Abstract
BackgroundThere are few reports regarding the influence of varying illumination on the compensation effect before and after corneal refractive surgery. We aimed to evaluate the changes in refraction, higher-order aberrations, and aberration compensation between mesopic and photopic illumination before and after small incision lenticule extraction.MethodsIn this prospective cohort study, only the right eyes of patients who underwent small incision lenticule extraction for the correction of myopia and myopic astigmatism at the Tianjin Eye Hospital were included. Wavefront refraction and higher-order aberrations were measured preoperatively and 3 months postoperatively under mesopic and photopic illumination. Compensation factors were calculated as 1 − (aberration of the whole eye/aberration of the anterior corneal surface).ResultsForty patients undergoing small incision lenticule extraction were enrolled. All surgeries were completed without postoperative complications. Preoperatively, the eyes only had a statistically significantly higher (t = − 4.589, p < .001) spherical refractive error under mesopic vs. photopic illumination (median [interquartile range], − 6.146 [2.356] vs. − 6.030 [2.619] diopters [D]), whereas postoperatively, the eyes also exhibited statistically significantly higher (t = − 3.013, p = .005) astigmatism (− 0.608 [0.414] vs. − 0.382 [0.319] D). Differences in spherical refraction between the two illuminations were the highest in postoperative eyes (Δ > 0.5 D). Only postoperative eyes exhibited statistically significant elevations (t ≥ 4.081, p < .001) in higher-order aberrations under mesopic illumination, and only preoperative eyes exhibited statistically significantly enhanced (χ2 = 6.373, p = .01 for fourth-order and χ2 = 11.850, p = .001 for primary spherical aberrations) and decreased (χ2 = 13.653, p = .001 for horizontal trefoil) compensation factors under mesopic illumination.ConclusionsExaggerations in higher-order aberrations and myopic shift after small incision lenticule extraction became apparent under mesopic illumination. Slight undercorrection may have an enhanced effect under low illumination and may reduce night vision. The specific changes in compensation effects in preoperative eyes may improve optical quality under mesopic illumination. Postoperative eyes have reduced compensation ability, specifically for spherical aberrations, under mesopic illumination, which may diminish night vision. Further studies that include the measurement of subjective night vision parameters should be conducted.
Highlights
There are few reports regarding the influence of varying illumination on the compensation effect before and after corneal refractive surgery
Exaggerations in higher-order aberrations and myopic shift after small incision lenticule extraction became apparent under mesopic illumination
Previous studies have revealed that higher-order aberrations (HOAs) may increase after refractive surgery, reporting that they are a potential source of poor night vision [3, 4]
Summary
There are few reports regarding the influence of varying illumination on the compensation effect before and after corneal refractive surgery. Previous studies have revealed that higher-order aberrations (HOAs) may increase after refractive surgery, reporting that they are a potential source of poor night vision [3, 4]. Only a few studies have been conducted with the aim of investigating whether night myopia is retained after refractive surgery, or whether varying illumination causes other postoperative changes in refraction. Such studies have generally focused on HOAs. For example, Villa et al [3] reported that secondary astigmatism, coma, and spherical aberrations increased under night vision conditions after laser in situ keratomileusis (LASIK), and that they were statistically significantly correlated with the halo disturbance index. Changes in HOAs do not comprehensively explain changes in optical quality
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