CONICET | Buscador de Institutos y Recursos Humanos

Glaucoma is a leading cause of blindness worldwide, characterized by specific visual field defects due to the loss of retinal ganglion cells and damage to the optic nerve head. Elevated intraocular pressure (IOP) is one of the most important risk factors for development of glaucoma. We have developed an experimental model of glaucoma in rats through the chronic (once/week) injection of hyaluronic acid (HA) in the anterior chamber of the eye. Recent evidences indicate that a population of retinal ganglion cells is intrinsically photosensitive (through the expression of a specific fotopigment, melanopsin), and transmits light information regulating several non-visual processes, like synchronization of the biological clock and pupil light reflex. The aim of this work was to study the effect of ocular hypertension induced by HA on the levels of melanopsin (assessed by Western blot), pupil light reflex, and expression of cfos (by immunohistochemistry) in retinal ganglion cells induced by a light pulse (600 lux,10 min). HA was injected in one eye and vehicle in the contralateral eye, once a week, during 10 weeks. In a group of animals, the injections of HA or vehicle were performed bilaterally. The results indicate that melanopsin levels and pupil contraction velocity was significantly lower in eyes injected with HA with respect to controls (p<0.01). The immunohistochemical study indicated that light-induced expression of cFOS in retinal ganglion cells significantly decreased in HA injected eyes. These results indicate that chronic ocular hypertension induces a significant functional deficit of retinal ganglion cells. Taken into account the involvement of photosensitive ganglion cells in the synchronization of circadian rhythms, these results could suggest a significant relationship between glaucoma and the circadian physiology.