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PubMed1977

[Development of refraction and visual acuity of squinting children (author's transl)].

The refraction and visual acuity rates of 170 children from the age of 2 to the age of 7 suffering from squint were recorded and analysed. On the basis of our investigation we could not prove the process of emmetropisation during the growth of the eyes of squinting children in this age group. That means that the process of emmetropisation of squinting children takes place slower and later than with non-squinting children and is apparently stabilized at an age between 8 and 12 years. On the other hand--the increase of visual acuity of the normal eyes of squinting children is--as a rule-completed at the age of 5, like that of non squinting children.

Age Factors↗
PubMed1989

[Examination of central vision. Visual acuity, contrast sensitivity, color vision].

In the neurophysiological organization of the visual system, form, color, movement, and depth perception are processed separately. Therefore, sensorial examination methods should test each of these basic functions separately, since they may be affected individually or to different extents by pathologic processes. For diagnosis the limit of visual acuity, i.e., the capacity for discrimination must be searched for, using Paliaga's "limits method". Visual acuity can also be tested in infants by the preferential looking method. Contrast sensitivity is tested using sinusoidal grid patterns of varying contrast and spatial frequency. In routine practice, however, this is usually achieved more easily with acuity cards on which contrast is reduced in several stages. The "two-equation method" is a colorimetric test combining two metameric matches, red + green = yellow, and blue + green = cyan, for testing color vision. The test requires an anomaloscope or anomalometer with four light channels. With this method it is possible to test the "red", "green", and "blue" cones and the "red-green" and "blue-yellow" opponents. The test provides a qualitative and quantitative evaluation of color vision disorders. If no colorimeter is available, classic printed test can be used. However, they might never achieve the same qualitative and quantitative precision.

Color Perception Tests↗
PubMed1983

Effect of binocular variations of Snellen's visual acuity on Titmus stereoacuity.

Thirty normal subjects were tested with the Titmus stereotest varying the binocular Snellen's visual acuity from 20/20 to 20/200. From the 36 possible combinations, a nomogram describing the relationship of binocular variations of Snellen's visual acuity and stereoacuity was constructed. The nomogram provides a useful reference for comparing expected and achieved clinical results of the Titmus stereotest in normal subjects. The effects of various pathologic conditions of the eye on the relationship between Snellen's visual acuity and stereoacuity needs to be studied.

Adolescent↗
PubMed1988

Predicting visual acuity after cataract surgery using the blue field entoptoscope and projected slides.

A new method allows accurate testing of visual function behind mild-to-moderate cataracts or capsular opacities. Patients were asked to compare the number of corpuscles visualized with the blue field entoptoscope with a series of projected slides having progressively fewer drawn corpuscles. To standardize the equipment, the test was performed on 69 patients with varying degrees of macular impairment. Of the patients who selected 120 corpuscles or more, 89% had visual acuities of 20/40 or better, and those who selected 100 corpuscles or less, 82% had visual acuities of 20/50 or worse. The percentages were higher for age-related macular degeneration (ARMD) patients (100 and 85%) than for diabetic patients (33 and 75%). The same apparatus was then used to predict the potential visual acuity in 56 preoperative cataract or YAG-capsulotomy patients. Of the 23 patients with a preoperative acuity of 20/200 or better and who selected 120 corpuscles or more, 100% were 20/40 or better postoperatively.

Audiovisual Aids↗
PubMed1996

Visual acuity immediately following phacoemulsification with subconjunctival anesthesia.

The authors attempted to discover the quality of vision experienced immediately after cataract surgery by those patients receiving subconjunctival anesthesia and no postoperative patching. Eighty-five consecutive patients who underwent phacoemulsification were studied. Anesthesia was topical tetracaine followed by a subconjunctival injection of a lidocaine-bupivicaine hydrochloride-hyaluronidase mixture. Visual acuities were measured within a half hour after surgery and at 1 day postoperatively. Immediate postoperative visual acuities ranged from 20/25 to 20/200. Visual acuities were 20/40 or better in 14 patients (16.4%), 20/50 to 20/60 in 22 patients (23.5%), and 20/70 to 20/200 in 49 patients (60.1%). The early postoperative visual acuity measurements vary widely. There was a marked improvement at 1 day after surgery, with acuities becoming more aligned with expected outcomes.

Anesthesia, Local↗
PubMed2003

Visual acuity with reversed-contrast charts: II. Clinical investigation.

