Evaluating internal and ocular residual astigmatism in Chinese myopic children (original) (raw)
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Longitudinal change and stability of refractive, keratometric, and internal astigmatism in childhood
Investigative ophthalmology & visual science, 2015
To assess longitudinal change in refractive, keratometric, and internal astigmatism in a sample of students from a population with a high prevalence of with-the-rule (WTR) astigmatism and to determine the optical origins of changes in refractive astigmatism. A retrospective analysis of longitudinal measurements of right eye refractive and keratometric astigmatism in Tohono O'odham Native American children was conducted. Changes in refractive and keratometric astigmatism per year were compared in a younger cohort (n = 1594, 3 to <11 years old) and an older cohort (n = 648, 11 to <19 years old). Data were analyzed in clinical notation (Cyl) and vector notation (J0, J45). On average, refractive astigmatism (means: 1.19 diopters [D] Cyl, +0.54 J0, +0.03 J45) resulted primarily from WTR corneal astigmatism (means: +0.85 J0, -0.02 J45) and against-the-rule (ATR) internal astigmatism (means: -0.31 J0, +0.05 J45). Mean longitudinal changes in astigmatism were statistically signifi...
Distribution of the anterior, posterior, and total corneal astigmatism in healthy eyes
International ophthalmology, 2017
To evaluate the magnitude and axis orientation of the anterior, posterior, and total corneal astigmatism in normal healthy eyes of an Iranian population. In a prospective cross-sectional study, ophthalmic and anterior segment parameters of 153 healthy eyes of 153 subjects were evaluated by Galilei dual Scheimpflug analyzer. The magnitude and axis orientation [with-the-rule (WTR), against-the-rule (ATR), and oblique] of the anterior, posterior, and total corneal astigmatism measurements (ACA, PCA, and TCA) were compared according to the age, sex, and other ophthalmic parameters. The mean ± SD age of the study population was 30 ± 5.9 years. The mean magnitude was 1.09 ± 0.76 diopters (D) for ACA, 0.30 ± 0.13 D for PCA, and 1.08 ± 0.77 D for TCA. Males had a significantly higher magnitude of PCA than females (p = 0.041). Most eyes had a WTR anterior astigmatism and an ATR posterior astigmatism. The WTR astigmatism had a higher mean magnitude compared to the ATR and oblique astigmatism ...
Contribution of posterior corneal astigmatism to total corneal astigmatism
Journal of Cataract and Refractive Surgery
PURPOSE: To determine the contribution of posterior corneal astigmatism to total corneal astigmatism and the error in estimating total corneal astigmatism from anterior corneal measurements only using a dual-Scheimpflug analyzer. SETTING: Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA. DESIGN: Case series. METHODS: Total corneal astigmatism was calculated using ray tracing, corneal astigmatism from simulated keratometry, anterior corneal astigmatism, and posterior corneal astigmatism, and the changes with age were analyzed. Vector analysis was used to assess the error produced by estimating total corneal astigmatism from anterior corneal measurements only. RESULTS: The study analyzed 715 corneas of 435 consecutive patients. The mean magnitude of posterior corneal astigmatism was -0.30 diopter (D). The steep corneal meridian was aligned vertically (60 to 120 degrees) in 51.9% of eyes for the anterior surface and in 86.6% for the posterior surface. With increasi...
Journal of Cataract and Refractive Surgery, 2014
Prospective case series. METHODS: Corneal astigmatism was measured using a Scheimpflug camera combined with a corneal topographer (Sirius). Keratometric astigmatism, anterior corneal astigmatism, posterior corneal astigmatism, and total corneal astigmatism were evaluated. Vector analysis was performed according to the Naeser method. RESULTS: One hundred fifty-seven eyes were enrolled. Keratometric astigmatism was with the rule (WTR), against the rule (ATR), and oblique in 84.0%, 11.5%, and 4.5% of eyes, respectively. Posterior corneal astigmatism exceeded 0.50 D and 1.00 D in 55.4% of eyes and 5.7% of eyes, respectively. The mean posterior corneal astigmatism was 0.54 D, inclined 91 degrees in relation to the steeper anterior corneal meridian. The steepest meridian was vertically aligned in 93.0% of cases. Compared with total corneal astigmatism, keratometric astigmatism overestimated WTR astigmatism by a mean of 0.22 D G 0.32 (SD), underestimated ATR astigmatism by 0.21
誗AIM: To assess the anterior corneal astigmatism (ACA) and posterior corneal astigmatism (PCA) patterns across various age groups. We also evaluated the association between magnitudes and axes of the ACA and PCA across these age groups. 誗 METHODS: The present study was a cross-sectional analysis of clinical data of 381 eyes. We converted the clinical astigmatic notation to vector notation for analysis of ACA and PCA. We estimated the correlation between magnitude and axes of the ACA and PCA in the whole population and in four age groups (5-19, 20-39, 40-59, and 逸 60y). We used random effects linear regression models for estimating the association between the magnitudes of ACA and PCA. 誗 RESULTS: The mean of the magnitude of the ACA (3郾 59D) and the PCA (0郾 50D) was highest in children (5 to 9y). Overall, the magnitude of the ACA ranged from 0D to 10郾 0 Diopters (D) and the magnitude of the PCA ranged from 0 to 3郾 5 D. There was a significant correlation between the ACA and the PCA in the younger age group (r = 0郾 85, P < 0郾 001). In those 60y or older, the PCA increased by 0郾 04 units (95% confidence intervals: 0郾 005, 0郾 07; P = 0郾 03) with each unit increase in the ACA, the increase was the smallest in this age group. 誗CONCLUSION: It will be prudent to measure the both the magnitude and axis of the PCA, particularly in those above 60y rather than rely on rule-of-thumb calculations based on ACA parameters for IOL power calculation.
