42.2 Material and Methods

42.2.1 Animal

Animals were cared for and handled according to the Association for Research in Vision and Ophthalmology (ARVO) statement for the use of animals in vision and ophthalmic research, with the University of Oklahoma Faculty of Medicine guidelines for use of animals in research. Thirty two SD rats, which weighed 250– 350 g, were randomly assigned to one of eight groups: untreated control group, LED control group, six light-induced damage groups and in them three with LEDprotection. All animals were born and raised in a 12-h-on and 12-h-off bright cyclic light environment.

42.2.2 Light Damage

Four cages were placed in a light box and each rat was housed separately in individual chambers to prevent them from shielding each other from the light. The rats, which were neither dilated nor anesthetized, were exposed to constant light for 3 h of different illuminations of 900, 1,800 and 2,700 lux, respectively. Then the rats were put back into the animal room with the cyclic light for 5 days, ant then into a dark room overnight for the Electroretinograms examination.

42.2.3 670 nm LED Treatment

GaAIAs LED arrays of 670-nm wavelength (LED) bandwidth 25–30 nm at 50% power were obtained from Quan-tum Devices. Rats were anesthetized with a ketamine-xylazine mixture. The LED array was positioned directly over the animal heads at a distance of 1 in. Treatment was consisted of irradiation at 670 nm for 30 min resulting in a power intensity of 50 mW/cm2 and an energy density of 90 J/cm. The LED treatment was done 3 h before the light damage and 0, 24 and 48 h after the light damage.

42.2.4Evaluation of Photoreceptor Cell Function by Electroretinography

The SD rats were kept in total darkness overnight before ERG recording. Animals were anesthetized with a ketamine-xylazine mixture. Pupils were dilated with 1.0% tropicamide and 2.5% phenylephrine HCl. A circular silver wire, recording electrode, was positioned on the cornea, a reference electrode was positioned on the mouth, and a ground electrode was placed on one foot (Cao et al. 2001). The duration of white-light stimulation was 10 ms with a 60-s delay between flashes at seven