PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Visual Acuity”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 667 records · Page 37Linked to original sources
PubMed2005

Visual acuity in 5-7-year-old children: individual variability and dependence on observation distance.

Accurate measurements of uncorrected binocular and monocular visual acuity were performed in 65 children aged 5-7 years at five viewing distances in the range 0.5-5.0 m by means of the test charts containing widely spaced E stimuli in four orientations. It was found that, in most children of this age, visual acuity (V) changed with test distance, as had been reported previously with older subjects. Visual acuity could be considered as practically independent of observation distance (Vmax-Vmin<or=0.2 decimal units) in <50% of children. The remaining children demonstrated evident distance dependence of visual acuity but the shape of the acuity-distance curve varied. The acuity-distance curve of most children peaked at an intermediate distance (1-2 m), the typical difference Vmax-Vmin being 0.4 decimal units. To explain the existence of an optimal observation distance in the majority of children, a number of developmental and environmental factors could be proposed that adjust the parameters of the visual system to the parameters of operational visual space and prevailing activity.

Aging↗
PubMed1993

Differences in dynamic visual acuity between athletes and nonathletes.

We surveyed the dynamic visual acuity of 53 university athletes and 46 nonathlete university students, using a Landolt C ring as a target. The target moved from left to right on screen initially at the maximum angular velocity of 300 degrees/sec. and then gradually decreased in velocity until the subject recognized the direction of the gap in the Landolt C ring. The angular velocities at which the subject correctly recognized the direction of the gap were used as the parameters of the acuity measure. When the sizes of the gap in the Landolt C ring were 42' and 28', there were no differences in the performances of the athletes and nonathletes. However, when the gap sizes were 14' and 8', athletes could recognize the gap at significantly higher velocities than the nonathletes. In this case the dynamic visual acuity of athletes was superior to that of the nonathletes.

Adult↗
PubMed2004

Effect of preoperative tear function on early functional visual acuity after laser in situ keratomileusis.

PURPOSE: To assess the effect of preoperative tear function on early changes in functional visual acuity (FVA) after laser in situ keratomileusis (LASIK). SETTING: Minamiaoyama Eye Clinic, Tokyo, Japan. METHODS: This prospective single-center study assessed the effect of preoperative and postoperative tear functions on FVA in 30 eyes of 15 patients who had LASIK. Functional visual acuity was defined as the binocular recognition acuity measured by the FVA tester (Wellsystem) during a 10-second, blink-free period. All patients had a Schirmer test with anesthesia and tear-film breakup time (BUT) measurements preoperatively and 1 day and 1 week after LASIK. Corneal topography and Landolt visual acuity and FVA measurements were performed before surgery and 1 day and 1 week after LASIK. Eyes with a Schirmer test reading less than 5.0 mm and a BUT less than 5 seconds were grouped as definite dry eye (DDE). Eyes with a normal Schirmer test score but a shortened BUT were grouped as probable dry eye (PDE). RESULTS: In all patients, the best uncorrected Landolt visual acuity was 20/20 or better at the postoperative examination times. In the DDE group, the mean preoperative FVA declined from 1.2 to 0.75 +/- 0.16 (SD) at 1 day and increased to 1.2 at 1 week. No change in FVA was observed postoperatively in the PDE group. CONCLUSION: Laser in situ keratomileusis patients with low basal tearing and full uncorrected distance Landolt acuity may experience a transient decrease in FVA that returns to baseline within 1 week.

Adult↗
PubMed1991

Visual evoked potentials and visual acuity after transurethral resection of the prostate.

Changes in visual evoked potentials, visual acuity, blood ammonia levels and serum electrolytes (Na+ and K+) after transurethral resection of the prostate using glycine as an irrigating fluid performed under subarachnoid block were studied in 12 patients, in the pre-operative and immediate postoperative periods. Visual evoked potentials (p100 latency), recorded by shift of a checkerboard pattern, increased significantly from a pre-operative value of mean (SEM) 101.18 (1.63) msec in the right eye, and 102.5 (1.47) msec in the left eye to 108.91 (1.8) msec (p less than 0.01) and 108.08 (2.53) msec (p less than 0.01) respectively in the postoperative phase. There were no changes in visual acuity as assessed by a Snellen's chart, blood ammonia levels and serum electrolyte concentrations. The amount of glycine used intra-operatively for irrigation ranged from 3 to 31 litres.

