Search results for "Visual Acuity"
showing 10 items of 456 documents
Long-term comparison of corneal aberration changes after laser in situ keratomileusis: mechanical microkeratome versus femtosecond laser flap creatio…
2010
Purpose To compute and compare visual acuity, refractive outcomes, and anterior corneal aberration changes after myopic laser in situ keratomileusis (LASIK) with flap creation by a mechanical microkeratome and by a femtosecond laser. Setting Private practice refractive surgery center, Valencia, Spain. Design Comparative case series. Methods Patients were assigned to have LASIK flap creation with a mechanical microkeratome (Carriazo-Barraquer) or a femtosecond laser (IntraLase). The Visx S2 excimer laser was used for myopic ablation in all cases. Main outcome measures included uncorrected and corrected distance visual acuities and the defocus equivalent. Higher-order aberrations (HOAs) were …
Influence of different types of astigmatism on visual acuity
2016
[EN] Purpose To investigate the change in visual acuity (VA) produced by different types of astigmatism (on the basis of the refractive power and position of the principal meridians) on normal accommodating eyes. Methods The lens induced method was employed to simulate a set of 28 astigmatic blur conditions on different healthy emmetropic eyes. Additionally, 24 values of spherical defocus were also simulated on the same eyes for comparison. VA was measured in each case and the results, expressed in logMAR units, were represented against of the modulus of the dioptric power vector (blur strength). Results LogMAR VA varies in a linear fashion with increasing astigmatic blur, being the slope o…
Visual performance of two simultaneous vision multifocal contact lenses
2012
Purpose To evaluate and compare the visual performance of two simultaneous vision multifocal contact lenses (CLs). Methods In this cross-over study design 20 presbyopic subjects were fitted with two different simultaneous vision multifocal CLs (the PureVision Multifocal Low Add and Acuvue Oasys for Presbyopia) in random order. After 1 month, binocular distance visual acuity (BDVA) under photopic (85 cd/m2) and mesopic (3 cd/m2) conditions, binocular near visual acuity (BNVA), binocular distance contrast sensitivity function (CSF) under photopic and mesopic conditions, binocular near CSF and defocus curve were measured. Subjects were then refitted with the alternative correction and the proc…
Quality of vision with the Acri. Twin asymmetric diffractive bifocal intraocular lens system.
2007
To assess the quality of vision in patients who had implantation of asymmetric Acri. Twin bifocal diffractive intraocular lenses (IOLs) by evaluating distance and near visual acuities and photopic and mesopic contrast sensitivity under monocular and binocular conditions.Fernández-Vega Ophthalmological Institute, Oviedo, Spain.The study comprised 343 consecutive patients who had bilateral implantation of the Acri. Twin system: a distance-weighted 737D IOL and a near-weighted 733D IOL. Monocular and binocular best corrected distance visual acuities, best distance corrected near visual acuity, and distance contrast sensitivity under photopic (85 cd/m(2)) and mesopic (5 cd/m(2)) conditions were…
Visual function after implantation of a diffractive aspheric trifocal intraocular lens
2016
Purpose To evaluate distance, intermediate, and near vision after bilateral implantation of a diffractive aspheric trifocal intraocular lens (IOL). Methods This study enrolled 204 eyes of 102 patients who had bilateral implantation of the AT LISA tri 839MP IOL. Monocular and binocular uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA) (4 meters), monocular and binocular uncorrected near visual acuity (UNVA) and distance-corrected near visual acuity (DCNVA) (30, 40 centimeters), binocular uncorrected intermediate visual acuity (UIVA) and distance-corrected intermediate visual acuity (DCIVA) (50, 60, 70 centimeters), the defocus curve, and binocular photopic…
Diurnal variations in visual performance for disposable contact lenses.
2013
The purpose of this study is to compare the visual performance provided by different daily disposable contact lenses and to analyze its variation over time.Visual performance was evaluated in terms of visual acuity (VA) and contrast sensitivity (CS) in 15 myopic subjects (-0.50 to -4.00 diopters) who had been previously fitted with each one of the following seven types of soft contact lenses: DAILIES TOTAL1 (Alcon, Forth Worth, TX), DAILIES AquaComfort Plus (Alcon), 1-DAY ACUVUE TruEye (JohnsonJohnson Vision Care, Jacksonville, FL), 1-DAY ACUVUE MOIST (JohnsonJohnson Vision Care), SofLens daily disposable (BauschLomb, Rochester, NY), Proclear 1 Day (CooperVision, Fairport, NY), and Clariti …
Methodological Aspects of the Application of the Naka-Rushton Equation to Clinical Electroretinogram
1993
The nonlinear relation between stimulus intensity and response amplitude of the electroretinogram (ERG) scotopic b wave can be described by a curve based on the Naka-Rushton (NR) equation. Up to now, the NR equation has been used to assess the features of the normal and pathological ERG, but the best approach for a correct evaluation of the parameters is still debatable. The parameters are thought to be related to the different conditions of retinal activities. The method is well known in experimental laboratories but is quite unusual at the clinical level. In the present paper the derivative analysis of the NR function is proposed as an easier approach to understand the variations of the N…
Human eyes do not need monochromatic aberrations for dynamic accommodation
2017
Purpose To determine if human accommodation uses the eye's own monochromatic aberrations to track dynamic accommodative stimuli. Methods Wavefront aberrations were measured while subjects monocularly viewed a monochromatic Maltese cross moving sinusoidally around 2D of accommodative demand with 1D amplitude at 0.2 Hz. The amplitude and phase (delay) of the accommodation response were compared to the actual vergence of the stimulus to obtain gain and temporal phase, calculated from wavefront aberrations recorded over time during experimental trials. The tested conditions were as follows: Correction of all the subject's aberrations except defocus (C); Correction of all the subject's aberratio…
Visual Performance of Four Simultaneous-Image Multifocal Contact Lenses Under Dim and Glare Conditions
2014
To assess and compare the effects of four simultaneous-image multifocal contact lenses (SIMCLs), and those with distant-vision-only contact lenses on visual performance in early presbyopes, under dim conditions, including the effects of induced glare.In this double-masked crossover study design, 28 presbyopic subjects aged 40 to 46 years were included. All participants were fitted with the four different SIMCLs (Air Optix Aqua Multifocal [AOAM; Alcon], PureVision Multifocal [PM; BauschLomb], Acuvue Oasys for Presbyopia [AOP; JohnsonJohnson Vision], and Biofinity Multifocal [BM; CooperVision]) and with monofocal contact lenses (Air Optix Aqua, Alcon). After 1 month of daily contact lens wear…
Accommodation Responds to Optical Vergence and Not Defocus Blur Alone.
2017
Purpose To determine whether changes in wavefront spherical curvature (optical vergence) are a directional cue for accommodation. Methods Nine subjects participated in this experiment. The accommodation response to a monochromatic target was measured continuously with a custom-made adaptive optics system while astigmatism and higher-order aberrations were corrected in real time. There were two experimental open-loop conditions: vergence-driven condition, where the deformable mirror provided sinusoidal changes in defocus at the retina between -1 and +1 diopters (D) at 0.2 Hz; and blur-driven condition, in which the level of defocus at the retina was always 0 D, but a sinusoidal defocus blur …