Although vascular endothelial growth factor (VEGF) is a primary mediator of retinal angiogenesis, VEGF inhibition alone is insufficient to prevent retinal neovascularization. Hence, it is postulated that there are other potent ischemia-induced angiogenic factors. Erythropoietin possesses angiogenic activity, but its potential role in ocular angiogenesis is not established. We measured both erythropoietin and VEGF levels in the vitreous fluid of 144 patients with the use of radioimmunoassay and enzyme-linked immunosorbent assay. Vitreous proliferative potential was measured according to the growth of retinal endothelial cells in vitro and with soluble erythropoietin receptor. In addition, a murine model of ischemia-induced retinal neovascularization was used to evaluate erythropoietin expression and regulation in vivo. The median vitreous erythropoietin level in 73 patients with proliferative diabetic retinopathy was significantly higher than that in 71 patients without diabetes (464.0 vs. 36.5 mIU per milliliter, P<0.001). The median VEGF level in patients with retinopathy was also significantly higher than that in patients without diabetes (345.0 vs. 3.9 pg per milliliter, P<0.001). Multivariate logistic-regression analyses indicated that erythropoietin and VEGF were independently associated with proliferative diabetic retinopathy and that erythropoietin was more strongly associated with the presence of proliferative diabetic retinopathy than was VEGF. Erythropoietin and VEGF gene-expression levels are up-regulated in the murine ischemic retina, and the blockade of erythropoietin inhibits retinal neovascularization in vivo and endothelial-cell proliferation in the vitreous of patients with diabetic retinopathy in vitro. Our data suggest that erythropoietin is a potent ischemia-induced angiogenic factor that acts independently of VEGF during retinal angiogenesis in proliferative diabetic retinopathy.

Purpose.: To investigate the relationship between the cystoid spaces in the outer plexiform layer (OPL) and the characteristics of the photoreceptors beneath the cystoid spaces in patients with diabetic macular edema (DME). Methods.: In this observational cross-sectional study, 123 eyes of 96 consecutive patients with clinically significant macular edema were retrospectively reviewed. The characteristics of the photoreceptors on optical coherence tomography (OCT) images represented by the external limiting membrane (ELM) and the junction between inner and outer segments (IS/OS), and their association with the overlying cystoid spaces were investigated. Results.: The areas beneath the cystoid spaces in the OPL had a longer transverse length of disrupted or faint IS/OS and disrupted ELM lines than those without cystoid spaces (P < 0.001, P < 0.001, and P = 0.009). The IS/OS lines beneath the cystoid spaces had higher reflectivity than those in areas without cystoid spaces (P < 0.001). Enlarged cystoid spaces extending from the inner nuclear layer to the OPL were associated with disrupted IS/OS or ELM but not faint IS/OS (P < 0.001, P < 0.001, and P = 0.467). The transverse length of disrupted IS/OS at the fovea was correlated with the logarithm of the minimum angle of resolution (logMAR) more than the association between foveal thickness and logMAR (r = 0.49, P < 0.001 vs. r = 0.28, P = 0.002). The ELM descended to the RPE more frequently in eyes with single-lobulated fluorescein pooling in the foveal avascular zone than those with multi-lobulated pooling (P < 0.001). Conclusions.: OCT showed that the cystoid spaces in the OPL were accompanied by photoreceptor damage beneath the cystoid spaces in DME.

Aim: To study the correlation between integrity of the photoreceptor layer after resolution of macular oedema (MO) associated with branch retinal vein occlusion (BRVO) and final visual acuity (VA), and to determine prognostic factors for visual outcome. Methods: We retrospectively studied 46 eyes from 46 patients with resolved MO secondary to BRVO, the foveal thickness of which was less than 250 µm at final observation. We assessed the status of the third high reflectance band (HRB) in the fovea using optical coherence tomography (OCT) at final observation, and studied OCT images taken at the initial visit in the hope of identifying a factor that would be prognostic of visual outcome. Results: No differences were found in initial VA or in foveal thickness between eyes with or without complete third HRB at final observation. However, final VA in eyes without a complete HRB was significantly poorer (p<0.002). Additionally, initial status of the third HRB in the parafoveal area of unaffected retina was associated with final VA; lack of visualisation of the third HRB at 500 µm (p = 0.0104) or 1000 µm (p = 0.0167) from the fovea on initial OCT images was associated with poor visual recovery after resolution of the MO. Conclusion: Integrity of the photoreceptor layer in the fovea is associated with VA in resolved MO, and status of the third HRB before treatment might be predictive of visual outcome.

Optical coherence tomography (OCT) has enabled objective measurement of the total retinal thickness in diabetic macular edema (DME). The central retinal thickness is correlated modestly with visual impairment and changes paradoxically after treatments compared to the visual acuity. This suggests the clinical relevance of the central retinal thickness in DME and the presence of other factors that affect visual disturbance. Recent advances in spectral-domain (SD) OCT have provided better delineation of the structural changes and fine lesions in the individual retinal layers. Cystoid spaces in the inner nuclear layer and outer plexiform layer are related to quantitative and qualitative parameters in fluorescein angiography. OCT often shows vitreoretinal interface abnormalities in eyes with sponge-like retinal swelling. Serous retinal detachment is sometimes accompanied by hyperreflective foci in the subretinal fluid, which exacerbates the pathogenesis at the interface of the photoreceptors and retinal pigment epithelium. Photoreceptor damage at the fovea is thought to be represented by disruption of the external limiting membrane or the junction between the inner and outer segment lines and is correlated with visual impairment. Hyperreflective foci in the outer retinal layers on SD-OCT images, another marker of visual disturbance, are associated with foveal photoreceptor damage.