Objective To explore the protective mechanism and effect of coenzyme Q10 on the retinal photic injury in experimental rats. Methods Thirty Sprague-Dawley rats were divided randomly into 3 groups: normal control group, positive control group, and coenzyme Q10 group. The experimental model of photic injury in rats was established by being exposed to intense green fluorescent light with an illuminance level of (2000plusmn;120) Lux for 24 hours. The physiological saline and coenzyme Q10 were given through tail intravenous injection at 24 hours and 30 min before light exposure in positive control group and coenzyme Q10 group, respectively. Ophthalmectomy was performed 1 day after the illumination. Changes of retinal histopathology and ultrastructure were observed by light and electron microscope. The apoptosis rate of retinal cells was detected by flow cytometry. Results The result of histopathological examination showed that in coenzyme Q10 group, the outer segments arranged trimly with only few cell apoptosis; the inner and outer segments slightly swelled, and compared with the positive group, the histopathological changes alleviated obviously. The result of flow cytometry revealed that the apoptosis rate of retinal cells was (1.65plusmn;1.48)% in normal control group, (25.83plusmn;2.92)% in positive control group, and (12.43plusmn;2.25)% in coenzyme Q10 group, respectively. The apoptosis rate of retinal cells was higher in positive control group than that in the normal control group (t=18.28, Plt;0.01), and lower in coenzyme Q10 group than that in the positive control group (t=9.07, Plt;0.01). Conclusion Coenzyme Q10 plays an important role in preventing the photic injury of retina and optic cell apoptosis. (Chin J Ocul Fundus Dis, 2007, 23: 122-125)