Quantify retinal structure in high-altitude residents with and without High altitude polycythemia

Abstract

Background To assess retinal structural parameters in high-altitude (HA) residents with and without high altitude polycythemia (HAPC) and to elucidate the relationship between retinal structural parameters and hemoglobin (HGB). Methods This cross-sectional study included 55 HAPC patients and 52 healthy HA residents. Retinal structural parameters including retinal nerve fiber layer (RNFL) thickness, optic nerve head (ONH) parameters and retinal vessels diameter were acquired from spectral domain optical coherence tomography (SD-OCT) and ImageJ software, and compared between HAPC group versus healthy HA group. The associations between retinal parameters and HGB were assessed by Pearson correlation analyses. Results In comparison of HAPC group versus healthy HA group, RNFL thickness was significant thicker in the nasal quadrant of the optic disc in HAPC group (74.82 ± 14.4 VS. 66.06 ± 13.71µm, P = 0.002). Bigger rim area, bigger disc area and bigger cup volume were also observed in HAPC group (all P < 0.05). Moreover, retinal venous diameters (RVD) of all four quadrants dilated significantly (all P < 0.05) and retinal arterial diameters (RAD) dilated only in superior nasal quadrant in HAPC group (0.08 ± 0.01 VS. 0.07 ± 0.01mm, P = 0.002). No associations between HGB and retinal parameters were found (all P > 0.05). Conclusions long-term HA exposure secondary HAPC could result in slightly thickened RNFL, enlarged ONH and dilated retinal veins. However, increased blood viscosity caused by HAPC should not be responsible for those changes. This study deepens the understanding of the impact of HA environment on retina.