Relationship of Geographic Altitude with Foveal Avascular Zone Metrics and Vascular Density Values Assessed by OCT Angiography.

PURPOSE: To evaluate variations in vascular density (VD) and foveal avascular zone (FAZ) metrics in relation to geographic altitude in healthy subjects from 6 Latin American cities. DESIGN: Cross-sectional study. PARTICIPANTS: Healthy volunteers from 6 Latin American cities. METHODS: One hundred eighty-five volunteers were recruited over a 3-month period. The RTVue-XR Avanti system (Optovue, Inc, Fremont, CA) was used along with split-spectrum amplitude-decorrelation angiography (SSADA) software 7.1 to obtain OCT angiography (OCTA) images from fovea-centered 3 × 3-mm2 and 6 × 6-mm2 angioscans for both the superficial and deep capillary plexuses (SCP and DCP, respectively). FAZ measurements were performed in a full retina slab based on the full retina vasculature using OCT angiograms. Analyses of variance were performed for all variables, and P < 0.05 indicated statistical significance. MAIN OUTCOME MEASURES: Retinal SCP and DCP VD; FAZ area, perimeter, and parafoveal density at 300 µm (FD-300). RESULTS: Three hundred seventy eyes of 185 participants (71 males and 114 females; mean age, 39.09±15.06 years; age range, 20-80 years) were assessed. The mean VD in the SCP and DCP was 46.94% (±3.11%) and 52.48% (±3.14%), respectively, with 3 × 3-mm2 scans and 50.62% (±3.13%) and 52.87% (±5.5%), respectively, with 6 × 6-mm2 scans. Mean FAZ area, perimeter, and FD-300 were 0.31 (± 0.11 mm2), 2.18 (± 0.43 mm), and 51.44 (± 3.64%), respectively. Mean SCP VD values in 3 × 3-mm2 scans were significantly higher and lower in La Paz and Lima, respectively, compared to those in the other cities (P = 0.001). VD in the 6 × 6 mm2 SCP scans, the DCP (all scans), and FAZ metrics showed no significant differences. CONCLUSIONS: VD showed a direct relationship with geographic altitude in SCP 3 × 3-mm2 scans in this group of healthy Hispanic volunteers. These findings indicate that geographic altitude should be accounted for when performing retinal OCTA evaluation of VD values.

Evaluation of VEGF gene polymorphisms and proliferative diabetic retinopathy in Mexican population.

AIM: To assess if the included vascular endothelial growth factor (VEGF) polymorphisms rs3025035, rs3025021 and rs2010963 are associated to proliferative retinopathy in a Mexican population with type 2 diabetes mellitus (T2DM). METHODS: A case-control study was conducted in adult individuals with T2DM associated to proliferative retinopathy or non-proliferative retinopathy from Oct. 2014 to Jun. 2015 from the Retina Department of the Asociation to Prevent Blindness in Mexico. The selected patients were adults with a diagnosis of T2DM ≥5y. All subjects had a comprehensive ocular examination and the classification of the retinopathy severity was made considering the Early Treatment Diabetic Retinopathy Study (ETDRS) standardization protocols. Genomic DNA was extracted from whole fresh blood. All samples were genotyped by qPCR for selected VEGF polymorphisms. Hardy-Weinberg equilibrium was calculated by comparing Chi-square values between the expected and the observed values for genotype counts. RESULTS: In total 142 individuals were enrolled, 71 individuals with T2DM and associated proliferative retinopathy and 71 individuals with non-proliferative retinopathy. One-sided Fisher's exact test was performed for rs3025021 [OR (95% CI)=0.44(0.08-2.2); P=0.25] and rs2010963 [OR (95% CI)=0.63(0.25-1.6); P=0.23]. The minor allelic frequencies obtained were 26% for rs3025021, 10% for rs3025035 and 61% for rs2010963. The pairwise linkage disequilibrium between the three SNP was assessed, and was as follows: rs3025021 vs rs3025035: D'=1.0, r2=0.1043, P≤0.0001; rs3025021 vs rs2010963: D'=0.442, r2=0.0446, P=0.149; rs3025035 vs rs2010963: D'=0.505, r2=0.0214, P=0.142. CONCLUSION: This is the first analysis involving VEGF polymorphisms and proliferative diabetic retinopathy in a Mexican population. A major finding of the present study is that none of the polymorphisms studied was significantly associated with proliferative retinopathy. Based on these results, we can infer that different populations have different associations for the same polymorphisms.