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Results for “Visual Acuity”

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At least 199 records · Page 11Linked to original sources

PubMed1983

[Stereoscopic vision in reduced visual acuity].

Like other authors, we observed a number of cases with relatively good stereoscopic acuity despite poor visual acuity among patients with primary microstrabism. In order to analyze this observation experimentally the patients' visual acuity was reduced monocularly and binocularly, by means of semitransparent membranes of increasing density, to 0.3 and 0.1, and stereoscopic visual acuity was then examined using the Titmus and TNO tests. Both tests showed that in most cases stereoscopic vision was only moderately reduced, and in some cases not at all.

Adult↗

PubMedDate not supplied

[The standardization of near visual acuity].

The determination of close visual acuity is done accurately if the vision exam at a distance of 40 cm is standardized and if an exact estimation of the near visual acuity for professional activities of normal people and people with bad visual acuity can be made. The model of an optotype for near vision, Snellen metric type, using the Jaeger notation from 1 to 16 and also the standardized point system from 3 to 36, is presented. A professional selection of people with bad visual acuity after near visual exam is also presented.

Asthenopia↗

PubMed1985

Decreased visual acuity from optic disc drusen.

Although visual field defects occur commonly from optic disc drusen, reduction in visual acuity is rare. We describe four patients with reduced visual acuity and one with visual field constriction to the point of legal blindness that resulted from optic disc drusen. The acute episodic and stepwise nature of visual loss in some of the cases in our series suggests a vascular mechanism. Reduced visual acuity from drusen remains a diagnosis of exclusion. It should be considered, however, when visual loss has been acute and nonprogressive or stepwise in a nerve fiber bundle distribution and when visual acuity is not reduced until visual field constriction is severe.

Acute Disease↗

PubMed1986

Visual acuity with noise and music at 107 dbA.

In Exper. I, 10 normal-hearing college students performed visual acuity, visual search, and pursuit tracking tasks during music presented at 70 or 107 dbA. Only visual acuity was significantly worse during the higher sound level, which suggest that the effect existed at the relatively low level of sensory processing rather than at the level(s) of cognition and decision-making. In Exper. II, 28 similar Ss performed the visual acuity task during either music or noise presented at 70 or 107 dbA. Acuity was impaired by loud music but not by loud noise. It was suggested that the momentary peak levels in music may play a role in disrupting vestibulo-ocular control, and that some workplace noises may partake of this acoustic characteristic.

Adolescent↗

PubMed1985

Early loss of central visual acuity in glaucoma.

Central visual acuity is usually maintained until late in the course of glaucoma. Ten patients (5 men, 5 women) between the ages of 25 and 79 were found to have decreased visual acuity associated with central or centrocaecal scotomas early in their course. Five patients had chronic open-angle glucoma, three and pigmentary glaucoma, one and juvenile glaucoma, and one had Axenfeld's syndrome. A Marcus Gunn pupil was present in all six patients not on miotics. Most lost central acuity at pressures under 30 mmHg. Seven patients had vision of 20/200 or less. All with marked visual loss had a cup disc rate of .8 or greater. Other causes were carefully ruled out. Proposed mechanisms for the development of these central defects include either double Bjerrum scotomas which extend centrally or early papillomacular bundle involvement due to temporal cupping. This study demonstrates that decreased vision with associated central field loss can be a relatively early finding in glaucoma.

Adult↗

PubMed1988

An objective VER assessment of visual acuity compared with subjective measures.

Visual acuity was estimated by making amplitude measurements of the transient visually evoked response (VER) wave to pattern reversal using check sizes of 5.5, 7.5, 8.5, and 9.5 min arc. As in previous studies the 5.5 min arc check produced a response which reflected the visual acuity of the high acuity subjects, but often failed to produce a VER wave at the low acuity end. The proposal is made that where the 5.5 min arc check produces an acceptable wave (amplitude greater than 1.5 microV) then the regression line for the 5.5 check can be used to predict visual acuity. Where the VER amplitude is below 1.5 microV for this small check size then a second recording must be made using the 9.5 min arc check and the visual acuity predicted from the 9.5 check regression line.

Adolescent↗

PubMed1993

[Evaluation of visual acuity of small children with preferential looking methods].

With preferential looking (PL) techniques, especially the Acuity Card Procedure (Teller Acuity Cards), the visual acuity in small children can be determined. PL-testing was used in 294 children in the Strabismus and Amblyopia Department of the Ophthamology Hospital in Kraków. These children had been directed from other ophthalmologic departments. Almost all of them showed general retardation and their visual acuity could not be tested with traditional methods. The testing was considered positive when the visual acuity of each eye could be determined separately. Such result was obtained in 230 children (78.2% of all patients). The remaining group consisted of 59 children (20.0%) who were tested only binocularly and 5 children (1.8%) by whom no testing was possible.

Child↗

PubMed1993

Distance visual acuity and monovision.

