The human eye may present refractive errors as myopia, hypermetropia and astigmatism. This article presents the development of an Ensemble of Classifiers as part of a Refractive Errors Measurement System. The system analyses Hartmann-Shack images from human eyes in order to identify refractive errors, wich are associated to myopia, hypermetropia and astigmatism. The ensemble is composed by thre...

PURPOSE To develop a minimum set of analyses and a format for presentation of outcomes of astigmatism correction by laser systems that reshape the cornea. METHODS An Astigmatism Project group was created under the auspices of the American National Standards Institute (ANSI) Z80.11 Working Group on Laser Systems for Corneal Reshaping. The Astigmatism Project Group was made up of experts in ast...

Purpose: To determine the prevalence of refractive condition and its risk factors among students in Mashhad. Methods: A total of 2510 students representing a cross-sectional of the population of Mashhad were sampled using random cluster sampling strategy. Primary and middle school students underwent cycloplegic refraction. The refractive errors of high school students were measured using non-cy...

PURPOSE To assess the clinical outcomes of femtosecond laser-assisted keratoplasty (FLAK) using the VisuMax femtosecond laser system, and to compare them with those of conventional penetrating keratoplasty (PK). METHODS We retrospectively examined 20 eyes of 20 consecutive patients undergoing FLAK and 20 eyes of 20 age- and diagnosis-matched patients undergoing conventional PK. We quantitativ...

1.1 Definition Astigmatism (from the Greek “a” meaning absence and “stigma” meaning point) is a refractive error (ametropia) that occurs when parallel rays of light entering the nonaccommoding eye are not focused on the retina [American Academy of Ophthalmology (AAO), 2007]. Astigmatism occurs when incident light rays do not converge at a single focal point. The cornea of the normal eye has a u...

PURPOSE To assess astigmatic reduction and rotational stability of Rayner T-flex toric intraocular lenses (IOL) (573T and 623T; Rayner Intraocular Lenses Ltd) in a series of cataract surgery patients with corneal astigmatism >1.50 diopters (D). METHODS This prospective, observational study included 27 eyes from 22 consecutive patients with pre-operative regular corneal astigmatism ≥1.50 D in ...

PURPOSE The relationship between astigmatic refractive errors and their associated visual acuity has been studied in recent years in the context of refractive power space. The influence of the axis of astigmatism remains a matter of controversy. Our goal in this study is to provide additional experimental evidence to clarify this subject. The influence of the simulated axis orientation was comp...

We know that the expression emmetropia is a conventional one and that in fact all normal human eyes have mild degrees of spherocylindrical errors (Shilo, 1997) or consist of a bitoric optical system, i.e. have principal meridians of relatively higher and lower powers at right angles. It is generally accepted that genetic factors have a significant role in determining ocular refractive status as...

Purpose To compare two calculators for toric intraocular lens (IOL) calculation and to evaluate the prediction of refractive outcome. Methods Sixty-four eyes of forty-five patients underwent cataract surgery followed by implantation of a toric intraocular lens (Zeiss Torbi 709 M) calculated by a standard industry calculator using front keratometry values. Prediction error, median absolute err...