Purpose
To characterize age- and sex-related changes in corneal refractive parameters in myopic and hyperopic patients undergoing refractive surgery.
Design
A retrospective cross-sectional study.
Methods
Analysis of demographic and refractive parameters of myopic and hyperopic patients who underwent laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) between January 2000 and December 2014 at the Care-Vision Laser Centers, Tel-Aviv, Israel.
Results
A total of 62,422 eyes of 31,211 patients were included. With advancing age, refractive surgery was performed for lower magnitudes of myopia and hyperopia. The magnitude of cylinder was higher in men than in women in both myopic and hyperopic patients. In comparison, women were significantly more myopic than men (spherical equivalent of −3.73 diopter [D] versus −4.07 D; P < 0.01). The myopic group sphere (r = 0.044; P < 0.001) had a positive correlation with age, whereas other parameters had a negative correlation with age: astigmatism (r = −0.09; P < 0.001), best-correct visual acuity (BCVA) (r = −0.04; P < 0.001), flat K (r = −0.09; P < 0.001), steep K (r = −0.06; P < 0.001), average K (r = −0.07; P < 0.001), and J0 (r = −0.05; P < 0.001). For hyperopic patients, astigmatism (r = 0.35; P < 0.001), BCVA (r = 0.11; P < 0.001), flat K (r = 0.30; P < 0.001), average K (0.14; P < 0.001), and central corneal thickness (r = 0.10; P < 0.001) correlated positively with age, whereas sphere (r = −0.23; P < 0.001), J0 (r = −0.31; P < 0.001), and overall blurring strength (r = −0.31; P < 0.001) had negative correlations with age.
Conclusions
This large cohort study shows age- and sex-related refractive parameters among myopic and hyperopic patients seeking refractive surgery. These parameters can explain and predict trends in patients attending refractive surgery.
Life expectancy has increased significantly in the past few decades, thus increasing the interest in studying the potential impact of age on human functions. In plastic surgery, orthopedics, and cancer, the influence of age was investigated in terms of outcome of surgeries, prognosis and prediction of treatments, , and decisions for the most appropriate treatments. In ophthalmology, intraocular pressure (IOP) increases with age, especially in the decades from the 60s to the 80s, which if not managed, leads to serious effects on vision. , Regarding refraction, changes in spherical equivalence vary with age as described by Goldblum and associates and by Lee and associates.
Characterizing age-related changes in subjects undergoing refractive surgery may be of interest as it may influence guidelines, surgical considerations, and decision making. The aim of this study was to analyze age- and sex-related changes in corneal refractive parameters for myopic and hyperopic patients.
Materials and Methods
This was a retrospective cross-sectional study. Data for the study were collected and analyzed in accordance with the policies and procedures of the Institutional Review Board of the Barzilai Medical Center and the tenets set forth in the Declaration of Helsinki.
Study Participants
This study included patients who underwent refractive surgery between January 2000 and December 2014 at Care-Vision Laser Centers, Tel-Aviv, Israel. Inclusion criteria for refractive surgery were age <18 years old, stable refraction for at least 12 months, not wearing rigid contact lenses for at least 2 weeks and not wearing soft contact lenses for 4 days, no history of autoimmune disease or diabetes mellitus, and no previous ocular surgery.
Data Collection
The medical files of patients were reviewed, and the following demographic and preoperative information were extracted: age, sex, dominant eye, uncorrected visual acuity, best corrected visual acuity (BCVA), preoperative sphere, preoperative cylinder, average K, flat K, steep K, K axis (against-the-rule, with-the-rule, or oblique) and central corneal thickness (CCT). Topographic parameters were measured with the Sirius Scheimpflug Analyzer (CSO, Costruzione Strumenti Oftalmici, Florence, Italy) and CCT measured by an ultrasonic pachymeter (Sonomed Escalon, New York).
Clinical notation of refractive error was calculated using the formulation of Thibos and associates for spherical equivalence (SE), cylindrical components (J 0 , J 45 ), and overall blurring strength (B), as previously described by Thibos and Horner, using the following equations:
SE=Sphere+Cylinder2
J0=−Cylinder2cos2α
J45=−Cylinder2sin2α
B=M2+J02+J452
Statistical Analysis
Data were analyzed using Minitab version 17 software (Minitab Inc., State College, Pennsylvania). For the analysis of continuous data, Student t -test was used for normally distributed variables and Kruskal-Wallis test for nonparametric variables. One-way analysis of variance (ANOVA) was used for comparison of multiple group averages. The Spearman test was performed to analyze the correlation between parameters. A 2-sided P value of <0.05 was considered statistically significant. Mean values are presented with their standard deviations.
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