نتایج جستجو برای: secondary astigmatism
تعداد نتایج: 305593 فیلتر نتایج به سال:
We studied the role of native astigmatism and ocular aberrations on best-focus setting and its shift upon induction of astigmatism in 42 subjects (emmetropes, myopes, hyperopes, with-the-rule [WTR] and against-the-rule [ATR] myopic astigmats). Stimuli were presented in a custom-developed adaptive optics simulator, allowing correction for native aberrations and astigmatism induction (+1 D; 6-mm ...
OBJECTIVE To analyze the effectiveness and safety of corneal relaxing incisions (CRI) in correcting keratometric astigmatism during cataract surgery. METHODS A prospective study of two groups: control group and treatment group. A treatment group included 25 eyes of 25 patients who had combined clear corneal phacoemulsification, IOL implantation and CRI. A control group included 25 eyes of 25 ...
BACKGROUND The expectations of post-removal cataract surgery patients are extremely high, and best vision acuity is expected. The best refractive results are influenced by two factors - cataract surgical removal and the corneal astigmatism correction. Currently, the two most often applied corneal astigmatism removal methods are laser surgery and toric intraocular lens implantation, with the lat...
PURPOSE To evaluate the relationship patterns between astigmatism axes of fellow eyes (rule similarity and symmetry) and to determine the prevalence of each pattern in the studied population. METHODS This population-based study was conducted in 2015 in Iran. All participants had tests for visual acuity, objective refraction, subjective refraction (if cooperative), and assessment of eye health...
We previously showed that different types of aberration defocus, coma, and secondary astigmatism affect reading performance via different mechanisms. In this paper, we show the contrary result that, for identification of isolated letters, the effects of rendering different types of aberration can be described by a single cross-correlation-based metric. Aberrations reduce the effective resolutio...
PURPOSE This study investigated the relationship between uncorrected astigmatism and early academic readiness in at-risk preschool-aged children. METHODS A vision screening and academic records review were performed on 122 three- to five-year-old children enrolled in the Philadelphia Head Start program. Vision screening results were related to two measures of early academic readiness, the tea...
PURPOSE To derive a method of quantifying corneal topographic astigmatism (CorT) that accurately represents manifest refractive cylinder. SETTING Private practice, Melbourne, Australia. DESIGN Retrospective study. METHOD Axial power measurements obtained using topography in right eyes and left eyes were analyzed. For each Placido ring, an astigmatism value was calculated. The ring astigma...
Purpose To identify genes and genetic markers associated with corneal astigmatism. Methods A meta-analysis of genome-wide association studies (GWASs) of corneal astigmatism undertaken for 14 European ancestry (n=22,250) and 8 Asian ancestry (n=9,120) cohorts was performed by the Consortium for Refractive Error and Myopia. Cases were defined as having >0.75 diopters of corneal astigmatism. Sub...
BACKGROUND The aim of the study is to raise the awareness of the influence of coma-like higher-order aberrations (HOAs) on power and orientation of refractive astigmatism (RA) and to explore how to account for that influence in the planning of topography-guided refractive surgery in eyes with coma-like-aberrations-dominant corneal optics. METHODS Eleven eyes with coma-like-aberrations-dominan...
PURPOSE Astigmatism is a very common refractive error in humans, but its etiology is poorly understood. The primary purpose of this study was to determine whether alterations in visual experience would result in astigmatism in chicks. METHODS Longitudinal and cross-sectional data were obtained from chicks that were raised undergoing four different visual manipulations known to alter axial eye...
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