Effects of short‐term exposure to red or near‐infrared light on axial length in young human subjects

• Published in: Ophthalmic & physiological optics Vol. 44; no. 5; pp. 954 - 962
• Main Authors: Swiatczak, Barbara, Schaeffel, Frank
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01.07.2024
• Subjects: Adolescent; Adult; axial length; Axial Length, Eye - diagnostic imaging; Elongation; Female; Humans; infrared light; Infrared Rays - adverse effects; Interferometry - methods; Light - adverse effects; Male; Myopia; Myopia - physiopathology; Phototherapy; red laser light therapy; Refraction, Ocular - physiology; repeated low‐level red light; Young Adult; myopia; red laser light therapy; infrared light; axial length; repeated low‐level red light
• ISSN: 0275-5408; 1475-1313; 1475-1313
• DOI: 10.1111/opo.13311

Purpose To determine whether visible light is needed to elicit axial eye shortening by exposure to long wavelength light. Methods Incoherent narrow‐band red (620 ± 10 nm) or near‐infrared (NIR, 875 ± 30 nm) light was generated by an array of light‐emitting diodes (LEDs) and projected monocularly in 17 myopic and 13 non‐myopic subjects for 10 min. The fellow eye was occluded. Light sources were positioned 50 cm from the eye in a dark room. Axial length (AL) was measured before and after the exposure using low‐coherence interferometry. Results Non‐myopic subjects responded to red light with significant eye shortening, while NIR light induced minor axial elongation (−13.3 ± 17.3 μm vs. +6.5 ± 11.6 μm, respectively, p = 0.005). Only 41% of the myopic subjects responded to red light exposure with a decrease in AL and changes were therefore, on average, not significantly different from those observed with NIR light (+0.2 ± 12.1 μm vs. +1.1 ± 11.2 μm, respectively, p = 0.83). Interestingly, there was a significant correlation between refractive error and induced changes in AL after exposure to NIR light in myopic eyes (r(15) = −0.52, p = 0.03) and induced changes in AL after exposure to red light in non‐myopic eyes (r(11) = 0.62, p = 0.02), with more induced axial elongation with increasing refractive error. Conclusions Incoherent narrow‐band red light at 620 nm induced axial shortening in 77% of non‐myopic and 41% of myopic eyes. NIR light did not induce any significant changes in AL in either refractive group, suggesting that the beneficial effect of red laser light therapy on myopia progression requires visible stimulation and not simply thermal energy.