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Raphaella Hoang Tran, Ashutosh Jnawali, Nimesh Bhikhu Patel, Lisa A Ostrin; Effects of Myopic Defocus on Choroid Thickness in Children and Adults. Invest. Ophthalmol. Vis. Sci. 2019;60(9):4817.
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Recent studies in humans and animal models show that the choroid modulates thickness in response to defocus. Short-term choroid modulation may direct long-term changes in eye growth. This study investigated the effects of myopic defocus on choroid thickness in children and adults using spectral domain optical coherence tomography (SD-OCT).
Subjects, ages 6-45 (n = 30), were enrolled. Experiments took place between 9:00 am and 12:00 pm to minimize effects of diurnal variation. Baseline measurements included biometry (LenStar) and autorefraction (Grand Seiko). Subjects were provided spherical equivalent correction in a trial lens frame. Subjects watched a television at 4 meters for 10 min with distance correction, and two SD-OCT images were collected. Myopic defocus was induced in the non-dominant eye in +1 D steps every to +5D. OCT images were collected and the trial lens was increased by +1D every 10 minutes. The original correction was replaced for another 20 min to assess the recovery. Statistical analysis was completed using 2-factor repeated measures ANOVAs and unpaired T-tests.
For +5D myopic defocus, children (ages 6-17) showed an average increase of 1.7 ± 1.5 µm (mean ± SE) change in central choroid thickness after 50 min. Following removal of the +5D lens, the choroid remained thickened at 1.0 ± 1.9 µm for the 20 min follow up with distance correction. However, subjects ages 18-30 showed an average decrease of -2.9 ± 2.31 µm, and adults ages 31-45 to showed a decrease of -7.7 ± 6.7 µm in central choroid thickness after 50 min. of exposure to myopic defocus.
For adult subjects ages 18-45, the choroid demonstrated thinning, despite exposure to myopic defocus. Choroid thinning at this time of day is in accordance with the natural diurnal rhythms, suggesting that myopic defocus was ineffective at inducing choroidal thickening in adults. On the other hand, children demonstrated approximately 1.7 µm increase in choroid thickness compared to baseline, and approximately 7 µm increase compared to adults, demonstrating a relative thickening of the choroid in children. These results suggest that the choroid in children is more susceptible to thickness modulation by exposure to defocus than in adults, and there may be a “sensitive period” in choroid modulation to visual input.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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