Choroidal volume variations with age, axial length, and sex in healthy subjects: a three-dimensional analysis

Abstract

Purpose: To demonstrate the 3-dimensional choroidal volume distribution in healthy subjects using enhanced depth imaging (EDI) spectral-domain optical coherence tomography (SD-OCT) and to evaluate its association with age, sex, and axial length.

Design: Retrospective case series.

Participants: A total of 176 eyes from 114 subjects with no retinal or choroidal disease.

Methods: The EDI SD-OCT imaging studies of healthy patients who had undergone a 31-raster scanning protocol on a commercial SD-OCT device were reviewed. Manual segmentation of the choroid was performed by 2 retinal specialists. A macular choroidal volume map and 3-dimensional topography were automatically created by the built-in software of the device. Mean choroidal volume was calculated for each Early Treatment Diabetic Retinopathy Study (ETDRS) subfield. Regression analyses were used to evaluate the correlation between macular choroidal volume and age, sex, and axial length.

Main outcome measures: Three-dimensional topography and ETDRS-style volume map of the choroid.

Results: Three-dimensional topography of the choroid and volume map was obtained in all cases. The mean choroidal volume was 0.228 ± 0.077 mm(3) for the center ring and 7.374 ± 2.181 mm(3) for the total ETDRS grid. The nasal quadrant showed the lowest choroidal volume, and the superior quadrant showed the highest choroidal volume. The temporal and inferior quadrants did not show different choroidal volume values. Choroidal volume in all the EDTRS rings was significantly correlated with axial length after adjustment for age (P < 0.0001), age after adjustment for axial length (P < 0.0001), and sex after adjustment for axial length (P < 0.05). Choroidal volume decreases by 0.54 mm(3) (7.32%) for every decade and by 0.56 mm(3) (7.59%) for every millimeter of axial length. Male subjects have a 7.37% greater choroidal volume compared with that of female subjects.

Conclusions: Enhanced depth imaging SD-OCT is a noninvasive and well-tolerated procedure with an excellent ability to visualize 3-dimensional topography of the choroid and to measure choroidal volume at the posterior pole using manual segmentation. Age and axial length are inversely correlated with choroidal volume, most likely leading to changes in retinal metabolic support in elderly, highly myopic patients. Sexual differences should be considered when interpreting an EDI SD-OCT scan of the choroid.

Financial disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Figure 1

Example of enhanced depth imaging of the choroid on a horizontal B-scan passing through the fovea in a left eye, before (A) and after (B) manual segmentation. The basement membrane of the retinal pigment epithelium (inner border of the choroid) appeared as a regular hyper-reflective line, with a concave aspect towards the choroid. Differently, the chorio-scleral interface (outer border of the choroid) appeared irregular and corrugated, following the course of the deepest choroidal vessels.

Figure 2

A three-dimensional topographic visualization of the choroid with superimposed color-coded choroidal thickness map (microns) in an eye with axial length of 23.2 mm (A–D) and in an eye with axial length of 26.5 mm (E–H). The superior quadrant of the macula appears thicker than the other quadrants, while the nasal quadrant is the thinnest.

Figure 3

Effect of age (A–C) and axial length (D–F) on color-coded choroidal thickness map and mean choroidal volume of each subfield of the Early Treatment Diabetic Retinopathy Study (ETDRS) grid. (A) Right eye of a 30 years old patient: total choroidal volume is 8.53 mm³; (B) Right eye of a 50 years old patient: total choroidal volume is 7.39 mm³; (C) Right eye of a 70 years old patient: total choroidal volume is 6.36 mm³; (D) Hyperopic eye (axial length = 22.5 mm): total choroidal volume is 8.61 mm³; (E) Emmetropic eye (axial length = 24.5 mm): total choroidal volume is 7.47 mm³; (F) Myopic eye (axial length = 26.5 mm): total choroidal volume is 6.54 mm³.

Figure 4

Left: scatterplot of axial length (AXL) and macular choroidal volume of all subjects shows a significant negative correlation (P<0.01; R²=0.122). Right: scatterplot of age and macular choroidal volume of all subjects shows a significant negative correlation (P<0.01; R²=0.150).