Abstract
Purpose :
To study the retinal capillary microvasculature and the choriocapillaris(CC) in myopic eyes using swept-source optical coherence tomography angiography(SS-OCTA).
Methods :
Patients with high myopia(≥-6D; axial length≥26.5mm), moderate myopia(≥-3D,<-6D), and age-matched healthy subjects were enrolled in this prospective study. Any subjects with pathologic macular abnormalities were excluded. SS-OCTA was performed using a Zeiss PLEX Elite instrument with a 6×6mm scan pattern centered on the fovea. Two repeated volume scans were acquired for image averaging. The instrument pre-defined en-face slab of the superficial and deep retinal capillary microvasculature was used. A slab spanning from 21-31µm deep to the RPE fit line was used to isolate the CC. The OCTA images were exported for averaging using Image J. Littmann’s method and the Bennett formula were applied to adjust for magnification impact in the high and moderate myopia groups. The resultant images were then binarized. Vessel density(VD) and vessel length density(VLD) of the superficial and deep retinal capillary plexus(SCP,DCP) and CC flow deficit(FD) were compared between three groups.
Results :
Thirty-three eyes of 20 patients with high myopia, 36 eyes of 21 patients with moderate myopia, and 33 eyes of 24 normal controls were included. The VD of the SCP was lower in the high myopia group compared with the moderate myopia and control groups(p<0.05), but the VD of the DCP demonstrated no significant difference among the three groups(p>0.05). The VLD of both the SCP and DCP were lower in the high and moderate myopia groups compared with the control group(p<0.05). The CC FD% in the high myopia group(25.55±2.30) was significantly greater than both the control(23.99±2.67) and moderate myopia(24.14±3.33) groups(p<0.05). Of note, the severity of the CC FD was not correlated with choroidal thickness(p>0.05).
Conclusions :
The retinal microvasculature may demonstrate alterations in highly myopia eyes. The CC in macular regions shows greater impairment in eyes with high myopia compared with eyes with lesser degrees of myopia, and these deficits are already present in the absence of pathologic or degenerative myopia. The threshold of CC FD leading to myopic maculopathy remains to be defined.
This is a 2020 ARVO Annual Meeting abstract.