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Alexander Hadwyn Ward, Thomas T Norton, Timothy Gawne; Interaction of minus-lens wear and form deprivation with long-wavelength light in tree shrews. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2745.
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Long-wavelength (red) narrow-band ambient light that only activates the long-wavelength sensitive (LWS) cones produces hyperopia in infant tree shrews, a diurnal mammal closely related to primates (Gawne et al. Soc. Neurosci, 2014 abstract 59.09). The purpose of this study was to ask how minus-lens wear or form deprivation, which produce myopia in colony lighting, would interact with the red-induced hyperopia.
At 11 days of visual experience (DVE), tree shrews were placed in ambient red light (628 ± 10 nm, approximately 1000 human lux) on a 14 hour/10 hour light/dark cycle. At the start of red-light exposure, animals began to wear a monocular –5 D lens (–5 D red, n=5) or diffuser (FD red, FD colony, n=5). The untreated fellow eye served as a red-light treated control. Refractions of the FD red group (average of both eyes) were compared with a group with FD in colony lighting. Refractions in the –5 D red group were compared with normal animals (n=7). Red light treatment continued 13 days (–5 D red) or 23 days (FD red). Refractive state was measured daily in awake animals with an autorefractor in dim light (red or colony).
The control eyes of the –5 D lens-treated animals (Fig. 1A) became substantially hyperopic (6.0 ± 1.0 D, mean ± SEM) compared with normal eyes (0.8 ± 0.1 D). The –5 D-red treated eyes became myopic and stabilized at –2.6 ± 1.4 D. The relative myopia (lens treated vs. “control” eyes) was –8.6 ± 0.6 D. For comparison, eyes that wore a monocular –5 D lens in colony lighting (Norton et al. 2010) became myopic (–3.6 ± 0.3 D). The control eyes of the FD red group (Fig. 1B) became hyperopic (4.0 ± 1.4 D) compared to the colony FD control eyes (2.2 ± 0.4 D) but were not as hyperopic as those of binocular-red animals (7.0 ± 0.7 D, Gawne et al. 2014). The FD-red treated eyes had a similar amount of myopia (–5.0 ± 1.0 D) as the FD colony eyes (–4.3 ± 1.3 D).
When images are present (–5 D red animals), the control eyes became hyperopic. The lens caused a myopic shift (lens compensation) that stabilized, but was larger (relative to control eye) than occurs in colony lighting. Both wavelength and refractive cues were used. The myopic response in FD shows that the red-induced hyperopia in control eyes depends on the presence of images on the retina. These results suggest that the emmetropization mechanism uses multiple cues in guiding refractive development.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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