Abstract
Purpose :
To quantitatively characterise alterations in posterior eyewall morphology in highly myopic eyes in different directions of gaze.
Methods :
A prospective study was performed on 106 highly myopic eyes. Ultrasound scans were acquired in primary, up, downward, nasal, and temporal gaze. A validated intensity-based segmentation algorithm was used to quantify the posterior eyewall geometry on digitalised B-scan images. Posterior eyewall local curvature (K) and distance (L) to the transducer were calculated. The associations between directions of gaze, axial length (AL), and presence of staphyloma with the K and L parameters were assessed.
Results :
Eccentric gaze was often independently associated with the various K and L parameters after accounting for longer AL and presence of staphyloma. Specifically, downward gaze was associated with increased posterior eyewall concavity as reflected in the KMax (maximum degree of the spatial change in curvature of entire posterior eyewall): β=0.050, p<0.001, and absolute value of KMax: β=0.041, p=0.011. Both downward gaze and upgaze were independently associated with an increase in the derivative of absolute KMax (that is consistent with more apparent, steeper staphyloma ridges), local KMax (that detects KMax at smaller intervals), and Kstd (that represents likelihood of staphyloma presence), and a decrease in LMax (that represents movement of the staphyloma apex), with all p<0.05. The beta coefficients for downward gaze were consistently greater in magnitude compared with those in upgaze. After accounting for AL and presence of staphyloma, horizontal gaze was independently associated only with decrease in Lstd (that also represents likelihood of staphyloma presence) and LMax.
Conclusions :
Downward gaze, compared to other directions of gaze, results in the greatest posterior eyewall deformation in highly myopic eyes. These findings are consistent with and may provide supportive structural evidence for the association between near work, which involves downward gaze, with myopia development and progression. Further studies are required to evaluate these associations.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.