Abstract
Purpose :
To determine whether coherent and visible long wavelength light is needed to elicit axial eye shortening for myopia therapy.
Methods :
Incoherent narrow-band red (620±10 nm) or near-infrared (NIR, 875±30 nm) light with similar power per retinal unit area (red: 0.33 mW/mm2, NIR: 0.44 mW/mm2, calculated for a pupil size of 5 mm) was provided by light-emitting diodes (LED) and projected on one eye in sixteen myopic (average spherical equivalent refraction (SE) -3.6±1.4 D) and fourteen non-myopic (average SE -0.2±0.5 D) subjects for 10 minutes. Fellow eyes were covered with an eye patch. Light sources were positioned at 50 cm distance from the eyes in a dark room, causing a calculated retinal image light patch with a diameter of 0.87 mm. Axial length was measured before and after exposure by low-coherence interferometry (Lenstar, Haag Streit, with auto-positioning system).
Results :
Non-myopic subjects responded to red light with significant eye shortening, while NIR light induced minor axial elongation (-12.9±16.7µm vs. +5.5±11.7 µm, respectively, difference p<0.01). Only 43% of the myopic subjects responded to red light exposure with a decrease in axial length and changes were therefore, on average, not significantly different from changes observed with NIR light (+0.7±12.4 µm vs. +1.3±11.5 µm, respectively, n.s). Interestingly, there was a significant correlation between spherical equivalent refractive error and induced changes in axial length after exposure to NIR light, in both myopic and non-myopic eyes (r(14)=0.52, r(11)=0.67, respectively, both p<0.05), with IR-light inducing more axial elongation with increasing myopia. Such a correlation was not observed after exposure to red light, neither in myopic nor non-myopic subjects.
Conclusions :
Incoherent narrow-band red light at 620 nm induces eye shortening after 10 minutes in 78% of non-myopic and 43% of myopic eyes. Near-infrared light did not induce any significant changes in axial length in either refractive group, suggesting that the beneficial effect of red laser light therapy on myopia progression requires visual stimulation and not simply thermal energy.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.