Search results for "Subjective refraction"
showing 10 items of 12 documents
What is the influence of parents' myopia on their children's myopic progression? A 22-year follow-up study.
2016
Purpose To study the connection between parental myopia and their children's myopia from school age to adulthood. Methods Two hundred and forty myopic schoolchildren (119 boys, 121 girls, mean age 10.9 years) with no previous spectacles for myopia were recruited to a 3-year treatment trial with different use of spectacles. Follow-ups were performed at mean ages of 13.9, 23.7 and 33.2 years for 238, 176 and 170 subjects respectively. Subjective refraction was calibrated to the spherical equivalent at corneal level (SEcor). Corneal refractive power (CR) and axial length (AL) were measured. Parental myopia was assessed with a questionnaire and the children assigned accordingly to one of three …
Prevention of hyperopic surprise after LASIK in patients with refractive multifocal intraocular lenses.
2011
Purpose. Three cases of patients who developed a similar hyperopic defect in refraction following laser in situ keratomileusis (LASIK) after multifocal intraocular lens (IOL) implantation are described. Methods. Ophthalmologic evaluation including refractive status, corrected and uncorrected visual acuity (both at far and near), and corneal topography in patients presenting similar hyperopic refractive surprise in one eye as a result of LASIK refinement of residual ametropia after refractive multifocal IOL implantation. Results. Laser in situ keratomileusis enhancement for residual ametropia of −1.00 to −1.50 D in patients with a prior implantation of refractive multifocal IOL resulted in a…
Subjective Refraction Techniques in the Frame of the Three-Dimensional Dioptric Space
2001
A novel heuristic approach to the well-known representation of the dioptric power in a three-dimensional space is presented. It is shown how this theoretical framework is ideal for discussing the principles of several subjective refraction methods. In particular, this formalism is used to justify the stenopaic slit refraction, the Barnes subjective refraction technique, and the Jackson cross-cylinder procedure. In view of this analysis, some modifications to the traditional procedures are proposed.
Digitālās refrakcijas pielietojums labākā koriģētā redzes asuma novērtēšanai
2021
Darbs ir uzrakstīts angļu valodā uz 36 lappusēm, satur 20 attēlus, 4 tabulas un 35 literatūras avotus. Darba mērķis ir pārbaudīt redzes asumu ar trim refrakcijas metodēm: autorefraktometriju, subjektīvo refraktometriju un digitālo refraktometriju ar ierīci ESSILOR Vision R-800. Tika salīdzināta refrakcija 15 subjektiem vecumā no 12 līdz 40 gadiem. Refrakcijas dati tika pārveidoti optiskā stipruma vektora formā. Rezultāti: Statistiski nozīmīgas atšķirības tika konstatētas redzes asumam, bet ne optiskā stipruma vektoriem, kas bija ļoti līdzīgi viens otram. Secinājums: digitālā refrakcija ar precizitāti 0,01 D pie nepārtrauktas optiskā stipruma maiņas parādīja labāku redzes asumu pat pie zema …
An alternative clinical routine for subjective refraction based on power vectors with trial frames.
2016
PURPOSE Subjective refraction determines the final point of refractive error assessment in most clinical environments and its foundations have remained unchanged for decades. The purpose of this paper is to compare the results obtained when monocular subjective refraction is assessed in trial frames by a new clinical procedure based on a pure power vector interpretation with conventional clinical refraction procedures. METHODS An alternative clinical routine is described that uses power vector interpretation with implementation in trial frames. Refractive error is determined in terms of: (i) the spherical equivalent (M component), and (ii) a pair of Jackson Crossed Cylinder lenses oriented …
Anisometropia of ocular refractive and biometric measures among 66- to 79-year-old female twins
2016
Purpose To examine the prevalence of anisometropia of spherical refraction (AnisoSR), astigmatism (AnisoAST) and spherical equivalent (AnisoSE) and their associations with spherical refraction (SR), refractive astigmatism (AST), spherical equivalent (SE) and interocular differences of ocular biometric parameters among elderly female twins. Methods Refraction of 117 monozygotic (MZ) and 116 dizygotic (DZ) female twin subjects aged 66–79 years was assessed with an auto-refractor (Topcon AT) and controlled by subjective refraction. Corneal refraction, anterior chamber depth and axial length were measured with a Zeiss IOL Master. Participants with eyes operated for cataract or glaucoma were exc…
Visual Acuity in Simple Myopic Astigmatism: Influence of Cylinder Axis
2006
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 compared with other factors that affect visual acuity such as the particular design of the test and the differences between eyes. Methods. Simple myopic astigmatism from 0 to 3.00 D, in steps of 0.25 D, and with five different axes between 0° and 90°, were simulated on four healthy eyes of young observer…
Optical factors influencing the amplitude of accommodation
2017
AbstractThe purpose of this work was to find plausible predictors among optical parameters that may explain the inter-individual differences in subjective amplitude of accommodation not explained by age. An exploratory multivariable regression analysis was carried out retrospectively on a dataset with 180 eyes from 97 subjects (ages ranged from 20 to 58years). Subjective amplitudes of accommodation were recorded with the use of a custom-made Badal system. A commercial aberrometer was used to obtain each eye’s wavefront during the full range of accommodation. The plausible predictors under study were pupil diameter in the unaccommodated eye, its reduction with accommodation; fourth- and six-…
Clinical Impact of a Spontaneous Decentration of a Phakic Refractive Lens
2011
PURPOSE To evaluate the clinical impact and possible causes of a spontaneous decentration of a phakic refractive lens (PRL) implanted in a highly myopic eye, and analyzing the visual, refractive, and aberrometric outcome as well as the possible causes for this phenomenon. METHODS The description of a case of bilateral high myopia corrected by implantation with the phakic intraocular lens (pIOL) PRL (Carl Zeiss Meditec, Germany) is presented and documented. Both eyes had similar anatomical configuration, and therefore, a pIOL (Model 101) with the same size was implanted without any associated intraoperative complication. Clinical outcomes were evaluated during a 3-month follow-up. RESULTS Im…
The stenopaeic slit: an analytical expression to quantify its optical effects in front of an astigmatic eye.
2001
The stenopaeic slit is a trial case accessory used in subjective refraction, especially when high astigmatism is present. In spite of its simplicity, the effect of the slit when it is not oriented along one of the principal meridians of the examined eye is difficult to predict, even in terms of classical geometrical optics. In this paper, the optical principles of the slit are considered with full details in the theoretical framework of the dioptric power space. An analytical expression to obtain the residual refractive error when a stenopaeic slit is placed in front of an astigmatic eye at any orientation is deduced. In the light of these results, some aspects of the clinical procedure are…