Objective To observe the changes of photopic negative response (PhNR) of electroretinography (ERG) in patients with retinal vein occlusion (RVO). Methods A total of 30 patients (30 eyes) with retinal vein occlusion (RVO) diagnosed by indirect ophthalmoscopy and fundus fluorescein angiography (FFA) were selected; the unaffected fellow eyes of the patients and another 25 healthy agematched individuals (50 eyes) were cllected as the normal control. All of the patients underwent the examination of visual acuity, visual field, and flashERG (FERG); the normal control ones underwent FERG. In the 30 patients with RVO, there were 14 with central RVO (CRVO) and 16 with branch RVO (BRVO). According to the disease history and results of FFA, the patients were divided into 3 time groups: lt;1 month, 1-3 months, and gt;3 months; according to the types of RVO, the patients were divided into ischemic and nonischemic group. The amplitude of PhNR and other parameters were analysed. The relationship among the amplitude of PhNR and RVO types and time course were analyzed.Results The amplitude of PhNR in the CRVO and BRVO eyes was (28.20plusmn;5.8) and (36.96plusmn;4.71) mu;V, respectively; those in the unaffected fellow and control eyes was (61.25plusmn;3.93) and (59.33plusmn;16.92) mu;V, respectively; the amplitude of PhNR was significantly smaller in the CRVO and BRVO eyes than those in the unaffected fellow or control eyes (F=10.69 and 9.80，P＜0.001; F=9.69 and 9.75，P＜0.001). The amplitude of PhNR in ischemic and nonischemic group in CRVO eyes was (22.77plusmn;15.73) and (36.63plusmn;12.91) mu;V, respectively; the difference between the two groups was significant（t=6.54, Plt;0.01）. The amplitude of PhNR in ischemic and nonischemic group in BRVO eyes was (32.39plusmn;13.22) and (46.73plusmn;10.43) mu;V, respectively; there was no significant difference between the two groups（t=2.12, Plt;0.05）. The amplitude of PhNR was (24.58plusmn;14.60) and (27.94plusmn;15.73) mu;V, respectively, in CRVO and BRVO eyes with lt; 1 month disease course; was (50.39plusmn;13.80) and (58.69plusmn;12.43) mu;V in those with 1-3 months disease course; and was (25.40plusmn;19.94) and (34.48plusmn;16.72) mu;V in those with ＞3 months diseases course. Significant difference was found between the 1-3 months group and ＞3 months group in CRVO eyes（F=4.30，Plt;0.01）. Conclusions The amplitude of PhNRs was significantly smaller in RVO eyes than those in the unaffected fellow or control eyes.The amplitude of PhNR amplitude of ischemic type was smaller than that of nonischemic type. The amplitude of PhNR has descending，ascending，and descending tendency during the disease courses.
Objective To explore the connection between the melanin content of retinal pigment epithelial (RPE) cells and the function of photoreceptors, and the function of melanin on retinal light damage. Methods Agematched old dopachrome tautomerase knockout (DCT-/-) mice and wildtype mice were collected as the DCT-/- group and wildtype group, with 20 mice in each group. Baseline electroretinograms (ERG) in accordance with the international standards for the clinical electrophysiology were performed on all the mice, and the max ERG was recorded. Two mice were randomly selected in each group and were executed，and the removal eyeballs were as the control. The remaining 18 mice in each group were exposed to cold fluorescent light with the quantity of electricity of 20 W for 36 hours with a circle of 12 hours light12 hours dark12 hours light, which was repeated continuously for three times. The light intensity was (5000plusmn;356) lx. Six days after the light illumination, ERG were performed again and the results were recorded. Cervical dislocation methods were used to executed 2 mice which were chosen randomly in each group, and the eyeballs were removed. The tissue sections were observed under the optical and electron microscope.Results The results of ERG showed that the amplitude of a and b wave was lower in DCT-/- group than that in wildtype group before and after light injury （a wave before light injury: t=-7.13，Plt;0.01；b wave before light injury: t=-4.414，Plt;0.01；a wave after light injury: t=-10.162，Plt;0.01；b waveafter light injury: t=-6.772，Plt;0.01）. The decrease of amplitude of a and b wave was much obvious in DCT-/- group than that in wildtype group （a wave:t=4.975,Plt;0.01；b wave:t=2.908,Plt;0.01）. After the light injury, retinal edema and thinning were found in DCT-/- group which wasobvious than that in wildtype group; the photoreceptor layers and melanin were more seriously affected in DCT-/- group than that in wild-type group.Conclusions After the light illumination, the melanin of RPE cells reduces and the function of photoreceptors decreases, which suggests that melanin may play an protective role in the light injury.