Aged↗
PubMed1985

Modification of the Kestenbaum operation for correction of nystagmic torticollis and improvement of visual acuity with the use of convergence.

In five patients with congenital nystagmus and compensatory head turn we performed a modified Kestenbaum operation intended to correct the compensatory head turn and to improve visual acuity. All patients had nystagmus without strabismus and fully developed binocular function. The nystagmus decreased but did not cease completely during the lateral gaze, and the patients adopted compensatory head turn positions to improve their visual acuity. The near acuity was better than the distance and the head turn decreased on near fixation. In such cases the original Kestenbaum procedure transfers the neutral zone to the primary position and corrects the head turn, but does not improve the visual acuity because a considerable amount of nystagmus is still present. Our aim was to perform an asymmetric Kestenbaum operation with a greater amount of surgery to the eye that turns out and a lesser amount to the eye that turns in, thus creating a postoperative divergence of the eyes. The result of compensating for this divergence (through stimulation of the fusional reserve) blocks the residual nystagmus of the neutral zone and, consequently, improves visual acuity. The results obtained from performing this modified Kestenbaum operation in five patients were very satisfactory. The compensatory head turn was corrected in all patients and remained so during the follow-up period. In four cases, the postoperative visual acuity in the neutral zone was better than before. There was no improvement in one case.

Adolescent↗
PubMed2001

[Two cases of digitalis toxicity with reversible and severe decrease of visual acuity].

BACKGROUND: We performed electrophysiologic tests on two patients with digitalis toxicity who first had photophobia and xanthopsia and revealed reversible reduced visual acuity and binocular central scotoma. CASES: The patients were a 72-year-old male and a 54-year-old male who had symptoms of digitalis toxicity. FINDINGS: The corrected visual acuity was severely decreased during digitalis toxicity, 0.02 oculus dexter (OD) and 0.1 oculus sinister (OS) in case 1 and 0.04 OD and 0.2 OS in case 2. But visual acuity recovered as the blood levels of digitalis decreased to the normal level and the corrected visual acuity was 0.7 OD and 0.8 OS in case 1 and 0.8 OD and 0.9 OS in case 2. We recorded 30 Hz-flicker electroretinogram (ERG), single flash ERG, photopic ERG, and scotopic ERG when digitalis blood levels were elevated and normal. Decreased amplitudes of 30 Hz-flicker ERG and photopic ERG suggested that photoreceptor function was disturbed at digitalis toxicity and cone dysfunction was more severely disturbed than rod dysfunction. CONCLUSION: 30 Hz-flicker ERG, as well as electrocardiogram and digitalis blood level, is a relatively convenient and useful measure of digitalis toxicity. It is necessary consiler toxicity when severe visual dysfunction is observed in patients with digitalis therapy.

Aged↗
PubMed2000

Visual acuity, lens flexure, and residual astigmatism of keratoconic eyes as a function of back optic zone radius of rigid lenses.

The purpose of this study was to determine whether the visual acuity of keratoconic eyes was affected by alteration of back optic zone radii (BOZRs) of rigid gas permeable lenses (RGP) contact lenses. Visual acuity, spherical and sphero-cylindrical over-refraction and keratometry of the front surface of the RGP lenses of nine keratoconic eyes were measured. The BOZR of the five lenses varied from steeper to flatter than that habitually worn by the subjects. The steepest lenses produced significantly greater lens flexure and residual astigmatism (P < 0.002) and worse high and low contrast visual acuity with the spherical over-refraction (P < 0.05). There was no statistical difference in visual acuity across the range of BOZR when a sphero-cylindrical over-refraction was applied. Thus reduced visual acuity in keratoconus with steep lenses is likely due to uncorrected residual astigmatism from a combination of several possible sources.

Journal Article↗
PubMed1990

[Comparison of the Lithander (Kolt test) pediatric visual acuity test with the standardized Landolt ring test].

The visual acuity values obtained with the four test figures of Lithander's "Kolt-test" have been compared with Landolt ring acuity under standardized conditions which meet the requirements of DIN 58,220 and ISO/DIS 8596/7. For a given test figure size, the Kolt-test optotypes turned out to be somewhat easier legible than the Landolt ring. On average, visual acuity measured with the Kolt-test exceeded Landolt ring acuity by 0.08 log (angle of resolution) units. Thus, according to DIN and ISO criteria, the legibility of the Kolt-test is not equivalent to the standard Landolt ring. Equal acuity values could be obtained by increasing the observation distance proposed by the manufacturer of the Kolt-test by 19%. The legibility of the four optotypes differs on adult subjects: "circle" is more difficult, "cross" is easier legible than "square" and "triangle". Confusion of Kolt-test figures is basically restricted to two pairs of two optotypes ("cross" - "triangle", "square" - "circle").

