Variation of the axial location of Bruch's membrane opening with age, choroidal thickness, and race

Abstract

Purpose: This study explores variation in the axial location of Bruch's membrane opening (BMO) to determine if this reference plane varies with age and race.

Methods: There were 168 spectral-domain optical coherence tomography (SDOCT) optic nerve head volumes that were obtained from healthy subjects and manually delineated within 24 axial slices to develop point clouds for Bruch's membrane and anterior scleral surfaces. A BMO-independent reference plane was generated based on the peripapillary sclera to measure BMO position. General estimating equations were used to determine the relationship of the axial position of BMO (BMO height) with choroidal thickness, age, and race (African Descent [AD] versus European Descent [ED]) controlling for variations in axial length.

Results: The peripapillary choroid was thinner with increasing axial length (-14.9 μm/mm, P = 0.0096), advancing age (-1.1 μm/y, P = 0.00091), and in the ED group (20.2 μm, P = 0.019) in a multivariable model. Choroidal thickness was also strongly related to BMO height (P < 0.00001) independent of all covariates. Bruch's membrane opening position was more posterior relative to the sclera in older subjects (1.3 μm/y, P = 0.00017), independent of axial length and race. However, when choroidal thickness was included in the model, this association was lost (P = 0.225). There was no significant difference in BMO height between racial groups after adjustment for age and axial length.

Conclusions: Bruch's membrane opening is more posteriorly located in older individuals. These differences are largely due to differences in choroidal thickness and suggest that BMO migrates posteriorly with age due to age-related choroidal thinning. However, additional studies in longitudinal datasets are needed to validate these findings.

Keywords: choriocapillaris; optic nerve head; optical coherence tomography.

Figures

Figure 1

(A) Representative radial section from a compensated SDOCT of the optic nerve head showing the location of placement of the scleral reference plane based on the average position of the scleral between 1700 and 1800 μm from BMO. (B) Principal surfaces delineated and delineation marks within a sample SDOCT radial section. Only Bruch's membrane surface (orange lines and marks) and anterior scleral surface (yellow lines and marks) were used for this study. The region of measurement of choroidal thickness is illustrated and is located 1000 to 1500 μm from BMO. (C) Visualization of complete delineated surfaces. Anterior scleral surface is in yellow and Bruch's membrane is in orange.

Figure 2

Scatterplot and regression line of choroidal thickness and age. Regression line: Choroidal thickness = 288 − 2.11 × age. Slope adjusted for race and axial length = −1.1 μm/y (P = 0.00091).

Figure 3

Scatterplot and regression line BMO height and choroidal thickness. Regression line: BMO Height = −25.1 + 0.53 × choroidal thickness. Slope adjusted for age, race, and axial length = + 0.48 μm/y (P = <0.0001).

Figure 4

Scatterplot and regression line BMO height and age. Regression line: BMO Height = 147 − 1.45 × age. Slope adjusted for axial length and race = −1.3 (P = 0.00017).