Choroidal Thickness in Myopic Children in the BLINK Study

Abstract

Purpose : The Bifocal Lenses In Nearsighted Kids (BLINK) Study is a three-year, multi-center, randomized clinical trial evaluating the efficacy of multifocal soft contact lenses for myopia control. We describe choroidal thickness and cross-sectional area in this large cohort of myopic children prior to randomization to a contact lens treatment arm.

Methods : Spectral-domain optical coherence tomography (SD-OCT) star scans (30° B-scans; 6 meridians) of the right eye of 281 myopic children enrolled in the BLINK Study were acquired prior to the commencement of study contact lens wear. B-scans were collected using enhanced depth imaging (EDI) and were cropped by 100 pixels per side as a pre-processing step to eliminate most of the optic nerve and edge artifacts, reducing each scan to 26°. The retinal pigmented epithelium/choroidal boundary and choroidal/scleral boundary were segmented using previously validated semi-automated routines utilizing graph theory and dynamic programming. Choroidal thickness and cross-sectional area were calculated from the segmented images. The relationship between choroidal thickness and both refractive error and axial length were determined.

Results : The mean age (± SD) and spherical equivalent refractive error as measured by cycloplegic autorefraction were 10.3 ± 1.2 years (range: 7-11 years) and -2.41 ± 1.01 D (range: -0.82 to -5.48 D), respectively. The mean axial length as measured by optical biometry was 24.49 ± 0.81 mm (range: 22.65 to 26.79 mm), and 60% of subjects were female. Mean sub-foveal choroidal thickness was 303 ± 58 µm (range: 177 to 529 µm). The mean choroidal area averaged across the six B-scans (26°) was 2.25 ± 0.40 mm². The choroid was generally thicker inferior to the fovea than superior to the fovea and thinnest near the optic nerve (Figure 1). Thinner sub-foveal choroidal thickness was associated with more myopic refractive errors (β = 9 µm/diopter; p=0.01) and longer axial lengths (β = -11 µm/mm axial length; p=0.01).

Conclusions : In these myopic children, choroidal thickness was correlated with both refractive error and axial length, as expected. Choroidal thickness measurements are being collected annually in the BLINK Study and will be used in the future to evaluate whether choroidal thickness is associated with the progression of myopia.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 

Figure 1: Mean baseline choroidal thickness of all myopic children (n = 281) prior to randomization in the BLINK Study