Adult↗
PubMed1996

Visual acuity in preschool children: the Chapel Hill-Durham Day-Care Vision Study.

Between 1985 and 1987, 1362 preschool children attending 45 day-care centers in Chapel Hill and Durham, North Carolina had their visual acuities tested by matching HOTV opto-types. Study participants were comprised of 718 males and 644 females. Seven hundred eight were African Americans, 607 were white, and 47 were from other ethnic groups. The children's ages were 89 < 3 years, 496 = 3 years, 531 = 4 years, and 246 > 5 years old. Only 69 children (5.1%) were unable to have their visual acuity tested in both eyes. Although there was no association between testability and either race or gender, there was a strong association with age, with 65 of the 69 children (94.2%) not testable being < 4 years old. Further, there was a clear relationship between visual acuity and age. The 1293 participants (2586 eyes) whose visual acuity was measured successfully in both eyes revealed that 2471 eyes (95.4%) had visual acuities of 20/40 or better. There were significantly more African Americans (56 or 8.4%) than whites (23 or 4.0%) in the 20/40-1 to 20/100 category.

Black or African American↗
PubMed1995

Impact of age, various forms of cataract, and visual acuity on whole-field scotopic sensitivity screening for glaucoma in rural Taiwan.

OBJECTIVE: To evaluate the impact of age, various forms of cataract, and visual acuity on whole-field scotopic sensitivity screening for glaucoma in a rural population. DESIGN: Clinic-based study with population-based recruitment. SETTING: Jin Shan Township near Taipei, Taiwan. SUBJECTS: Three hundred forty-six residents (ages, > or = 40 years) of Jin Shan Township. INTERVENTIONS: Whole-field scotopic testing, ophthalmoscopy with dilation of the pupils, cataract grading against photographic standards, and screening visual field testing in a random one-third subsample. MAIN OUTCOME MEASURES: Whole-field scotopic sensitivity (in decibels) and diagnostic status as a case of glaucoma, glaucoma suspect, or normal. RESULTS: Participants in Jin Shan Township did not differ significantly in the rate of blindness, low visual acuity, or family history of glaucoma from a random sample of nonrespondents. Scotopic sensitivity testing detected 100% (6/6) of subjects with open-angle glaucoma at a specificity of 80.2%. The mean +/- SE scotopic sensitivity for six subjects with open-angle glaucoma (32.78 +/- 1.51 dB) differed significantly from that of 315 normal individuals (38.51 +/- 0.22 dB), when adjusted for age and visual acuity (P = .05, t test). With linear regression modeling, factors that correlated significantly with scotopic sensitivity were intraocular pressure, screening visual field, best corrected visual acuity, presence of cortical cataract, and increasing age. CONCLUSIONS: Although cataract affects the whole-field scotopic threshold, it appears that scotopic testing may be of value in field-based screening for glaucoma.

Adult↗
PubMed2000

Converting visual acuity to utilities.

BACKGROUND: Utility theory can be used to quantify dysfunction associated with various diseases and thus can represent a "hard" measure of quality of life. By determining utility values, one can compare the quality of life of patients with ocular disease to that of patients with non-ophthalmic problems. We performed a study to determine whether utility values from patients with ocular disease are associated with clinical variables, including visual acuity in the better-seeing eye, and to develop a mathematical method for converting visual acuity to utility value, if there is an association between the two. METHODS: Cross-sectional study. A total of 239 patients from a tertiary care retinal practice with various ocular conditions, including macular degeneration, cataract, glaucoma and diabetic retinopathy, were interviewed under standardized conditions to determine their utility values by the time trade-off technique. Visual acuity, duration of visual loss and number of concomitant conditions were also determined. Multiple linear regression was performed to determine which variables were associated with utility values. RESULTS: The mean acuity in the better-seeing eye was 0.479 (near 20/40 vision). The mean utility value was 0.72. Accordingly, the average patient in our series was willing to trade 2.8 of every 10 remaining years of life to obtain perfect vision in both eyes. Utility value was significantly associated with visual acuity in the better-seeing eye (F = 69.1, p < 0.001). Other variables were not significantly associated with utility value. The association with duration of visual loss approached statistical significance (p = 0.075). Utility values (U) for patients with ocular disease can be derived from the following formula: U = (0.374)(visual acuity in better-seeing eye) + 0.514. INTERPRETATION: Utility values from patients with ocular disease were strongly associated with visual acuity and could be estimated mathematically.

