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Results for “Visual Acuity”

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At least 649 records · Page 36Linked to original sources

PubMed1984

Assessment and prediction of visual acuity in 3- to 4-year-old children born prior to term.

Previous studies of school-age children born prior to term indicate that they often have visual acuity that is slightly poorer than normal. However, visual acuity results for preschool-age preterm children have not been reported. In this study, we used the operant preferential looking procedure to measure the visual acuities of 23 3- to 4-year-old preterm children. The results indicated that, although many of the children had acuities within the normal range, the average acuity of the preterm children was slightly poorer than that of full-term children of the same age, even when children with significant refractive errors were eliminated from the sample. Neither birthweight, gestational age at birth, nor the presence of respiratory distress syndrome during infancy were predictive of later visual acuity. However, preferential looking acuity screening at 4 months corrected age did have some predictive value, in that 3 of the 4 infants who failed to complete testing at 4 months showed poor performance at 3 to 4 years of age.

Birth Weight↗

PubMed1997

[Visual acuity and use of eyeglasses after implantation of a diffractive multifocal lens].

BACKGROUND: The implantation of a diffractive multifocal lens (dMIOL) as alternative to a monofocal lens is justified if after surgery there is practically no need to wear glasses. PATIENTS AND METHODS: 31 patients had an implantation of a total of 35 dMIOLs (3M 815 LE). We evaluated the visual acuity, the refractive data and the patients' attitude to wearing glasses. The average age was 67.0 +/- 11.8 years. Follow up took place after 18.7 +/- 5.4 months. RESULTS: The mean value of the uncorrected distance acuity was 0.59 +/- 0.17 and the corrected distance acuity 0.96 +/- 0.13. The uncorrected near acuity amounted to Jg 2.40 +/- 0.94, best distance correction was Jg 1.49 +/- 0.55. The patients still accepted an average of 0.68 +/- 0.37 dpt for the best near correction (near vision over the diffractive near focus) and thus achieved Jg 1.46 +/- 0.55. At the best distance correction plus 3.5 dpt, the near visual acuity was improved to 1.03 +/- 0.17. 54.8% of the patients indicated that they did not use glasses at all. 32.3% stated that they only used glasses for reading. 9.7% wore bifocals all the time, and 3.2% always used glasses for the distance. CONCLUSIONS: Regarding distance vision, the dMIOL is equivalent to monofocal lenses. Without any correction the results of the dMIOLs for the near vision are superior to monofocal lenses. Glasses can be dispensed with if the uncorrected visual acuity of the operated eye is at least 0.6 Jg 2-3 after surgery and the other eye too, does not need any correction. In case the postoperative visual acuity is worse, good visual acuity of the other eye may render glasses unnecessary. Part of the patients put up with a correctable loss of visual acuity in order not to become dependent on glasses. The need to wear glasses may be decreased considerably by implanting a dMIOL in both eyes and by avoiding postoperative refraction errors.

Adult↗

PubMed2006

[Visual acuity and binocular vision in children with pseudophakia].

PURPOSE: To evaluate the results of cataract surgery in children with IOL implantation. MATERIALS AND METHODS: Our research involved 106 children (156 eyes) with congenital and traumatic cataract, in age from 18 months to 18 years, who underwent cataract surgery with intraocular lens implantation. We evaluated visual acuity for far vision and binocular vision after surgery. RESULTS: Visual acuity over 0.5 in unilateral congenital cataract was found in 27.25%, in traumatic cataract in 73%, whereas in bilateral congenital cataract visual acuity over 0.5 we received in 75% of operated children. Full binocular vision was obtained in children with good visual acuity (0.5 and more), with appropriate alignment of the eyes: 13.1% in unilateral congenital cataract, 45.4% in traumatic cataract and 55% in congenital bilateral cataract. CONCLUSIONS: Cataract surgery with intraocular lens implantation results in increase of visual acuity and in achievement binocular vision, if surgery is carried out in the early period, after it had been diagnosed.

Adolescent↗

PubMed2002

Sensitivity and specificity of visual acuity screening for refractive errors in school children.

