[Fundus hypothermia inhibits retinal damage induced by visible blue light]

We evaluated the role of fundus hypothermia in modifying photic retinopathy. The fundus was cooled with a copper plate inserted behind the eyeball. The anterior end of the plate was chilled with dry ice. Retinal temperature was thus reduced to 30 and 33 degrees C. This cooling manipulation had no effect on body temperature, retinochoroidal architecture, or choroidal circulation. The fundus was then exposed to visible blue light at an irradiance of 8 mW/cm2 for one hour. Retinal damage developed in 9 out of 10 eyes after the exposure alone, and in 3 out of 10 eyes when retinal temperature was reduced to 30 degrees C. The incidence of light damage with the cooling manipulation was decreased significantly when compared to that of controls (p < 0.05). Contrary to this, 5 out of 5 retinas treated with hypothermia at 33 degrees C showed damage and there was no significant difference in the incidence from that of controls. This finding indicates that local hypothermia at 30 degrees C protects the retina from light damage and that a subtle temperature milieu plays a role in producing retinal damage.