Aged↗
PubMed1989

Quantitative visual psychophysics during the period of European enlightenment. The studies of the astronomer and mathematician Tobias Mayer (1723-1762) on visual acuity and colour perception.

During the sixth decade of the 18th century, Tobias Mayer, Professor of Astronomy and Applied Mathematics (Economy) at the University of Göttingen, performed two investigations on quantitative visual psychophysics. He deduced a power law for the dependence of visual acuity on the intensity of light by which the stimulus pattern was illuminated. In his measurements he compared visual acuity determined with single black dots and visual acuity measured with gratings or checkerboard patterns; the latter he considered as the "real" measurement of visual acuity. Mayer also developed a three-dimensional hexaedric colour space from the definition of subtractive colour mixtures of three primary pigments (red, yellow, blue). This colour space can be considered as the predecessor of the later colour tables of Ostwald and Munsell. Mayer gave a simple quantitative description of each of the 819 hues in his colour space. Both psychophysical studies developed out of Mayer's interest in practical problems in astronomy and cartography. Mayer's main scientific merits were in the field of astronomy and mathematical geography. His psychophysical studies were performed in the spirit of enlightenment with the a priori assumption that the performance of the human perceptual machinery can be measured quantitatively and that the results are adequately expressed by mathematical rules. Mayer's achievements in the fields of mathematics, physics, astronomy and cartography were recently summarized by the extensive historical research of G.F. Forbes. In the present report a short biographical note precedes the description of Mayer's psychophysical studies.

Astronomy↗
PubMed1991

Interrelations between measures of visual acuity and parameters of eye movement in congenital nystagmus.

The authors assessed relationships between visual acuity and the amplitude, frequency, intensity, and duration of foveation periods in a retrospective study of 32 patients. Twenty-four patients had congenital idiopathic nystagmus, and eight patients had nystagmus and albinism. Visual acuity was determined for Landolt ring optotypes and, as the extrapolated high-frequency cutoff of the contrast sensitivity function, for horizontal and vertical gratings. No significant correlation existed between acuity and any measured eye movement parameter; however, optotype acuity was related to the magnitude of astigmatic refractive correction, both in patients with idiopathic nystagmus and in albinos. In a subgroup of patients with idiopathic nystagmus whose astigmatic refractive error was -1.50 D or less, nystagmus intensity (amplitude x frequency) correlated significantly with acuity for optotypes (r = 0.71), but not for gratings. Although resolution for vertical gratings was correlated with astigmatic refractive correction, the ratio of resolution for gratings parallel and orthogonal to the meridian of nystagmus was not. Thus, the belief that poorer acuity in patients with substantial astigmatism is attributable to an optically induced meridional amblyopia is supported only partly by these results. The authors concluded that among patients with congenital nystagmus, the influence of eye motion on visual acuity is not readily predicted either from the parameters of nystagmus that they evaluated or from the comparison of resolution for horizontal and vertical gratings.

Albinism, Ocular↗
PubMed2005

Prevalence of visual acuity anomalies among pupils in age 7 and 8 years in Westpomeranian Region (Poland).

PURPOSE: Evaluation of visual acuity anomalies among 7 and 8 year olds pupils in Westpomeranian Region in the aspect of school nurses health services quality in that matter. MATERIAL AND METHODS: Representative sample (n=141) from the whole population of 7 and 8 years old pupils of Westpomeranian schools were screened for visual acuity with the use of Snellen standard boards. Classical methods for statistical analysis of results were used. RESULTS: 141 children were examined, among them 59 (42%) from urban areas and 82 (58%) from rural areas. The prevalence of abnormal visual acuity in general population of children in the age of 7 and 8 years in the region was estimated on the base of results from studied sample on the level of 17.7% +/- 5.0% for confidence interval 95% and was in the range 12.3-24.9%. CONCLUSIONS: High prevalence of visual acuity anomalies in general population of pupils (17.7 +/- 5.0%) indicates that more intensive preventive care is needed, also serving by school nurses. Precision in defining methodical approach in nursing care and procedure standards with respect to the affected pupils will result in improved preventive strategies.