PURPOSE: To examine the optimal cutoff point for the use of the visual acuity test to screen for refractive errors in schoolchildren. METHODS: In a sample of schoolchildren between 7 and 9 years old, visual acuity testing was performed using modified ETDRS charts monocularly without optical aids by trained personnel. Cycloplegic autorefraction was performed in each eye. The screening efficacy of using various cutoff points for referring children for further optometric/ ophthalmic assessment was studied. Myopia was defined as a spherical equivalent of at least -0.5 D, hyperopia a spherical equivalent of at least +2.0 D, and astigmatism a cylinder of at least -1.0 D in at least one eye. The sensitivity, specificity, and predictive values were calculated using each patient as a case; a receiver operator curve was plotted. RESULTS: A total of 1,028 children were tested. A satisfactory sensitivity/specificity profile was obtained using a referral criterion of visual acuity worse than or equal to 0.28 logarithm of the minimum angle of resolution in at least one eye. In this scenario, the sensitivity and specificity of this screening test were 72% (95% confidence interval [CI], 68 to 76) and 97% (95%CI, 95 to 98), respectively. The positive and negative predictive values were 96% (95%CI, 93 to 98) and 78% (95%CI, 75 to 82), respectively. CONCLUSIONS: The modified ETDRS visual acuity chart can be used to predict refractive errors in schoolchildren in Singapore in a sensitive and specific manner using a referral criterion of worse than or equal to 0.28 logarithm of the minimum angle of resolution.

Child↗

PubMed2006

Computerized dynamic visual acuity with volitional head movement in patients with vestibular dysfunction.

OBJECTIVES: Patients with uncompensated vestibular dysfunction frequently report blurred vision during head movement, a symptom termed oscillopsia. One way to measure the functional deficit associated with an impaired vestibulo-ocular reflex is by comparing visual acuity from a baseline condition in which there is no head movement to visual acuity obtained during a dynamic condition with head movement. A previously described test incorporated a treadmill upon which patients walked during assessment of visual acuity. The objective of the current investigation was to evaluate an alternative method of assessing dynamic visual acuity that uses volitional head movement instead of walking on a treadmill. METHODS: Fifteen participants with normal vestibular function and 16 participants with impaired vestibular function were enrolled. All participants performed the visual acuity task under baseline conditions with no movement and also under dynamic conditions that included 1) walking on a treadmill and 2) volitionally moving their head in the vertical plane. RESULTS: No difference in performance was observed between the treadmill task and the volitional head movement task. Participants with impaired vestibular function performed more poorly under the dynamic conditions than did participants with normal vestibular function. CONCLUSIONS: The results suggest that the volitional head movement paradigm may be useful in identification of patients with functional deficits of the vestibulo-ocular reflex.

Adult↗

PubMed1999

Visual acuity outcomes of patients 50 years of age and older with high myopia and untreated choroidal neovascularization.

OBJECTIVE: To evaluate visual outcomes of untreated submacular choroidal neovascularization (CNV) in patients 50 years of age and older with high myopia. DESIGN: Retrospective observational case series. PARTICIPANTS: Twenty-two eyes in 22 patients were studied. All were 50 years of age and older with myopia of 6.0 diopters (D) or greater or an axial length of 25.5 mm or greater. Patients had untreated CNV documented by clinical examination and fluorescein angiography at two medical centers between 1986 and 1997. INTERVENTION: Demographic and clinical data were abstracted from patients' medical records. MAIN OUTCOME MEASURE: Visual acuity at 1 year after CNV diagnosis. RESULTS: The study included 22 eyes of 22 patients (mean age, 63.1 years; mean refraction, -11.0 D). Baseline visual acuity (VA) in the study eye was 20/40 or greater in 2 (9%) patients, 20/50 to 20/150 in 9 (41%) patients, and 20/200 or less in 11 (50%) patients. Drusen were present in seven (32%) eyes, and lacquer cracks were noted in ten (45%) eyes. Mean refractive error was -7.0 D for patients with drusen and -12.5 D for patients without drusen. Choroidal neovascularization was less than 0.25 disc diameters (DD) in 11 (50%) eyes, 0.25 to 0.5 DD in 5 (23%) eyes, and greater than 0.5 DD in 6 (27%) eyes. Visual acuity in the study eye 1 year after CNV diagnosis was 20/40 or greater in 3 (14%) patients, 20/50 to 20/150 in 3 (14%) patients, and 20/200 or less in 16 (73%) eyes. The presence of drusen was significantly associated with older age and a lower degree of myopia but was not associated with size of the CNV or visual acuity outcome. CONCLUSION: When compared to patients younger than 50 years of age with high myopia and CNV reported in previous publications, the patients in the current series generally have poorer visual outcomes.

