Search results for "Pupil Size"
showing 10 items of 20 documents
Influence of contrast polarity on the accommodative response☆
2018
espanolObjetivo Evaluar los cambios de la respuesta acomodativa del ojo al leer un texto en diferentes condiciones de polaridad de contraste: letras negras sobre fondo blanco (condicion BoW) y letras blancas sobre fondo negro (condicion WoB). Metodos En este estudio experimental participaron dieciocho sujetos de edades comprendidas entre 21 y 41 anos. Se obtuvo objetivamente la respuesta acomodativa (AR) del ojo al leer un texto con polaridad de contraste BoW o WoB con un sistema de optica adaptativa que corregia todas las aberraciones salvo las propias del sujeto. Se estudiaron dos tamanos de letra diferentes (condiciones de agudeza visual), mostrados en una micropantalla. Se midio la AR d…
Curvature of iris profile in spectral domain optical coherence tomography and dependency to refraction, age and pupil size - the MIPH Eye&Health …
2016
Purpose Optical coherence tomography (OCT) of the anterior segment allows quantitative analysis of the geometry of the iris. We performed spectral domain OCT examinations in healthy emmetropic, hyperopic and myopic subjects to investigate iris curvature and its associations. Methods In a cross-sectional study, out of 4617 eyes (2309 subjects) those with refractive errors of +3 dioptres were identified by objective refraction. The iris was examined using the anterior segment mode of a spectral domain 3D OCT-2000 (Topcon Inc., Japan) in the temporal meridian, and OCT scans were investigated with respect to presence and amount of convex and concave iris configuration. Ninety-three eyes of 50 s…
Light distortion of soft multifocal contact lenses with different pupil size and shape
2020
Purpose: To study the light distortion effects of soft multifocal contact lenses and the influence of different pupil size and shape.Methods: A total of 14 eyes of 7 healthy contact lens users (mean age 28.6 +/- 8.5 years) were recruited. The "Light Disturbance Analyser" device was employed for light characterization. The selected lenses were the monthly disposable "Biofinity multifocal" (CooperVision, CA, USA), both centre-distance and centre-near designs (addition power + 2.50 D). Two circular pupils of 3 mm and 5 mm of diameter, and an elliptical shape (3 horizontal and 5 vertical mm) were used. Metrics such as the light distortion index (LDI), best-fit circle radius and its irregularity…
Effect of phenylephrine on static and dynamic accommodation
2018
Purpose We tested the hypothesis that changes in accommodation after instillation of Phenylephrine Hydrochloride (PHCl) observed in some studies could be caused by changes in optics. Methods We performed two experiments to test the effects of PHCl on static and on dynamic accommodation in 8 and 6 subjects, respectively. Objective wavefront measurements were recorded of the static accommodation response to a stimulus at different distances or dynamic accommodation response to a sinusoidally moving stimulus (between 1 and 3 D of accommodative demand at 0.2 Hz). The responses were characterized using two methods: one that takes into account the mydriatic optical effects on the accommodation pr…
How Do Different Digital Displays Affect the Ocular Surface?
2020
Digital display use has been accepted as a contributing factor to dry eye disease. Nowadays, plenty of new models of digital displays have been developed, and the differences in their nature and the ways in which they are set and used may contribute to differences in the eye-related problems they cause.This study aimed to analyze the differences in ocular surface, tear film, and visual fatigue parameters after reading on different digital displays, with and without initial instillation of artificial tears.Thirty-one healthy individuals ranging in age from 20 to 26 years (mean ± standard deviation, 21.26 ± 1.73 years) were included in this prospective clinical study. Subjects' ocular surface…
Visual quality differences between orthokeratology and LASIK to compensate low-moderate myopia.
2013
PURPOSE: To assess the differences in visual performance between orthokeratology (ortho-k) and laser in situ keratomileusis (LASIK) for the treatment of low-to-moderate myopia. METHODS: An adaptive optics visual simulator (Imagine Eyes) was used to simulate the wavefront aberration patterns induced by ortho-k and LASIK for low and moderate myopia on 10 healthy eyes. Visual acuity (VA) at 100%, 50%, and 10% contrast levels and contrast sensitivity (CS) at 10, 20 and 25 cycles per degree (cpd) were then measured for 3- and 6-mm pupil sizes. RESULTS: Differences in VA for 3-mm pupil diameter were not found between ortho-k and LASIK. For 6-mm pupil size, LASIK provided significantly better VA v…
The effect of simulated normal and amblyopic higher-order aberrations on visual performance.
2012
Purpose To study the effect of simulated amblyopic and normal higher-order aberrations on visual performance of normal eyes. Methods To assess visual function, an adaptive optics visual simulator was used to compensate volunteers' ocular aberrations and simulate the wavefront aberration patterns found in healthy and amblyopic eyes in 7 healthy individuals. Visual acuity for high (100%), medium (50%), and low (10%) contrast and contrast sensitivity at 10, 20, and 25 cycles per degree (cpd) were measured after simulation of both pattern aberrations. The modulation transfer function and the point spread function were computed based on the aberration data. All measures were taken for 3 and 5.5 …
Image quality with multifocal intraocular lenses and the effect of pupil size
2007
Purpose To analyze the image quality with a refractive and 2 hybrid refractive–diffractive multifocal intraocular lenses (IOLs) in vitro to determine the IOL modulation transfer function (MTF) following the EN-ISO international standard for distance and near vision and to study the IOLs' behavior with different pupil sizes. Setting Fundacion Oftalmologica del Mediterraneo, Valencia, Spain. Methods This study evaluated 4 IOLs: the hybrid refractive–diffractive AcrySof ReSTOR SN60D3 (Alcon) and Tecnis ZM900 (AMO), the refractive ReZoom NXG (AMO), and the monofocal AcrySof SN60WF (Alcon). The MTF was calculated from the cross-line spread function recorded with the OPAL Vector System (Image Sci…
Changes in physiological astigmatism of human eye during accommodation in emmetropes (Conference Presentation)
2017
Introduction: Most young emmetrope eyes are far from ideal and have some degree of minor spherocylindrical error including also physiological astigmatism. Because of the changes in the shape of optical interfaces, pupil size, eyelid pressure, tear film, body posture, binocularity and accommodation astigmatism is considered as constantly dynamic phenomenon (Cheng et al, 2004). The purpose of this study was to evaluate and quantify changes in physiological astigmatism during accommodation. Method: Twenty young emmetropes with mean age 24 ± 4 years were selected for the study. Refraction and accommodative response were measured monocularly for dominant eye with an open-field infrared autorefract…
Objective assessment of the effect of pupil size upon the power distribution of multifocal contact lenses
2017
AIM: To analytically assess the effect of pupil size upon the refractive power distributions of different designs of multifocal contact lenses. METHODS: Two multifocal contact lenses of center-near design and one multifocal contact lens of center-distance design were used in this study. Their power profiles were measured using the NIMO TR1504 device (LAMBDA-X, Belgium). Based on their power profiles, the power distribution was assessed as a function of pupil size. For the high addition lenses, the resulting refractive power as a function of viewing distance (far, intermediate, and near) and pupil size was also analyzed. RESULTS: The power distribution of the lenses was affected by pupil siz…