Snellen visual acuity was measured in 106 patients ranging in age from 20 to 88 years in routine examinations in the general refraction clinic with two kinds of charts: the standard chart using black letters on a white background and a reversed-contrast display featuring white letters on a black background. The overall ratio of the white-on-black to the black-on-white Snellen fractions was 1.043. A scattergram relating this ratio to patient age revealed that the older the patient, the more the visual acuity was improved by switching to the reversed-contrast chart, with a regression line slope of 0.5 +/- 0.10. Impairment of the eye's optics, in particular by intraocular scatter causing a widening and flattening of the eye's point-spread function, explains these findings and suggests prognostic and therapeutic value of reversing the contrast polarity of displays.

Adult↗
PubMed1994

Synthesis of the literature on visual acuity and complications following cataract extraction with intraocular lens implantation. Cataract Patient Outcome Research Team.

OBJECTIVE: To better define the effectiveness and risks of modern cataract surgery. DESIGN: Meta-analysis (formal systematic identification, selection, review, and synthesis) of published literature. PATIENTS: Patients described in 90 studies published between 1979 and 1991 that addressed visual acuity (n = 17,390 eyes) or complications (n = 68,316 eyes) following standard extracapsular cataract extraction with posterior chamber intraocular lens implantation, phaco-emulsification with posterior chamber intraocular lens implantation, or intracapsular cataract extraction with flexible anterior chamber intraocular lens implantation. MAIN OUTCOME MEASURES: The proportion of eyes with postoperative Snellen visual acuity of 20/40 or better and the proportion of eyes with each of 18 complications. RESULTS: The pooled percentage of eyes (weighted by sample size) with postoperative visual acuity of 20/40 or better was 95.5% (95% confidence interval [CI], 95.1% to 95.9%) among eyes without preexisting ocular comorbidity and 89.7% (95% CI, 89.3% to 90.2%) for all eyes. The pooled percentage of eyes experiencing complications (weighted by sample size and, when pertinent, by quality score of the individual studies but not adjusted for variation in duration of follow-up) ranged from 0.13% for endophthalmitis to 19.7% for posterior capsule opacification. Pooled proportions of eyes with other complications were as follows: bullous keratopathy, 0.3%; intraocular lens malposition/dislocation, 1.1%; clinically apparent cystoid macular edema, 1.5%; and retinal detachment, 0.7%. Pooled results for postoperative Snellen visual acuity and most complications were similar for surgery performed via phacoemulsification vs standard extracapsular cataract extraction, although comparisons of the outcomes between these procedures should be interpreted with caution. CONCLUSIONS: The published literature indicates that modern cataract surgery yields excellent visual acuity and, although not free of complications, is a very safe procedure regardless of the extraction technique used.

Aged↗
PubMed2004

Influence of wavefront aberration and corneal subepithelial haze on low-contrast visual acuity after photorefractive keratectomy.

PURPOSE: To assess low-contrast visual acuity (LCVA) after photorefractive keratectomy in relation to ocular higher-order wavefront aberration and corneal subepithelial haze. DESIGN: Prospective, cross-sectional analysis. METHODS: Photorefractive keratectomy was performed in 51 eyes of 27 subjects with myopic refractive error of -2.0 to -10.5 diopters. Ocular higher-order wavefront aberrations for a 4-mm pupil were measured using Topcon Hartmann-Shack wavefront aberrometer, and the extent of corneal subepithelial haze was quantified with Nidek TSPC-3 hazemeter before and 1 month after photorefractive keratectomy. Low-contrast visual acuity was recorded with Vector Vision CSV-1000LanC10% chart. Total higher-order, third-order (coma-like), and fourth-order (spherical-like) aberrations of the eye were determined. The influence of wavefront aberration and corneal subepithelial haze on LCVA was analyzed. RESULTS: Total higher-order, third-order, and fourth-order aberrations significantly increased by surgery (P < .001, Wilcoxon signed rank test). Photorefractive keratectomy induced a significant increase in corneal haze (P < .01), but no case presented severe corneal haze (grade 3 or greater by Fantes grading). By surgery, LCVA was reduced significantly (P < .001). The logarithm of the minimal angle of resolution LCVA showed a significant correlation with total higher-order aberration (Spearman rank correlation coefficient, r(s) = 0.642, P < .0001). Both third-order (r(s) = 0.618, P < .0001) and fourth-order aberrations (r(s) = 0.552, P < .0001) also significantly correlated with logarithm of the minimal angle of resolution LCVA. There was no correlation between the degree of corneal haze and logarithm of the minimal angle of resolution LCVA (r(s) = 0.094, P = .523). CONCLUSIONS: In eyes with mild to moderate corneal haze after photorefractive keratectomy, deterioration of LCVA is mainly attributable to increases in wavefront aberration, and not to corneal haze.

Adolescent↗
PubMedDate not supplied

"A retrospective cohort study for prognostic significance of visual acuity for near over that for distance in anisometropic amblyopia.".

