Abstract:

Objective To investigate the changes in retinal structure and microcirculation in the patients with high myopia （HM） and the non-HM individuals， and to elucidate the correlations between axial length （AL） and the related parameters. Methods A total of 80 eyes from 40 patients with simple HM （non-pathological myopia） were enrolled as case group， while 80 eyes from 40 age- and sex-matched non-HM subjects were selected as control group. The best-corrected visual acuity （BCVA），AL，spherical equivalent （SE）， and optical coherence tomography angiography （OCTA） examination were performed in all the subjects. OCTA examination was used to measure the vascular density of the superficial retinal capillary plexus （SCP）， deep retinal capillary plexus （DCP）， and radial peripapillary capillary （RPC）， as well as central macular thickness （CMT）， and the area and volume of the foveal avascular zone （FAZ） of the subjects in two groups. The differences in these parameters of the subjects between two groups were analyzed. The AL of the subjects in two groups was measured using a biometer， and its correlations with the parameters mentioned above were evaluated. Results No statistically significant differences were observed in age or sex distribution between two groups （P>0.05）. Compared with control group， both SCP and DCP vessel densities acrossing the whole （excluding the foveal）， parafoveal， and perifoveal regions of the macular retina of the patients in case group were significantly decreased （P<0.05）. Compared with control group， the RPC vessel densities in the optic disc region of the patients in case group were significantly decreased in the whole， peripapillary， peripapillary superior， and peripapillary inferior sectors （P<0.001）， while the RPC vessel density was increased inside the disc （P<0.01）. Compared with control group， the whole FAZ volume of the patients in case group was increased （P<0.01）， while the parafoveal and perifoveal CMT were decreased（P<0.001）. In case group， AL was negatively correlated with SCP vessel density （r=-0.642， P<0.001）， DCP vessel density （r=-0.388， P<0.001）， RPC vessel density （r=-0.639， P<0.001）， and CMT （r=-0.495， P<0.001）， but positively correlated with FAZ volume （r=0.580， P<0.001）； no significant correlation was found between AL and FAZ area （r=-0.062， P=0.587）. Conclusion The patients with HM may exhibit early reductions in SCP， DCP， and RPC vessel densities， thinning of the central retina， and increased FAZ volume. Furthermore， as AL increases， SCP， DCP， and RPC vessel densitiesas as well as CMT decreases， while FAZ volume increases， suggesting significant associations between AL and the parameters mentioned above.

Key words: High myopia, Retinal capillary, Foveal avascular zone, Axial length, Optical coherence tomography angiography