Purchase this article with an account.
Thomas T Norton, Alexander H Ward, Timothy J Gawne; Long-wavelength (red) Light Produces Hyperopia in Juvenile and Adolescent Tree Shrews. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5525.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Exposure to long-wavelength light produces a very hyperopic refractive state and slowed axial elongation in infant tree shrews when eyes are approaching emmetropia from hyperopia (Gawne et al., Program No. 59.09 2014 Neuroscience Meeting Planner). We asked if red light produces hyperopia in juvenile and adolescent tree shrews that have completed their initial emmetropization.
Tree shrews were raised by their mothers in fluorescent colony lighting (F34CW RS WM ECO, 100-300 lux) on a 14:10 h schedule until they began 12-16 days of red-light treatment at 35 (n = 5) or 95 (n = 3) days of visual experience (DVE, days after eye opening). An array of LEDs (624 or 636 ± 10 nm) atop the cage in an otherwise dark room provided illuminance on the floor of the cage of 500-1100 human lux. Non-cycloplegic refractive state was measured daily. At the end of treatment, the 95 DVE group was re-measured with tropicamide cycloplegia. Ocular component dimensions were measured at the start and end of red-light treatment. Animals returned to colony lighting and the refractive state was followed for up to 20 days. These groups were compared with a group of normal animals (n=7) and with a previous group that began red-light treatment at 11 DVE.
During red-light treatment (see figure), the refractive state of animals in both groups became significantly hyperopic compared to their pre-treatment refraction and to age-matched normal animals. The hyperopic shift in the group that began treatment at 35 DVE was (mean ± SEM) 2.1 ± 0.9 diopters (D); the shift in the 95 DVE group was 2.4 ± 0.4 D. Both were smaller than the 5.5 D hyperopic shift found in a group that began red-light treatment at 11 DVE. In the 35 DVE group, the vitreous chamber was signficantly smaller (2.61 ± 0.19 mm vs. 2.74 ± 0.21 mm) and the choroid signficantly thicker (72 ± 3 µm vs. 56 ± 2 µm) than in normal animals. Upon return to colony lighting, refractions decreased toward normal levels. One animal in the 95 DVE group exposed to 500 human lux red, recovered in 1100 lux colony lighting despite the increased illuminance.
Light that only activates long-wavelength sensitive cones causes hyperopia even in juvenile and adolescent tree shrews by slowing axial elongation and increasing choroid thickness. In contrast, plus-lens wear is effective in producing hyperopia only in infant tree shrews (Siegwart & Norton, Exp Eye Res 2010, 91:660).
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
This PDF is available to Subscribers Only