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Xiaoying Zhu, Peter Yoon, Gulnoza Azieva, Stephen Dellostritto, Victor Lin, Amy Pope, David Troilo, Ana Nour, Alexandra Benavente-Perez; Short periods of darkness may reduce compensation for experimentally-imposed defocus in marmosets. Invest. Ophthalmol. Vis. Sci. 2019;60(9):4811. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Studying the temporal integration of visual signals is crucial to understanding how time spent on different visual tasks can affect emmetropization and refractive error development. We previously studied the effects of briefly interrupting contact lens imposed myopic or hyperopic defocus in marmosets by removing the lenses. In this preliminary study we assessed the effect of interrupting lens-imposed defocus with comparably brief periods of darkness.
Thirty marmosets were treated monocularly with +5D or -5D soft contact lenses for 4 wks from 10 wks of age. In the continuous treatment group, marmosets wore either a +5D (n=8) or –5D (n=13) lens for 9 hrs/day. In the interrupted treatment group, lens-wear was interrupted by 30 mins of darkness twice/day (+5D, n=5; –5D, n=4). On-axis refractive error (RE) and vitreous chamber depth (VC) were measured using an autorefractor and high frequency A-scan biometry at baseline and after 4 wks of treatment.
Wearing lenses continuously significantly changed RE and growth rates in the treated eys (relative change in RE: +5D, +1.9 ± 1.0 D, –5D, –1.9 ± 0.5 D, p<0.05; relative change in VC growth rate: +5D: –0.7 ± 0.4 μm/day, –5D: +3.9 ± 0.8 μm/day, p<0.01). Although not statistically significant, interrupting positive lens wear with periods of darkness appears to reduce compensation for imposed myopia by preventing reduced eye growth (+5D continuous vs. interrupted: RE: +1.9 ± 1.0 D vs. +1.0 ± 0.5 D, p=0.40; VC: –0.7 ± 0.4 µm/day vs. +0.7 ± 0.8 μm/day, p=0.08). Interrupting negative lens wear appears to reduce compensation for imposed hyperopia by reducing eye growth (–5 D continuous vs. interrupted: RE: –1.9 ± 0.5 D vs. 0.0 ± 0.3 D, p<0.05; growth rates: +3.9 ± 0.8 μm/day vs. +1.1 ± 0.9 μm/day, p=0.10).
Similar to interrupting positive and negative lens wear with brief periods of vision, interrupting lens wear with brief periods of darkenss, although not statistically significant for all compariosns, appears to reduce compensation for imposed defocus. Additional animals are being tested to increase statistical power to fully test this hypothesis. If confirmed in this primate model, these results would be similar to those described in other species, supporting the existence of non-linear temporal integration of the visual signal, which may have clinical implications for myopia control in school-aged children.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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