Objective To investigate the protective effect of recombinant erythropoietin (EPO) on the photoreceptor cells in rat with retinal detachment (RD).Methods One hundred and sixtytwo normal male rats were randomly divided into normal control (NC) group, RD model group, RD+phosphate buffer solution （RD+PBS） group, RD+EPO 100 ng group, RD+EPO 200 ng group and RD+EPO 400 ng group. Three days after RD, activated caspase3 and bclXL were detected by Western blot and/or immunofluorescence, and apoptosis were measured by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate digoxigenin nick-end labeling（TUNEL）. Fourteen and 28 days and two months after RD, the outer nuclear layer （ONL）thickness was measured by histopathologic method.Results Western bolt indicated that the protein level of activated caspase-3 and bcl-XL between six groups were statistically significant（F=35.96, 30.75；P＜0.01）. The number of TUNEL positive cells and activated caspase-3 positive cells are consistent with each other in different groups. Fourteen days and two months after RD，the differences of ONL thickness between six groups were statistically significant（F=21.52，96.25；P＜0.01）.Conclusion Supplement of EPO after RD can alleviate apoptosis by inhibiting of the caspase-3 activity and increasing the expression of bcl-XL,thus exerts protective effect on photoreceptor cells.
Objective To observe the distribution of human photoreceptor cells at the posterior pole, detect the change of density of the cells affected by eccentricity, and analyze the relationship between the density distribution and the visual sensitivity. Methods Twenty human eye cups with the cornea removed were fixed in 4% polyformaldehyde for 1-4 weeks, and the retinal mounts were observed by differential interference contrast microscope to reveal the retinal cellular configuration and density. The inner segments of photoreceptor cells were first observed from the center to the temporal peripheral part of the retinal mounts. Results The highest density of visual cone cells was at the central fovea (134 000-267 000/mm2, mean 198 090/mm2; CV value:18.2%). The density and individual variation decreased rapidly in the peripheral area. The high density area of rod cells was at the 4 mm of the eccentricity, with the highest value of 72 610-182 350/mm2 and with the high density between 3 and 5 mm. Conclusions The inner segment of photoreceptor cells was monolayer, which may tell the cellular absolute value. The high density of retinal cone cells at the central fovea provide the basis of sensitive central visual acuity, which relates to the individual variation and development. The rod cells have the peak density at the eccentricity with 4 mm, and this area has the greatest sensitivity of dim vision.