Sunday, October 27, 2024
10/27/2024
PROJECT SUMMARY Myopia is a global public health problem affecting over two billion people worldwide. Concerns for myopia are increasing because axial eye elongation associated with myopia is a major risk factor for several sight- threatening ocular pathologies in later life. Although optical methods based on a single visual cue—peripheral myopic defocus—have shown some potential to slow eye growth, the partial effectiveness of these methods suggests that the peripheral defocus cue alone is not sufficient to effectively restrain eye growth and myopia progression. The emmetropization mechanism also uses wavelength cues (from longitudinal chromatic aberration in broad-band light) to modulate eye growth, with an in-focus light serving as a stop signal. The wavelength cues appear more powerful than the defocus cues because they can cause the emmetropization mechanism to essentially ignore the refractive state. However, the potential of using wavelength cues to slow eye growth and myopia progression has yet to be systemically studied. In near-primates and primates, narrow- band red light (peak wavelength 636 ± 10 nm), which does not stimulate the short-wavelength sensitive cones, acts as a powerful anti-myopia stimulus, producing hyperopia and counteracting negative lens-induced myopia. Even brief periods of exposure a day produce substantial hyperopia, suggesting a temporal non-linearity of the effect that makes it feasible for clinical translation. We have recently found that exposure to amber light (wavelengths > 500 nm) also produces the same hyperopic effect in tree shrews with similar potency to red light. Unlike red filters, amber filters only minimally reduce ambient illumination and allow sufficient brightness even in typical indoor lighting conditions. The Gawne and Norton model hypothesized that longer wavelength light that avoids the stimulation of short-wavelength sensitive cones produces an image contrast that the emmetropization mechanism interprets as the eye being too long and signals to slow its growth. We aim to test this hypothesis by asking whether daily periods of amber light exposure slow eye growth and myopia progression in children in a pilot, “proof-of-concept” study. The specific aim is to determine the efficacy of amber contact lens wear for up to four hours a day in slowing myopia progression and axial elongation. We will recruit 40 myopic children aged 8 to <13 years, have them wear daily disposable, amber- tinted soft contact lenses for up to four hours daily, and measure refractive error and axial length for a year. By comparing the outcomes to the published one-year results from children wearing daily disposable single-vision and dual-focus soft contact lenses, we aim to determine whether a wavelength cue, amber light, slows childhood myopia progression and how its efficacy compares to that of the dual-focus lenses. This project will provide pilot efficacy data and potentially lead to a placebo-controlled, randomized clinical trial of a novel, wavelength-based myopia control strategy, providing an entirely new avenue for childhood myopia control.
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