Aged↗

PubMed1995

Test-retest variability and correlations between tests of texture processing, motion processing, visual acuity, and contrast sensitivity.

PURPOSE: To compare the test-retest variability (reliability) and the relations among clinical tests of texture and motion processing, visual acuity for high- and low-contrast letters, and the Pelli-Robson contrast sensitivity test. METHODS: In 20 normally sighted subjects, monocular visual acuity for letters of 96% and 11% contrast, Pelli-Robson contrast sensitivity, and motion-defined and texture-defined letter recognition thresholds were measured on each of two different days. RESULTS: Test-retest correlation coefficients were 0.75, 0.91, 0.61, 0.90, and 0.84 and bivariate test-retest regression slopes were 1.0, 1.1, 0.8, 1.0, and 1.2 for high- and low-contrast acuity, contrast sensitivity, and motion and texture processing, respectively. The inter-test correlations with both test and retest significant were as follows: visual acuity for high-contrast letters vs. visual acuity for low-contrast letters; and recognition threshold for texture-defined letters vs. acuity for letters of both high and low contrast. CONCLUSION: Test-retest variability for the tests of motion and texture processing were at least as low as for established clinical tests of high and low contrast acuity and contrast sensitivity. We conclude that these new tests offer a reliable means of obtaining clinical information which complements that provided by conventional tests with luminance-defined letters.

Adolescent↗

PubMed2000

Lack of correlation between visual acuity and fixation stability after photocoagulation for diabetic maculopathy.

PURPOSE: To study the correlation between changes in visual acuity and changes in fixation stability after retinal photocoagulation for diabetic maculopathy. MATERIAL: Twenty-four patients with diabetic maculopathy and visual acuity (VA) ranging between 0.05-0.77 were studied at baseline and 1, 3, 6 and 12 months after retinal photocoagulation. Fixational eye movements were quantified from video recordings of the ocular fundus obtained with the Rodenstock scanning laser ophthalmoscope. RESULTS: No correlation was found between the changes in the quantitative measures of the fixational eye movements (amplitude and retinal area of fixation) and the changes in VA 12 months after retinal photocoagulation. Three patients all with VA<0.31 at baseline had the fixation centre located more than 3 deg from the centre of the foveal avascular zone (FAZ) at one or more of the follow-up examinations, and one of these patients used three different locations of fixations during the follow-up period. CONCLUSION: Changes in fixation stability after retinal photocoagulation are complex but not related to changes in visual acuity.

Adult↗

PubMed2000

[Corneal infection in wearers of contact lenses: causes, effect on visual acuity and prevention].

This is a 5-year retrospective survey of corneal infection in wearers of optical contact lenses (OCL). 23 of the 61 patients (38%; Hasharon Hospital) with positive cultures wore OCL. Visual acuity improved in 15 (65%), no change was noted in 4 (17.5%) and there was deterioration in 4 (17.5%), as compare with status on admission. Pseudomonas aeruginosa was the most common cause of infections among OCL wearers. The improvement in visual acuity expected due to wearing OCL was affected by infections. Those after Staphylococcus albus infections had the highest rate (100%) of improvement in visual acuity and after Ps. aeruginosa the lowest rate (57.2%) of improvement, as well as the highest rate of deterioration (42.8%) found following recovery. OCL wearers are at higher risk for damage to visual acuity following corneal infection, and highly virulent infections in OCL wearers are responsible for a high risk of damage to visual acuity.

