Objective To observe the effect of persistent flickering stimulus on the structure and function of retina in guinea pigs during a developmentally sensitive period.Methods Twenty-four two- week-old guinea pigs were randomly divided into flicker light (FL) group and control group, with 12 guinea pigs in each group. Animals in FL group were raised under 500 Lux illumination with a duty diurnal cycle of 50% at a flash rate of 0.5 Hz. Animals in control group were reared under steady 500 Lux illumination. Light emitting diode (LED) lamps were used for lighting under a 12-hour light/12-hour dark cycle. After the collection of fundus photographs and electroretinograms recorded at week 12, eyeballs were taken out, three dimensions were measured, and histopathological changes were examined.Results Compared to control group, tessellated fundus in FL group appeared more prevalent; implicit time of ldquo;ardquo; waves were prolonged in electroretinogram; the eyeballs were increased in horizontal, vertical, axial dimensions by (0.89plusmn;0.30), (0.69plusmn;0.20) and (0.96plusmn;0.30) mm respectively, the differences between two groups were statistically significant (t=12.7,11.9,15.8;P＜0.05). The gap of sclera collagen fiber was slightly widened.The photoreceptor layer was more likely to develop a disordered outer segment, which contained deciduous disc membranes.Conclusion Persistent flickering stimulus is attended by development of excessive ocular enlargement,which could affect the retinal structure and function of photoreceptors.
ObjectiveTo observe the changes of vessel densities (VD) in the macula and optic disc and its correlation with axial length (AL) in pathological myopia (PM). MethodsA retrospective clinical study. A total of 171 eyes from 171 patients admitted to Department of Ophthalmology of Jinshan Hospital of Fudan University from June 2019 to December 2019 were included in this study. Among them, there were 72 males and 99 females; age was 35.0±10.8 years old. The patients were divided into PM group, high myopia (HM) group and non-HM group, 51 cases with 51 eyes, 70 cases with 70 eyes, and 50 cases with 50 eyes, respectively. Optical coherence tomography angiography was used to scan the macular and optic disc areas of all the examined eyes in the range of 6 mm×6 mm. According to the early treatment of diabetic retinopathy study, the 6 mm macular and optic disc scan range was centered on the macular fovea and optic disc, respectively, then divided into two concentric circles with diameters of 1 mm of central area, an annulus between 1-3 mm circles of paracentral area. The paracentral area was divided into superior, inferior, nasal, temporal four quadrants by 2 radiation lines. The VD of superficial capillary plexus (SCP), deep capillary plexus (DCP), outer retina, and choriocapillaris layer were calculated in the central, superior, inferior, nasal, and temporal areas, respectively. The VD of PM, HM and non-HM groups were compared. The variance analysis was used to compare the VD among the three groups; Pearson’s correlation was used to assess the correlation between VD and AL. ResultsThe perifoveal VD of the SCP, outer retina and choriocapillaris layers were all lower in the PM than those of HM and non-HM group, and the differences were statistically significant (P＜0.05). The VD of DCP macular central was higher in the PM than in the HM group, and the difference was statistically significant (P=0.020). In the optic disc, the VD were lower in the PM group than in the non-HM group except for the area of DCP superior, inferior, temporal, outer retinal center, and the differences were statistically significant (P＜0.05). The results of correlation analysis showed that the VD in the DCP macular central, ONH superior and the choriocapillaris ONH central were not correlated with AL (P=0.647, 0.688, 0.146), and the other VDs were negatively correlated with AL (P＜0.05). ConclusionCompared with HM and non-HM groups, the majority of VDs in macular and ONH are lower in participants with PM.