Adaptive Illuminance Effects on Retinal Morphology and Refraction: A Comprehensive Study of Night Myopia

<bold>Background: </bold>We aimed to study the optical and retinal modifications that occur after adapting to different lighting conditions including photopic, mesopic, scotopic, blue light and red light conditions.<bold>Methods: </bold>Thirty young healthy subjects with a mean age of 23.57 +/- 3.45 years were involved in the study (both eyes included). They underwent aberrometry and optical coherence tomography at both the central and peripheral retina with the 3 x 3 mm(2) macular cube protocol before starting adaptation to the illuminations (baseline) and after remaining for 5 min under the five different lighting conditions inside a controlled lighting cabinet.<bold>Results: </bold>Significant myopization (p = 0.002) was observed under scotopic and mesopic lighting conditions, while hypermetropization occurred under the influence of blue LED light. In the central retina, a significant thickening of the inner temporal (p = 0.025) and outer inferior (p = 0.021) areas was observed in the scotopic area, and the thickening increased even more under blue and red light. The mean central thickness decreased significantly under photopic lighting conditions (p = 0.038). There was an increase in the mean volume of the central retinal area with red light and a reduction in the volume under photopic lighting (p = 0.039). In the peripheral retina, no significant thickness changes were observed after adapting to any of the lighting conditions (p > 0.05). Regarding morphological changes, a significant increase in retinal eccentricity (p = 0.045) and the shape factor (p = 0.036) was found. In addition, a significant correlation was found only between the eccentricity and volume of the central retina in scotopic conditions (r = -0.265; p = 0.041), meaning that a higher volume was associated with lower retinal eccentricity.<bold>Conclusions: </bold>When exposed to different lighting conditions, the retina changes in shape, and ocular refraction is modified to adapt to each condition, revealing the phenomenon of night myopia when transitioning from photopic to scotopic regimes.