Contact Lenses↗

PubMed2005

[Visual acuity and full-field electroretinography in patients with Usher's syndrome].

PURPOSE: Usher's syndrome (US) is a group of genetically distinct autosomal conditions, characterized by sensorineural hearing loss accompanied by a retinal dystrophy indistinguishable from retinitis pigmentosa (RP). The purpose of this study was to analyze full-field electroretinography (ERG) and visual acuity (VA) among patients with type I and II Usher's syndrome. METHODS: Electroretinography responses and visual acuity were studied in 22 patients (mean age at test = 26.8+/-16.8 years). Seventeen patients had SU type I and 5 patients were diagnosed as Usher's syndrome type II. RESULTS: Mean visual acuity was 0.9 logMAR (20/160, Snellen equivalent) for patients with Usher's syndrome type I and 0.4 logMAR (20/50, Snellen equivalent) for patients with Usher's syndrome type II. Scotopic rod and maximal responses were non-detectable in both groups. Mean amplitude for oscillatory potentials was 14.5 microV+/-6.1 in Usher's syndrome type I and 12.6 microV+/-5.2 in Usher's syndrome type II. Cone responses were non-detectable in 95% of the patients with Usher's syndrome I and in 100% of patients with Usher's syndrome II. Mean amplitude for 30 Hz flicker photopic cone response was 3.1 microV+/-4.1 for Usher's syndrome type I and 1.0 microV+/-0.6 for type II with mean implicit time of 34.0 ms+/-6.2 (US I) and 35.8 ms+/-3.1 (type II). CONCLUSIONS: Visual acuity was relatively preserved in both groups, however Usher's syndrome II group showed better visual acuity results. Electroretinography findings were severely reduced in both groups, with most patients showing non-detectable rod and cone responses.

Adolescent↗

PubMed2006

Functional visual acuity in Stevens-Johnson syndrome.

PURPOSE: To evaluate the correlation of functional visual acuity (FVA) measurement with ocular surface findings in patients with Stevens-Johnson syndrome (SJS). DESIGN: Prospective comparative study. METHODS: Sixty-nine eyes of 38 patients with chronic SJS assessed at the Tokyo Dental College, Tokyo Medical Center, and the Kyoto Prefectural University of Medicine, Department of Ophthalmology, Kyoto, Japan, were studied. Twenty eyes of 10 normal subjects and 40 eyes of 20 patients with Sjögren syndrome (SS) were also studied. Conventional Landolt visual acuity (VA) and FVA examinations and slit-lamp examinations were performed. FVA was measured continuously by the FVA measurement system during a 30-second blink-free period in one eye. The visual maintenance ratio (VMR) was calculated as follows: VMR = [(2.7 - FVA)/(2.7 - baseline VA)], where logarithm of minimal angle of resolution values of FVA were entered into the formula and 2.7 represented the lowest visual acuity in this series. Slit-lamp examinations, Schirmer test, and fluorescein vital stainings were also performed in all subjects. RESULTS: VMR was markedly lower in patients with SJS compared with patients with SS and controls. FVA values showed a relation with the presence of corneal opacity and vascularization. CONCLUSIONS: The FVA measurement system is not only a useful tool in the evaluation of dynamic VA changes, but also reflects the ocular surface clinical findings in SJS.

Adult↗

PubMed2004

Visual acuity in the water maze: sensitivity to muscarinic receptor blockade in rats and mice.

A visual acuity task performed in the water maze in rats [Behav. Brain Res. 119 (2001) 77] was used to reveal the sensitivity of the visual system to muscarinic receptor blockade. Intraperitoneal injection of 0.2 mg/kg scopolamine had no effect, but 2 mg/kg severely compromised visual acuity, but did not affect the swim strategy to solve the task. Spatial learning in a reference memory version of the water maze, however, was impaired by 0.2 mg/kg scopolamine. It was also confirmed that the same visual acuity task is applicable to C57BL6/J mice. The visual deficit induced by 2 mg/kg scopolamine was less severe compared to rats, possibly due to a change in swim strategy in the drug condition. The effect of scopolamine on spatial reference memory in mice was not tested in this study. These data suggest that it may be possible to dissociate drug-induced effects on memory from changes in sensory perception.