Longitudinal Changes in Corneal Asphericity in Myopia
Optometry and Vision Science, 2000
To report the change in shape of the peripheral cornea (asphericity, Q) as it relates to myopia progression in adolescence. Methods: Forty-eight subjects with initial ages between 11 and 13 years of age were observed for 5 years. Each subject had participated in a variety of soft contact lens studies and all had worn daily wear soft contact lenses successfully for the 2 years before collection of the second data set. Results: Myopia increased by an average of 1.46 D and was strongly correlated with a 0.56-mm increase in axial length. There was no contribution to the change in myopia from the change in central radius of the cornea. A significant (p < 0.01, one tail) correlation was found between Q and the progression of myopia. Principal axis analysis yielded a slope of ؊0.04 in Q per diopter of increase in myopia. Conclusion: These data show a shift to a more positive Q (in the oblate direction) with increased myopia.
Prevalence of Astigmatism in 4- to 6-Year-Old Population of Mashhad, Iran
Background: Astigmatism is a correctable cause of visual impairment in childhood. It increases the incidence of amblyopia in children. Objectives: In this report, we intended to describe the prevalence of the amount and axis of astigmatism, astigmatism components, and associations of astigmatism with age, gender and spherical equivalent in under six years old children through a population-based study. Patients and Methods: This report was a part of the cross-sectional Mashhad Eye Study in which 3675 of 4-6 years old children in Mashhad kindergartens were selected through random cluster sampling, of which, 3701 participated in the study (response rate: 98.3%). Refractive astigmatism was determined using a retinoscope (HEINE BETA-200, Germany) and defined as a cylinder power of more than 0.5 diopter (D). Corneal astigmatism was measured using Pentacam (Oculus Optikgerate GmbH, Germany). Results: The prevalence of refractive astigmatism of more than 0.5D in at least one eye was 51.4% (...
Association between Refractive Error Types and Asthenopia in Primary School Students
Majalah Kedokteran Bandung, 2021
Refractive error is a condition in which the cornea and lens fail to focus the light, resulting in reduced visual efficiency. Twelve million children are experiencing refractive errors worldwide and uncorrected refractive errors in children have been reported to cause asthenopia. This study aimed to determine the association between the types of refractive errors and asthenopia in children. This cross-sectional study was conducted on 111 students aged 10-13 years old in a public elementary school in Indonesia, SDN Penjaringan 10, in 2019. A questionnaire was used to assess asthenopia and the Snellen Chart, trial frames, and trial lenses were used for refractive errors examination. It was demonstrated that 87.4% of respondents experienced asthenopia, and 53.2% of respondents suffered from uncorrected refractive errors, mostly due to myopia. Fisher's exact test results showed an association between refractive errors and asthenopia (p=0.019) with all myopic students experienced asthenopia. However, there was no significant association between astigmatism and asthenopia (p=0.754). In conclusion, not all types of refractive errors are associated with asthenopia.
Non-Orthogonal Corneal Astigmatism among Normal and Keratoconic Brazilian and Chinese populations
Current eye research, 2018
To investigate the prevalence of non-orthogonal astigmatism among normal and keratoconic Brazilian and Chinese populations. Topography data were obtained using the Pentacam High Resolution (HR) system ® from 458 Brazilian (aged 35.6 ± 15.8 years) and 505 Chinese (aged 31.6 ± 10.8 years) eyes with no history of keratoconus or refractive surgery, and 314 Brazilian (aged 24.2 ± 5.7 years) and 74 Chinese (aged 22.0 ± 5.5 years) keratoconic eyes. Orthogonal values of optical flat and steep powers were determined by finding the angular positions of two perpendicular meridians that gave the maximum difference in power. Additionally, the angular positions of the meridians with the minimum and maximum optical powers were located while being unrestricted by the usual orthogonality assumption. Eyes were determined to have non-orthogonal astigmatism if the angle between the two meridians with maximum and minimum optical power deviated by more than 5° from 90°. Evidence of non-orthogonal astigma...