The correlation between intraocular pressure and choroidal microcirculation in patients with high myopia

Abstract

Background: High myopia (HM) is a leading cause of visual impairment worldwide and the choroid plays a key role in HM progression. Intraocular pressure (IOP) may also be involved in HM development, while the relationship between IOP and choroidal microcirculation in HM patients remains poorly characterized. Purpose: To investigate the correlation between IOP and choroidal microcirculation in HM individuals using swept-source optical coherence tomography angiography (SS-OCTA). Methods: This cross-sectional observational study enrolled 118 eyes of 118 participants aged 18-30, comprising 64 HM eyes (axial lengths (AL) ≥ 26mm) and 54 mild-to-moderate myopic (MM) eyes (AL < 26 mm). Data on spherical equivalent (SE), AL and central corneal thickness (CCT) were collected. IOP was measured using a non-contact tonometer (NCT) and corrected with a formula to minimize the effect of CCT. Based on ETDRS classification, choroidal thickness (ChT) and vascular parameters including choriocapillaris layer vessel density (ChCVD), choroidal vascular index (CVI), choroidal vascular volume (CVV), choroidal stromal volume (CSV) and choroidal stromal density (CSI) were calculated from SS-OCTA. Results: In this cohort, HM eyes exhibited higher corrected IOP (P < 0.05) and lower ChT, CVV and CSV across all grids compared to MM eyes (P < 0.001). Increased CSI and decreased CVI were also observed in most sectors of the HM eyes (P < 0.05). After adjusting for age, gender and AL, corrected IOP was correlated with SE, ChT, CVI and CSI in the subfoveal central and inner nasal grids among HM patients (P < 0.05). No significant correlation was found between AL and corrected IOP (P > 0.05). Conclusion: In our population, compared to MM eyes, HM eyes showed higher IOP levels, which were negatively correlated with SE but not AL. Additionally, elevated IOP was observed to be associated with reduced choroidal thickness and vascularity in specific macular regions. The potential link between IOP and choroidal microcirculation may be involved in HM progression.

Keywords: choroidal thickness; choroidal vascularity; high myopia; intraocular pressure; swept-source optical coherence tomography angiography.

Figure 1

Representative OCTA images of choroid. (A) Representative macular images under En-face mode by OCTA. (A1) The distance from the Bruch's membrane to the lower boundary of the choroid is defined as ChT; (A2) ChT in ETDRS grids. (B) Representative choroidal vascular images by OCTA. (B1) OCTA images of ChC; (B2) OCTA images of ChV; (B3) Illustration of ChCVD.

Figure 2

Illustration of choroidal vascularity analysis. CVI. (B) CSI. (C) CVV. (D) CSV.

Figure 3

The workflow of participant selection for the study.

Figure 4

Comparison of mean ChT and choroidal vascular parameters in different ETDRS grid sectors. (A) Comparison of mean ChT in different ETDRS grids between HM group and MM group. (B) Comparison of ChCVD in a radius of 6 mm of the macular region between HM group and MM group. (C) Comparison of mean CVI in different ETDRS grids between HM group and MM group. (D) Comparison of mean CVV in different ETDRS grids between HM group and MM group. (E) Comparison of mean CSV in different ETDRS grids between HM group and MM group. (F) Comparison of mean CSI in different ETDRS grids between HM group and MM group.