Axial Elongation Associated with Biomechanical Factors during Near Work

作者：Ghosh Atanu^*; Collins Michael J; Read Scott A; Davis Brett A; Chatterjee Payel

来源：Optometry and Vision Science, 2014, 91(3): 322-329.

DOI：10.1097/OPX.0000000000000166

• near work
• myopia
• accommodation
• axial length
• downward gaze

Purpose To investigate the changes occurring in the axial length, choroidal thickness, and anterior biometrics of the eye during a 10-minute near task performed in downward gaze. %26lt;br%26gt;Methods Twenty young adult subjects (10 emmetropes and 10 myopes) participated in this study. To measure ocular biometrics in downward gaze, an optical biometer was inclined on a custom-built height- and tilt-adjustable table. Baseline measures were collected after each subject performed a distance primary gaze control task for 10 minutes to provide washout period for previous visual tasks before each of three different accommodation/gaze conditions. These other three conditions included a near task (2.5 diopters [D]) in primary gaze and a near (2.5 D) and a far (0 D) accommodative task in downward gaze (25 degrees), all for 10 minutes%26apos; duration. Immediately after and then 5 and 10 minutes from the commencement of each trial, measurements of ocular biometrics (e.g., anterior biometrics, axial length, choroidal thickness, and retinal thickness) were obtained. %26lt;br%26gt;Results Axial length increased with accommodation and was significantly greater for downward gaze with accommodation (mean SD change, 23 +/- 13 m at 10 minutes) compared with primary gaze with accommodation (8 +/- 15 m at 10 minutes) (p %26lt; 0.05). A small amount of choroidal thinning was also found during accommodation that was statistically significant in downward gaze (13 +/- 14 m at 10 minutes; p %26lt; 0.05). Accommodation in downward gaze also caused greater changes in anterior chamber depth and lens thickness compared with accommodation in primary gaze. %26lt;br%26gt;Conclusions Axial length, choroidal thickness, and anterior eye biometrics change significantly during accommodation in downward gaze as a function of time. These changes seem to be caused by the combined influence of biomechanical factors (i.e., extraocular muscle forces, ciliary muscle contraction) associated with near tasks in downward gaze.

• 出版日期2014-3