Manual segmentation of choroidal volume in emmetropic and high myopic eyes

Abstract

Purpose: To compare choroidal volume between emmetropic and high myopic eyes and to assess the variations of choroidal volume among eyes with non-pathologic high myopia, pathologic high myopia with vitreoretinal pathology and choroidal neovascularization (CNV)

Methods: We retrospectively reviewed imaging studies of 137 eyes of 86 patients who underwent choroidal volume measurement using enhanced depth imaging (EDI)-OCT. Forty four eyes were emmetropic (axial length: ≥ 23.5 mm and < 24.5 mm) and 93 eyes were high myopic (axial length: > 26.5 mm). High myopic eyes were divided into high myopia without pathology (51 eyes), high myopia with vitreoretinal pathology (30 eyes), and high myopia with CNV (12 eyes). The EDI-OCT protocol used to assess the choroidal volume consisted in 31 high-resolution B-scans centered on the fovea. The choroid was segmented manually from the hyper-reflective line of the retinal pigment epithelium to the chorio-scleral junction on SD-OCT by two retina specialists. Choroidal volume map and measurements were obtained applying the 6-mm diameter grid used by the Early Treatment Diabetic Retinopathy Study (ETDRS).

Results: Mean subfoveal and total choroidal volume were 0.24 ± 0.07 mm3 and 7.67 ± 2.15 mm3 in emmetropic eyes, 0.16 ± 0.06 mm3 and 5.60 ± 1.77 mm3 in high myopic eyes without pathology, 0.08 ± 0.04 mm3 and 3.01 ± 1.26 mm3 in high myopic eyes with vitreoretinal pathology, 0.09 ± 0.05 mm3 and 3.29 ± 1.41 mm3 in high myopic eyes with CNV. After adjusting for age and sex, subfoveal and total choroidal volume were lower in high myopic eyes without pathology than emmetropic eyes (both P<0.0001). Subfoveal and total choroidal volume were lower in high myopia with vitreoretinal pathology and high myopia with CNV than high myopia without pathology (both P<0.01) after adjusting for age, sex, and axial length. Among the 4 ETDRS quadrants, superior quadrant had the greatest choroidal volume in emmetropia (2.07 ± 0.71 mm3) and high myopia without pathology (1.54 ± 0.62 mm3), while the nasal quadrant had the lowest choroidal volume in emmetropia (1.62 ± 0.69 mm3) and high myopia without pathology (1.08 ± 0.59 mm3).

Conclusions: We concluded that the choroid is thinner in high myopic eyes than emmetropic eyes, but eyes with coexisting myopic pathology have more severe thinning.

Keywords: 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • 452 choroid • 605 myopia