We have investigated aspects of visual acuity with monovision correction. Binocular distance visual acuity with monovision was approximately equal to monocular visual acuity for addition powers (monocular defocus) of +1.00 to +2.50 D, using both high and low contrast logMAR visual acuity charts. Neither the eye chosen to be defocused (dominant or nondominant) or pupil size (3.5, 5 and 7 mm) affected the binocular visual acuity loss with monovision for high contrast charts. We also investigated the effect of induced residual astigmatism (+0.50, +1.00, and -1.00 D) on binocular distance visual acuity in monovision correction. Residual astigmatism caused a significantly greater reduction of binocular visual acuity in the monovision condition than it did in normal binocular conditions. This effect appears to be related to a process of meridional interocular suppression. It may therefore be of clinical importance to correct low amounts of residual astigmatism in monovision corrections to provide optimum binocular visual acuity.

Adult↗

PubMed1989

Relations between visual acuity, refraction and the pattern reversal visual-evoked cortical potential in aphakia.

The investigations included 20 aphakic patients. Relations were established between visual acuity, refraction and the pattern reversal visual-evoked cortical potentials (PRVECP). Close correlations were found between the three values. The optimum correction for obtaining best visual acuity, the skiascopic value, and the correction value for obtaining the largest PRVECP amplitude at minimum peak time differ by an average of 0.5 dptr.

Aged↗

PubMed1990

The component of gaze selection/control in the development of visual acuity in children.

Visual acuity was tested for 180 eyes of 90 children in four age groups using three types of test charts. Subjects read the same 10 high-contrast letters in Snellen (line) format, as isolated-letter flash cards, and as repeat-letter flash cards. Group mean line and group mean isolated-letter acuity showed similar progressive improvements with age. A subgroup of 24 of 50 eyes of 4- to 5-year-olds (15 of 25 subjects) and 3 of 50 eyes of 6- to 7-year-old (2 of 25 subjects) had low Snellen acuity. Of this low-acuity subgroup of 27 eyes, 10 scored above average for their age group on the repeat-letter chart. We concluded that abnormal lateral interactions were not the explanation for the immaturity of Snellen acuity in these 10 eyes. We suggest that an important factor in the low acuities of these 10 eyes is delayed development of the selection and/or control of gaze direction. Some eyes with excellent Snellen acuity showed high crowding. For example, there were five such eyes in the oldest group. We suggest that the excellent acuities of at least two of these eyes are limited by minor inaccuracies in gaze selection and/or control rather than by lateral interaction.

Aging↗

PubMed1989

[Behavioral determination of visual acuity in 1-to-4-year-old children].

Visual acuity was assessed in 210 children aged 1 to 4 years using the Acuity card method. Visual acuity is expressed in minutes of arc, indicating the minimal angle for separate perception of two lines. Binocular visual acuity showed a gradual growth from 1.8 to 0.9 min, arc and monocular visual acuity from 1.7 to 1 min. arc during this age period. Adult values of 0.65 min. arc(binocular) and 0.70 (monocular) were not yet reached at 4 years of age. Age norms for visual acuity in children from 1 to 4 years of age were determined. The success rate for binocular visual acuity assessment was 99.5% at all ages and increased for monocular acuity assessment from 50% in the 1 to 2 year old to 100% in the 4 year olds. Acuity assessment was fast (test time 3.3 and 2.0 minutes for assessment of binocular and monocular acuity respectively). The inter-observer reliability of the binocular assessment in the same child was high.

Child Behavior↗

PubMed1986

Visual acuity of the preschool child: a review.

The need for visual acuity assessment in preschool children has long been recognized, yet there are no standardized visual acuity norms or screening criteria. This report reviews the literature on distance visual acuity in the preschool child. The areas of review include: methods of assessment of visual acuity; visual acuity norms obtained with these tests; reasons for the variations in reported visual acuity norms; variations in referral criteria for vision screenings; testability reported for various visual acuity tests; and important design principles and recommendations for preschool visual acuity tests. It is concluded that a well designed preschool visual acuity test should consist of high contrast Snellen optotypes without directional components that progress in 0.1 log steps down to a level of 6/3. To improve testability, a matching or forced choice response should be used. Of the tests that have been standardized, STY-CAR (Sheridan-Gardiner) comes closest to meeting these criteria.

Child↗

PubMed2000

Monocular versus binocular visual acuity as measures of vision impairment and predictors of visual disability.

PURPOSE: To examine the relationship between monocular and binocular visual acuities as predictors of visual disability in a population-based sample of individuals 65 years of age and older. METHODS: Two thousand five hundred twenty community-dwelling residents of Salisbury, Maryland, between the ages of 65 and 84 years of age were recruited for the study. Corrected visual acuity was measured monocularly and binocularly using ETDRS charts. Reading speed, face discrimination, and self-reported difficulty with visual tasks were also determined. RESULTS: Binocular acuity is predicted with reasonable accuracy by acuity in the better eye alone, but not by the widely used American Medical Association (AMA) weighted-average algorithm. The AMA algorithm significantly underestimates binocular acuity when the interocular acuity difference exceeds one line. Monocular acuity and binocular acuity were significantly better predictors of reading speed than the AMA weighted score or a recently proposed Functional Vision Score (FVS). Monocular acuity in the better eye, binocular acuity, and the AMA and FVS algorithms were equally good predictors of self-reported vision disability. None of the acuity measures were good predictors of face recognition ability. CONCLUSIONS: The binocular acuities of older individuals can be inferred from measures of monocular acuity. There is little evidence for binocular inhibition when the monocular acuities in the two eyes are unequal, as opposed to the widely used AMA algorithm for computing binocular visual impairment. For tasks that are strongly associated with visual acuity, such as reading, this association can be captured from measures of monocular acuity and does not require separate assessment of binocular acuity.