A cohort of 50 anisometropic amblyopes, between the ages of 2.5 to 10 years, was studied retrospectively to assess the prognostic significance of visual acuity for near over that for distance. There is ample evidence in the literature for a significantly lower accommodative response in the anisometropic amblyopic eye. It has been proposed that the efferent accommodative dysfunction may be a fundamental and causative factor in anisometropic amblyopia. A reduced visual acuity for near over that for distance was found in 17 [34%] patients and in 11 out of these the near vision improved after an addition of +3.0D sph. When a reduced visual acuity for near, was obtained it was difficult to determine whether the visual afferent system (due to insufficient visual input), or the accommodation efferent mechanism was responsible. However an improvement in corrected near vision by addition of +3.0D sph. suggested an accommodative dysfunction. In patients with reduced visual acuity for near over that for distance, not only was the final visual outcome poor but also the onset of visual improvement in response to amblyopia therapy was delayed.

Amblyopia↗
PubMed1994

Dynamic visual acuity: a test for oscillopsia and vestibulo-ocular reflex function.

A method has been developed of clinically quantifying dynamic visual acuity (DVA), the acuity during imposed head motion in the pitch axis. In this method, visual acuity is measured using a computer-controlled projection system during vertical, sinusoidal relative motion either of the optotypes (the letters to be read) or of a servodriven swinging chair in which subjects are seated. In normal persons, the vestibulo-ocular reflex (VOR) functions adequately during imposed head movements to limit retinal image instability, making DVA independent of head velocity. During head movements the wearing of telescopic spectacles, which magnify the visual effects, can overwhelm even normal visual-vestibular interactions, producing retinal image instability leading to creation of artificial experimental oscillopsia in normal subjects. With the head stationary, optotype motion at frequencies and velocities beyond the capabilities of visual tracking also results in retinal image motion. Using these methods, DVA for both optotype and head motion was found to be degraded in a predictable fashion when the velocity of the image on the retina exceeded 2 degrees per second. In two patients with total peripheral vestibular loss, DVA was markedly impaired during head motion. As a result of the VOR deficit, this impairment of DVA was observed, even without the use of telescopic spectacles, and was predictably related to the velocity of imposed head motion. Dynamic visual acuity during imposed head motion is a quantitative and clinically feasible measure of oscillopsia that reflects functionally significant abnormalities of the VOR.

Adult↗
PubMed1990

[Idiopathic preretinal macular fibrosis. Study of correlation between morphologic changes and visual acuity].

Idiopathic preretinal macular fibrosis is an affection characterized by the development of preretinal membranes, macular distortion and, sometimes, macular edema. These changes as well as the consequent reduction of the visual acuity may vary very widely from one case to another. In this study, the degree of correlation among the various retinal morphological changes and among them and the visual acuity was investigated. This study shows that the importance of retinal distortion is strictly dependent on the appearance of the preretinal membranes that the appearance of the preretinal membrane and the importance of the retinal distortion are equally valid predictors of visual acuity, that the macular edema (defined as fluorescein leakage) depends mainly on the degree of contraction of the preretinal membrane and that such leakage does not represent the best parameter in order to predict the visual acuity.

Adolescent↗
PubMed1980

The neurology of visual acuity.

A series of patients with well defined lesions of various parts of the visual pathways was studied in an attempt to iluminate the neuropathophysiology of visual acuity. Acuity was found to remain normal in all cases with unilateral retrochiasmal lesions, including those of the optic tract. Bilateral retrochiasmal lesions involving the foveal nerve fibres on both sides impaired acuity to the same degree in both eyes. Lateral chiasmal lesions regularly produced impaired acuity in the ipsilateral eye. Midchiasmal lesions commonly led to an impairment of visual acuity in both eyes, usually asymmetrically, and roughly proportionate to the severity of the visual field defect. Compression optic neuropathy was found to reduce acuity in rough proportion to the severity of compression. It was concluded that acuity remains normal as long as either the crossing or the non-crossing neural outflow from the retinal fovea remains intact: acuity fails only when both sets of nerve fibres are compromised. A properly executed acuity test seems to be a powerful tool for detecting such conditions. The lower limit of normal acuity should never be set below 1.0 or 20/20: even this level is clearly subnormal in many subjects.

Adult↗
PubMed1993

Chronic cystoid macular edema and predictors of visual acuity.

