Difference In Spherical Refraction Research Articles

Effects of varying illumination on ocular aberrations and aberration compensation before and after small incision Lenticule extraction: a prospective cohort study

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.

Overestimation of hyperopia with autorefraction compared with retinoscopy under cycloplegia in school-age children

AimTo compare sphere and cylinder refraction values using retinoscopy and autorefraction under cycloplegic conditions in children.MethodsThis cross-sectional study was carried out using multistage cluster sampling. The target population was children...

Comparison of objective refraction in darkness to cycloplegic refraction: a pilot study

BackgroundThe aim was to assess non‐cycloplegic objective refraction in darkness using an open‐field auto‐refractor, and furthermore to compare it with distance cycloplegic subjective refraction and distance cycloplegic retinoscopy in the light, in children and young adults.MethodsTwenty‐three, visually‐normal, young‐adults (46 eyes) ages 23 to 31 years, and five children (10 eyes) ages five to 12 years, participated in the study. The spherical component of their refraction ranged from −2.25 D to +3.75 D with a mean of +1.80 D, and a mean cylinder of −0.70 D. Three techniques were used to assess refractive error. An objective measure of the non‐cycloplegic refractive state was obtained using an open‐field autorefractor (WAM‐5500) after five minutes in the dark to allow for dissipation of accommodative transients and relaxation of accommodation. In addition, both distance retinoscopy and subjective distance refraction were performed following cycloplegia (Cyclopentolate, 1%) using conventional clinical procedures. All measurements were obtained on the same day within a single session. The spherical component of the refraction was compared among the three techniques in both the children and adults.ResultsThere was no significant difference in spherical refraction among the three techniques: non‐cycloplegic objective refraction in the dark, distance cycloplegic retinoscopy and distance cycloplegic subjective refraction, in either the adults [F(2, 137) = 0.79, p = 0.45] or the children [F(2, 27) = 0.47, p = 0.62]. Mean difference in the spherical component between refraction in the dark and the cycloplegic distance retinoscopy was −0.34 D (r = 0.89) in the adults and +0.14 D (r = 0.96) in the children. The mean difference in spherical component between refraction in the dark and the cycloplegic distance subjective refraction was −0.25 D (r = 0.92) in the adults and −0.05 D (r = 0.95) in the children.ConclusionComparison of the spherical refractive component between the three techniques was not significantly different and furthermore, they were highly correlated in both the children and adults in this pilot study. Non‐cycloplegic refraction in the dark may provide a reliable adjunct or alternative to conventional cycloplegic refraction in both children and young adults.

Comparison of Subjective Refraction under Binocular and Monocular Conditions in Myopic Subjects.

To compare subjective refraction under binocular and monocular conditions, and to investigate the clinical factors affecting the difference in spherical refraction between the two conditions. We examined thirty eyes of 30 healthy subjects. Binocular and monocular refraction without cycloplegia was measured through circular polarizing lenses in both eyes, using the Landolt-C chart of the 3D visual function trainer-ORTe. Stepwise multiple regression analysis was used to assess the relations among several pairs of variables and the difference in spherical refraction in binocular and monocular conditions. Subjective spherical refraction in the monocular condition was significantly more myopic than that in the binocular condition (p < 0.001), whereas no significant differences were seen in subjective cylindrical refraction (p = 0.99). The explanatory variable relevant to the difference in spherical refraction between binocular and monocular conditions was the binocular spherical refraction (p = 0.032, partial regression coefficient B = 0.029) (adjusted R2 = 0.230). No significant correlation was seen with other clinical factors. Subjective spherical refraction in the monocular condition was significantly more myopic than that in the binocular condition. Eyes with higher degrees of myopia are more predisposed to show the large difference in spherical refraction between these two conditions.

Monochromatic aberrations in children and youth in different cycloplegic conditions

AbstractPurpose The aim of the study was to quantify low and high order Zernike aberrations in children and youths as well as to investigate influence of fogging and cycloplegia on the refraction and aberrations measurement.Methods KR‐1W Topcon aberrometer was used to measure aberrations in refractometer and aberrometer mode. Children were examined three times. First examination in whole group was performed after fogging stimulus used once ‐ in first of three continuous measurements, second after fogging stimulus performed for each measurement and third after pharmacological cycloplegia with 1% Tropicamid. Second and third measurements were performed in selected group of children. Totally 556 schoolchildren and 74 young sportsmen aged from 6‐to‐18 years were investigated. Average age was 13.87, SD 2.29 in large group and 11.33 years, SD 2.7 in smaller group.Results We found significant differences in spherical refraction measured after pharmacological cycloplegia compared to that after fogging. Refraction after cycloplegia was more hyperopic. There were higher differences in high hyperopic children. There were no differences between fogging and cycloplegic measurements in myopes higher then ‐2.00 D.. Aberrometry has given more myopic results then refractometry. Cylinder values were almost the same. Keratometer readings were the same in all measurements conditions. We found similar levels of high order aberrations in myopic, emmetropic and hyperopic children. There was no noticeable symmetry in high order aberrations between right and left eye.Conclusion Both methods of low order aberrations measurement are similar. Optical parameters of cornea do not depend on the cycloplegic status. Low order Zernike aberrations strictly correspond to the refraction error.