June 2013
Volume 54, Issue 15
Free
ARVO Annual Meeting Abstract  |   June 2013
1 Changes in Ocular Biometrics and Refraction during Near Work in Downward Gaze over Time
Author Affiliations & Notes
  • Atanu Ghosh
    School of Optometry and Vision Science, Queensland University of Technology, Brisbane, QLD, Australia
  • Michael Collins
    School of Optometry and Vision Science, Queensland University of Technology, Brisbane, QLD, Australia
  • Brett Davis
    School of Optometry and Vision Science, Queensland University of Technology, Brisbane, QLD, Australia
  • Scott Read
    School of Optometry and Vision Science, Queensland University of Technology, Brisbane, QLD, Australia
  • Fan Yi
    School of Optometry and Vision Science, Queensland University of Technology, Brisbane, QLD, Australia
  • Payel Chatterjee
    School of Optometry and Vision Science, Queensland University of Technology, Brisbane, QLD, Australia
  • Footnotes
    Commercial Relationships Atanu Ghosh, None; Michael Collins, None; Brett Davis, None; Scott Read, None; Fan Yi, None; Payel Chatterjee, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science June 2013, Vol.54, 4552. doi:
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      Atanu Ghosh, Michael Collins, Brett Davis, Scott Read, Fan Yi, Payel Chatterjee; 1 Changes in Ocular Biometrics and Refraction during Near Work in Downward Gaze over Time. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4552.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: To investigate changes in the characteristics of the corneal optics, total optics, anterior biometrics and axial length of the eye during a near task, in downward gaze, over 10 min.

Methods: Ten emmetropes (mean - 0.14 ± 0.24 DS) and 10 myopes (mean - 2.26 ± 1.42 DS) aged from 18 to 30 years were recruited. To measure ocular biometrics and corneal topography in downward gaze, an optical biometer (Lenstar LS900) and a rotating Scheimpflug camera (Pentacam HR) were inclined on a custom built, height and tilt adjustable table. The total optics of the eye were measured in downward gaze with binocular fixation using a modified Shack-Hartmann wavefront sensor. Initially, subjects performed a distance viewing task at primary gaze for 10 min to provide a “wash-out” period for prior visual tasks. A distance task (watching video at 6 m) in downward gaze (25°) and a near task (watching video on a portable LCD screen with 2.5 D accommodation demand) in primary gaze and 25°downward gaze were then carried out, each for 10 min in a randomized order. During measurements, in dichoptic view, a Maltese cross was fixated with the right (untested) eye and the instrument’s fixation target was fixated with the subject’s tested left eye. Immediately after (0 min), 5 and 10 min from the commencement of each trial, measurements of ocular parameters were acquired in downward gaze.

Results: Axial length exhibited a significant increase with downward gaze and accommodation over time (p<0.05). The greatest axial elongation was observed in downward gaze with 2.5 D accommodation after 10 min (mean change from baseline 23±3 µm). Downward gaze also caused greater changes in anterior chamber depth (ACD) and lens thickness (LT) with accommodation (ACD mean change -163±12µm at 10 min; LT mean change 173±17 µm at 10 min) compared to primary gaze with accommodation (ACD mean change -138±12µm at 10 min; LT mean change 131±15 µm at 10 min). Both corneal power and total ocular power changed by a small but significant amount with downward gaze (p<0.05), resulting in a myopic shift (~0.10 D) in the spherical power of the eye compared with primary gaze.

Conclusions: The axial length, anterior biometrics and ocular refraction change significantly with accommodation in downward gaze as a function of time. These findings provide new insights into the optical and bio-mechanical changes of the eye during typical near tasks.

Keywords: 677 refractive error development • 605 myopia • 404 accommodation  
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