Of 141 patients who had clinically significant cystoid macular edema (CME) following cataract surgery, 42 had a visual acuity of 20/200 or worse. Logistic regression demonstrated that of all the systemic and ocular factors studied, the best predictors of visual acuity of 20/200 or worse were the presence of iris in the wounds (odds ratio = 2.86, P = .011) and a fluorescein angiogram grade of 4 (odds ratio = 2.91, P = .0076). Entering into the logistic regression variables such as integrity of the posterior capsule, iritis, vitreous in the wound, or type of intraocular lens did not significantly improve the ability of the model to predict which patients would have poor visual acuity. This study suggests that iris incarceration in the wound may have a more important association with poor vision in patients with chronic postsurgical CME than previously thought.

Aged↗
PubMed1997

Effect of optical defocus on visual acuity in dogs.

OBJECTIVE: To determine the effect of optical defocus (such as what develops in spontaneous myopia and subsequent to cataract extraction) on visual acuity in dogs. ANIMALS: 3 young adult male Beagles. PROCEDURE: The effect of optical defocus on visual acuity was determined by sweep visual evoked potential, using a within-subjects/repeated measures design in which each dog served as its own control. Dogs were positioned so that the eye being tested was 60 cm in front of the video display, and the target was centered on the area centralis. To create ametropia relative to the video screen, a series of concave and convex spherical lenses were placed 1 cm in front of the eye, and sweep visual evoked potential acuities were obtained. RESULTS: Maximal acuity was 7.0 to 9.5 cycles/degree. Defocusing by 2.0 diopters reduces Beagle grating acuity approximately 1 octave. Mimicking aphakia resulted in a marked depression of acuity to 0.7 cycles/degree or less. CONCLUSIONS: Even mild degrees of ametropia have appreciable impact on the resolving power of the canine visual system. CLINICAL RELEVANCE: Spontaneous myopia is encountered in dogs and may be associated with impaired visual performance attributable to a reduction in visual acuity. Previous reports indicate the possibility of myopia in dogs to have a heritable component. On the basis of our results, refractive correction of aphakia is advisable, and refractive screening of dogs with demanding visual tasks (eg, service dogs, field-trial Labrador Retrievers) is recommended.

Animals↗
PubMed1975

Visual acuity improvement in eyes with corneal scars fitted with contact lenses.

The vision of 190 eyes of 130 patients with corneal scars was tested with contact lenses, of which 166 eyes subsequently were fitted with contact lenses. Over 75% of all eyes with corneal scars showed a visual acuity improvement to 6/12 or better. All eyes with a nebular or macular corneal scar and an initial visual acuity of 6/60 or better improved to 6/12 or better. The visual acuity of 77% of the eyes fitted with contact lenses, compared to the visual acuity of 36% of the same eyes obtained with spectacle lenses, improved to 6/12 or better.

Adolescent↗
PubMed1976

Visual acuity of the vampire bat, Desmodus rotundus, and its dependence upon light intensity.

The visual system of microchiropteran bats is usually considered of minor function, but reliable experimental studies are rare. In this paper the visual acuity of three (1 female, 2 male male) vampire bats (Desmodus rotundus) has been investigated in a two-choice training apparatus (striped patterns vs. gray patterns) for light intensities from 0.04 1x to 310 1x. There was a logarithmic dependence between light intensity and visual acuity. The lowest visual angle at 0.04 1x was 2 degrees 31', at 310 1x the minimum resolvable stripe width was 48'.

Animals↗
PubMed2003

Effect of intraocular lens implantation on visual acuity, contrast sensitivity, and depth of focus.

PURPOSE: To determine the role of spherical and irregular aberrations in the optics of the natural eye and after intraocular lens (IOL) implantation in terms of visual acuity, contrast sensitivity, and depth of focus. SETTING: Laboratory of Experimental Ophthalmology, University of Groningen, Groningen, The Netherlands. METHODS: Visual acuity and defocus-specific contrast sensitivity in 11 pseudophakic patients (IOL group) and 27 age-matched phakic subjects were compared. The results were obtained psychophysically. Spherical and irregular aberrations were subsequently estimated by comparing the measured myopic shift (optimum focus of contrast sensitivity at 4 cycles per degree [cpd] compared to that at 16 cpd) and depth of focus with those of theoretical eye models with varying amounts of irregular and spherical aberrations. RESULTS: The best corrected visual acuity and best corrected contrast sensitivity in the IOL group did not significantly differ from that in the phakic group. The depth of focus was larger in the IOL group at a pupil diameter of 6.0 mm (P<.05). Comparison with theoretical eye models suggested a higher amount of spherical aberration in the IOL group; irregular aberration was almost the same in both groups. CONCLUSIONS: There was a higher amount of spherical aberration in the IOL group, related to a larger depth of focus, without loss of contrast sensitivity at optimum focus or loss of visual acuity. This might contribute to better quality of vision in pseudophakic subjects than in presbyopic phakic subjects.

Contrast Sensitivity↗