PURPOSE To evaluate how small amounts of astigmatism affect visual acuity and the minimum astigmatism values that should be corrected to achieve maximum visual performance. SETTING Optics Laboratory, University of Murcia, Murcia, Spain. DESIGN Case series. METHODS A wavefront sensor was used to measure astigmatism and higher-order aberrations (HOAs) in normal young eyes with astigmatism r...

PURPOSE We estimated the contribution of the gradient refractive index (GRIN) and lens surfaces to lens astigmatism and lens astigmatic angle as a function of age in human donor lenses. METHODS Human lenses were imaged, ex vivo, with 3D-spectral optical coherence tomography (OCT) and their back focal length was measured using laser ray tracing. The contribution of lens surfaces and GRIN to le...

We investigated pseudophakic residual astigmatism in order to minimize postoperative refractive astigmatism. We examined 110 eyes of 87 patients who had undergone phacoemulsification with small incision and posterior chamber intraocular lens (IOL) implantation. Corneal astigmatism was measured using an autokeratometer (RK-5, canon), refractive astigmatism by manifest refraction, and residual as...

conclusions the prevalence of astigmatism was high in children under six years old in this study, and to control amblyopia, it is necessary to consider astigmatism at younger ages. results the prevalence of refractive astigmatism of more than 0.5d in at least one eye was 51.4% (95% confidence interval (ci): 50.7-52.1); 52.1% in girls and 50.7% in boys (p = 0.412). prevalence of astigmatism decr...

Correction of corneal astigmatism is a key element of cataract surgery, since post-surgical residual astigmatism can compromise the patient's uncorrected visual acuity. Toric intraocular lenses (IOLs) compensate for corneal astigmatism at the time of surgery, correcting ocular astigmatism. They are a predictable treatment. However, accurate measurement of corneal astigmatism is mandatory for ch...

PURPOSE Human infants exhibit a high prevalence of astigmatism. Although macaque monkeys are commonly used as animal models in experiments on early ocular growth and emmetropization, the prevalence of astigmatism in infant monkeys is unexplored. In this study we examine the prevalence and nature of astigmatism in infant monkeys. METHODS Refractive and corneal astigmatism were measured in 132,...

Purpose. To assess the amount and the axis orientation of anterior and posterior corneal astigmatism after refractive lenticule extraction (ReLEx) for myopic astigmatism. Methods. We retrospectively examined 53 eyes of 53 consecutive patients (mean age ± standard deviation, 33.2 ± 6.5 years) undergoing ReLEx to correct myopic astigmatism (manifest cylinder = 0.5 diopters (D)). Power vector anal...

Astigmatism’s defect has not yet been formulated in Physics and medical physics books theoretically. In this paper, we are trying to formulate the astigmatism’s defect. The results of formulation show that “the degree of astigmatism is negative reverse the distance that vision’s condition of astigmatism’s chart lines change conditions in dimness angle from dimness condition at infinite distance...