Abstract
Purpose :
To examine the effects of narrow-band, long-wavelength (red) ambient light on the maintenance of emmetropization, lens-induced myopia and form-deprivation myopia in juvenile tree shrews.
Methods :
Seventeen tree shrews (Tupaia belangeri) were reared in red light (14-hr red, 10-hr dark; peak wavelength = 634 nm, half bandwidth = 9µm; ~600 lux on cage floor) from 24 to 35 days of visual experience either without visual treatment (Binocular Red Controls, n = 7), with concurrent monocular -5D lens (Red -5D, n = 5), or monocular diffuser treatment (Red FD, n = 5). Non-cycloplegic refractions and ocular dimensions were measured in awake animals using an autorefractor and an optical biometer, respectively. Data were compared with those obtained from animals previously reared in colony “white” light without visual treatment (Colony Controls, n = 7), with concurrent monocular -5D lens (Colony -5D, n = 5) or monocular diffuser (Colony FD, n = 10).
Results :
Red light produced relative hyperopia in the Binocular Red Controls (closed red circles in both panels. Averaged refraction, Red-Controls vs. Colony-Controls: +3.0 ± 0.7D vs. +1.0 ± 0.4D) and in the untreated eyes of the lens-rearing subjects (panel A: Red -5D vs. Colony -5D, +2.5 ± 0.5D vs. +1.3 ± 0.3D; panel B: Red FD vs. Colony FD, +2.4 ± 0.3D vs. +1.0 ± 0.2D). The hyperopia in the untreated eyes of the Red -5 D and Red FD groups occurred with a two-day delay compared with the Binocular Red Controls and remained about 1 D less hyperopic. Red light slowed the myopic changes in the treated eyes of the Red -5D and Red FD subjects and reduced the final degree of myopia (Red -5D vs. Colony -5D, -1.1 ± 0.9D vs.-3.8 ± 0.3D, p < 0.05; Red FD vs. Colony FD, -0.3 ± 0.6D vs. -5.4 ± 0.7D, p < 0.05). The degree of lens-induced myopia (treated – untreated eyes, -3.6 ± 0.4D vs. +5.1 ± 0.2D of Colony -5D) and form-deprivation myopia (Red FD vs. Colony FD, -2.7 ± 0.4D vs. -6.4 ± 0.6D) were also reduced (p < 0.05). The refractive changes were inversely correlated with the changes in vitreous chamber depth (r = -0.91, p < 0.05).
Conclusions :
For tree shrews, red light slowed ocular growth and caused hyperopic shifts not only in eyes that had previously attained a near-emmetropic refractive state (Gawne et al., 2017), but also in minus-lens-treated eyes and diffuser-treated eyes.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.