Analysis of Variance↗

PubMed2005

Visual acuity, environmental complexity, and social organization in African cichlid fishes.

The authors studied the effects of habitat complexity and social organization on visual acuity in closely related cichlid fishes (the Ectodini clade). The authors quantified habitat complexity among sand, intermediate, and rock habitats using chromatic difference measures (intensity analysis). Visual acuity was measured behaviorally, using optomotor/optokinetic responses to rotating square-wave stimuli. The rock-dwelling Asprotilapia leptura exhibited the best visual ability, compared with the intermediate and sand-dwelling species, Xenotilapia spilotera and Xenotilapia flavipinnis. The authors then compared effects of social organization. The lek-forming, polygamous Enantiopus melanogenys showed better visual acuity than that of the pair-bonding, monogamous X. flavipinnis. The authors' results are the first to demonstrate that species-specific differences in visual acuity are associated with differences in both the physical and social environment.

Animals↗

PubMed1992

[Visual acuity and driver's licence among young people. Are routine vision tests necessary?].

The minimum visual acuity for obtaining a driver's licence for smaller vehicles in Norway is 0.5 (5/10). However, visual acuity is not routinely tested on application for the licence. Among 720 conscripts examined by a draft board, five (0.694%) had a visual acuity of less than 0.5, and did not have spectacles or lenses. The estimated standard deviation is 0.31%. The upper 95% one sided confidence limit was estimated to be 1.46% (Poisson-distribution). It is concluded that checking the vision of all applicants for a driver's licence would have only a marginal effect on safety.

Adult↗

PubMed2001

Near-field visual acuity in Japanese jungle crows (Corvus macrorhynchos).

The near-field visual acuity of three Japanese jungle crows (Corvus macrorhynchos) was determined by means of operant conditioning. The task was discrimination of grating stimuli, and the threshold was measured by up-and-down method between sessions. To keep observing distance constant, a photo sensor was used and the head position was behaviorally fixed. The average visual acuity was 8.4 cycles/degree. When compared with other birds, this result is better than that of pigeons, and worse than that of predators.

Animals↗

PubMed1991

Relation between spherical refractive error and visual acuity.

The relation between a spherical refractive error and visual acuity is investigated and the results compared with previous studies. This study, unlike most of the previous studies, presents a mathematical model that includes a pupil size factor. It also examines a theoretical relation between refractive error and visual acuity which predicts that there should be a linear relation among refractive error (E), the pupil diameter (D), and minimum angle of resolution (A), over a wide range of refractive errors.

Humans↗

PubMed1989

Chart for visual acuity screening.

The statistical basis underlying the use of several visual acuity charts is examined. A new chart which offers theoretical and practical advantages for visual acuity screening is described.

Humans↗

PubMed1990

[Amblyopia: reading speed in comparison with visual acuity for gratings, single Landolt Cs and series Landolt Cs].

In the treatment of amblyopia in preschool children, a means of predicting later reading ability would be helpful. This prediction might be possible using a test for visual acuity where the results correlate with reading ability in adult patients with amblyopia. We measured the following four parameters in 18 experienced readers with strabismic amblyopia: (1) time spent reading ten lines of a standard text in one of three magnifications, (2) visual acuity for gratings, (3) visual acuity for single Landolt Cs, and (4) visual acuity for crowded Landolt Cs (one Landolt C flanked by two full rings on each side each at a distance of 2.6 min of arc). The reading text was presented on paper at a distance of 40 cm; the subject had a choice of three magnifications. The acuity tests were generated by a computer on a VDU at 4.6 m. The relative impairment of the amblyopic eye was defined as the quotient between the performance of the amblyopic and the good eye. In addition, the difference between the times spent reading the ten lines with the amblyopic and with the good eye was calculated.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