated βPDE delivery in newborn Rd mice prevents photoreceptor degeneration for up to 24 weeks.35 The Royal College of Surgeons (RCS) rat is another well-characterised retinal degeneration model in which the RPE fails to phagocytise shed photoreceptor outer segments, and photoreceptor loss results. These studies have lead to reduced suffering and provided clues to treatments that are now helping patients live more productive lives. Following resolution of ulcerative keratitis, sectoral peripheral superficial corneal gray opacification, vascularization, and pigmentation slowly migrated centripetally to the axial cornea of both eyes. The defect was successfully repaired using deep lamellar keratectomy and application of a tectonic graft, using glycerin-preserved canine corneal stroma. Both cyclosporine and tacrolimus are effective in increasing the STT in dogs naïve to lacrimostimulants but tacrolimus should only be used as a second-line agent for short-term and intermittent use due to its carcinogenic properties. Tectonic corneal grafting is usually performed with fresh or frozen cornea3, 5, 6, 15. Occasionally the eye will have a bluish appearance.
Corneal dystrophy is the most common cause of lipid deposition in the canine cornea.