Some intriguing concepts of visual optics cannot be explained by ray tracing. However, they can be clarified using wavefront formalism. Its main advantage is in the use of the concept of vergence, which is very helpful in interpreting the optical phenomena involved in the neutralization of the ametropias. In this line of thinking, the major role of a lens is in the creation of a new light sourc...

OBJECTIVE To evaluate the effects of excimer laser in situ keratomileusis in correcting severe myopia and astigmatism after penetrating keratoplasty. METHODS Excimer laser in situ keratomileusis was performed on ten eyes of ten patients to correct high ametropia in cases having previously undergone penetrating keratoplasty. RESULTS After surgery, all grafts remained clear and no corneal gra...

PURPOSE There is currently great interest in comparing data for the prevalence of myopia in different parts of the world, particularly in view of the suggestion that, in recent decades, marked increases have occurred in prevalence among children and young adults in some areas. This work investigates the factors that affect the comparison and interpretation of sets of myopia prevalence data for ...

Methods: Baseline and 6-week data from a longitudinal controlled study were analyzed. Subjects were 70 preschoolers (mean age, 4.6 years; 60.0% were female; and 85.7% were Latino), including 35 children with previously uncorrected ametropia and 35 emmetropic control subjects. Ametropia was defined as bilateral hyperopia of 4.00 diopters (D) or more in children aged 3 to 5 years, astigmatism of ...

A prospective series of 25 eyes received an intraocular lens (IOL) of power calculated for planned ametropia, by means of the formulae of R. D. Binkhorst, from data of axial length, corneal curvature, and postoperative anterior chamber depth. All the postoperative refractions were within the +/- 2 D range from the predicted refraction, confirming the clinical value of such calculation. A retros...

PURPOSE To measure the changes in astigmatism and in the degree of anisometropia when ametropes respond to accommodative stimulation. METHODS The accommodative responses of ametropes were binocularly measured with an improved photorefractometer (PR-1100), which objectively measured binocular refraction in all meridians simultaneously, when a visual fixation target was shown in natural space a...

PURPOSE To explore the associations between anisometropia and spherical ametropia, astigmatism, age, and sex. METHOD Associations between the prevalence and magnitude of anisometropia with age, sex, spherical power, and cylindrical power, were assessed in a group of 90,884 subjects attending optometry practices in the United Kingdom. Logistic regression models were used to assess the independ...