Child↗
PubMed1990

The predictability of infant visual-evoked response testing on future visual acuity.

We reviewed the records of 27 infants with abnormal eye examinations and visual-evoked response (VER) testing (mean age, 10.5 months) who subsequently underwent a long-term follow-up ophthalmology examination (mean duration, 41 months). The infants were initially diagnosed with various ocular disorders including cortical blindness (eight), optic nerve hypoplasia (six), congenital cataract (two), and retinopathy of prematurity (one). Standard optotype visual-acuity determinations were available in the follow-up records of 11 children (21 eyes), and fixation behavior was obtained in the remaining 16 children (32 eyes). Results revealed that pattern-reversal VER P1 latency was predictive (87%) of whether visual acuity was equal to (or better than) or worse than 20/100 and whether a patient would have good fixation behavior (fix and follow, FF) or poor fixation (no FF) (86%) (P less than .001). Although flash VER P1 latency was also predictive of later visual acuity or good fixation (73%), it was not statistically significant. Pattern VER P1 amplitude and flash VER P1 amplitude were not predictive of later visual function. The predictive power of pattern VER P1 latency for later visual function probably relates to its reflection of macular function and low variability. An analysis of the variability of each of the four VER factors in normal infants (n = 50) indicated that pattern VER P1 latency was the least variable, and consequently most sensitive, VER factor for detecting and quantifying pathology. Overall, the results of this retrospective study suggest that pattern VER P1 latency may have important predictive power for later visual function in infants with an initially abnormal ophthalmologic examination.

Evoked Potentials, Visual↗
PubMedDate not supplied

Stability of refraction and visual acuity during 5 years in eyes with simple myopia. The PERK Study Group.

BACKGROUND: Normal ranges of variability of refraction and visual acuity in adult myopic eyes are needed as a reference standard for assessing the stability of refractive corneal surgery. METHODS: We measured the changes in spectacle-corrected visual acuity and cycloplegic refraction during 5 years for the unoperated eye of 82 patients aged 21 to 57 years in the Prospective Evaluation of Radial Keratotomy Study. The changes were compared for contact lens and non-contact lens wearers. We also compared the 5-year cycloplegic and manifest refractions for these unoperated eyes. RESULTS: Of 77 eyes, 44% gained or lost one Snellen line and 48% experienced no change in spectacle-corrected visual acuity between baseline and 5 years. Only one eye (1%) lost two lines, and 7% gained two lines. The refractive change was less than 1.00 D for 84% of the 37 non-contact lens wearing eyes. Only 13% became more myopic by at least 1.00 D (maximum increase in myopia, 2.00 D), and 3% became less myopic by 1.00 D. Of 45 contact lens wearing eyes, 38% became more myopic by at least 1.00 D. The 5-year manifest refraction was 0.50 D to 1.50 D more myopic than the cycloplegic refraction for 37% of eyes. CONCLUSIONS: We recommend using two or more Snellen lines as the standard for a meaningful change in spectacle-corrected visual acuity in operated eyes, and 1.00 D as a meaningful cutoff for stability of refraction. The wearing of contact lenses can confound the results of stability studies. The difference between the cycloplegic and manifest refractions suggests that the cycloplegic refraction should be used in planning for refractive surgery.

Adult↗
PubMed1984

Glare from outdoor high mast lighting: effects on visual acuity and contrast sensitivity in comparative studies of different floodlighting systems.

Glare effects on visual acuity and contrast sensitivity were studied at outdoor timber terminal work with conventional far-reaching floodlighting and with a new type of oblique floodlighting with an asymmetrical light distribution. The binocular work visual acuity of 19 volunteers was measured at 40, 55 and 80 per cent contrast and the contrast sensitivity of 14 volunteers at spatial frequencies of 0.5, 1, 2, 4, 8 and 16 cycles/degree. With the light source 15 degrees from the centre of the visual fields the visual acuity as well as the contrast sensitivity was consistently lower with the conventional type than the new type of floodlight . The results thus indicate that not only the vision of details is impaired by glare but also the contrast perception of sparse patterns. In standardized rating scales the timber terminal workers scored the difference in glare between the two floodlight systems as "great"--"very great".

Adult↗