Aged↗

PubMed1990

The visual acuity of the lynx.

Visual evoked potentials were recorded from the occipital scalp of two anaesthetized Lynx (Lynx europea) in response to alternating gratings of various spatial frequencies and contrasts. The visual acuity of the Lynx was found to be around 5-6 c/deg, i.e. very close to the visual acuity of the cat and by far inferior to human acuity.

Animals↗

PubMed1985

Some statistical concepts in the analysis of vision and visual acuity.

As conventionally recorded, visual acuity data constitute an ordinal scale of measurement. An investigation of four different clinical samples shows that visual acuity is not normally distributed amongst these populations. Furthermore, acuity is often measured on charts which, by the inherent restriction of the stimulus size, have the effect of truncating the upper limit of the scale producing, in statistical terms, an incomplete distribution. The distribution of acuity for each sample is found to be adequately described in terms of the equation: F(x) = Ax alpha (T - x) beta, where F(x) is the cumulative distribution of the statistical population, T is the truncation level (known), x is the Snellen decimal acuity (known) and A, alpha and beta are parameters. Alternative analytical procedures based upon this model, which overcome these limitations, are discussed.

Humans↗

PubMed1990

A comparative study of grating and recognition visual acuity testing in children with anisometropic amblyopia without strabismus.

Bailey-Lovie-Ferris visual acuity charts and Teller visual acuity cards were used to compare recognition and grating visual acuity at near testing distances in 32 children with anisometropic amblyopia without strabismus. Appropriate optical corrections were worn. Test-retest intraobserver reliability was higher for letters (r =.95) than for gratings (r = .68). Using 20/30 visual acuity or better as the criterion for normal visual acuity, eight eyes with letter visual acuities ranging from 20/42 to 20/138 would have been inaccurately found to be normal by using the Teller visual acuity cards alone. Grating visual acuity measurements tended to be better than letter visual acuity; and, in general, they did not worsen proportionately with poorer letter visual acuity.

Adolescent↗

PubMed1987

Contact lens fitting relation and visual acuity in keratoconus.

The presence of visual decrement in keratoconus is widely recognized, but little is known about the effect of different contact lens fitting philosophies on visual acuity. We studied 10 eyes with keratoconus, each of which was tested with an automated visual acuity device while wearing rigid contact lenses of varying base curves and diameters. Lenses used were large, flat lenses and small, steep lenses, fitted from 0.4 mm flatter to 0.4 mm steeper than the average keratometric measurement in 0.1-mm increments, including parallel to the average corneal curvature. A small improvement in visual acuity was noted with the flat lenses, equalling approximately one-half line of visual acuity, which, although statistically significant, was not deemed to be clinically significant. In addition, a decrement in visual acuity of keratoconus patients with centrally placed cones was noted and is discussed.

Contact Lenses↗

PubMed1999

Potential acuity pinhole: a simple method to measure potential visual acuity in patients with cataracts, comparison to potential acuity meter.

OBJECTIVE: To describe the potential acuity pinhole (PAP) test and compare its accuracy to the potential acuity meter (PAM) in predicting visual outcome after cataract surgery. STUDY DESIGN: Prospective case series. PARTICIPANTS: A total of 56 preoperative patients with cataracts participated. MAIN OUTCOME MEASURES: Accuracy of predicting postoperative distance visual acuity was measured. METHODS: Lines of inaccuracy were calculated by subtracting actual postoperative best-corrected distance visual acuity (BCVA) from predicted values. Variables analyzed were method of prediction, preoperative BCVA, and preoperative spherical equivalent. RESULTS: The PAP test predicted visual outcomes within 2 lines in 100%, 100%, and 56% of eyes with preoperative BCVA of 20/50 and better (group 1), 20/60 to 20/100 (group II), and 20/200 and worse (group III), respectively. The PAM predictions within 2 lines for the same groups were 42%, 47%, and 0%, respectively. Mean lines of inaccuracy of PAP predictions were 0.83, 1.11, and 3.50 lines for groups I, II, and III, respectively. Mean lines of inaccuracy for PAM predictions were 2.50, 2.68, and 6.22 lines for the same groups. Differences in lines of prediction between PAM and PAP were 1.67 (P = 0.004), 1.58 (P = 0.0002), and 2.72 lines (P = 0.0001) for groups I, II, and III, respectively. There was no statistically significant correlation between PAP predictions and preoperative myopic spherical equivalent. CONCLUSIONS: The PAP test is a simple, inexpensive, and relatively reliable method to estimate visual outcome after uncomplicated cataract surgery in eyes with no coexisting disease. It is less accurate in patients with preoperative BCVA worse than 20/200. It appears to be more predictive than PAM.

Adult↗