Relation Between Refractive Error and Scleral Attenuation Coefficient Obtained from Transscleral OCT Images

Abstract

Purpose : There is evidence that the development of myopia may be associated with changes in scleral biomechanical properties. These changes may affect scleral anatomy and microstructure, and therefore also the scleral scattering properties. The purpose of this study was to determine if there is a relation between refractive error and scleral attenuation coefficient quantified from OCT images.

Methods : The sclera of 23 healthy subjects (range: 16 to 56 y/o) was imaged following an IRB-approved protocol. For each subject, a 10 mm B-scan consisting of 897 A-lines was acquired using a commercial spectral domain OCT system (λ_c = 1325 nm, 2.5 mm axial range, Thorlabs Telesto I, Newton, NJ). A rectangular region of interest (ROI) was identified in the sclera ranging in depth from the episclera - sclera boundary to the sclera-ciliary muscle boundary and ranging laterally from the apex of the ciliary muscle to the episclera. The ROI contained an average of 244 ± 45 A-lines across all subjects and covered an average area of 0.35 ± 0.05 mm (axial) by 0.84 ± 0.15 mm (lateral). The axial intensity profiles in the ROI were averaged. The attenuation coefficient of the sclera was calculated from the slope of the linear fit of the averaged intensity profile. The relation between scleral attenuation coefficient and spherical equivalent refractive error measured using an autorefractor was quantified.

Results : The attenuation coefficient was found to range from 1.37 to 4.84 mm^-1, corresponding to a signal loss ranging from 5.85 to 31.54 dB/mm^-1. The attenuation coefficient was found to be dependent on refractive error (p=0.038).

Conclusions : The results suggest that refractive error is one of the factors that contribute to the variability of the scleral attenuation coefficient.

This is a 2020 Imaging in the Eye Conference abstract.

 

Left: OCT image showing the region of interest (ROI) in the sclera. Right: Average axial intensity profile in the ROI showing the linear fit.

 

Attenuation coefficient of the sclera as a function of refractive error.