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At least 919 records · Page 51Linked to original sources
PubMed1985

Visual acuity in a national sample of 10 year old children.

The prevalence of defects of visual acuity among the 10 year old children in the 1970 birth cohort was 22.1%, but only in one third of these children was the defect more severe than 6/9. Defects were more common among girls. The relation of defects to social class was complex. Comparison with data collected on the children of the 1958 cohort when they were 11 years old suggests that although the prevalence of 6/9 visual acuity has remained constant over the last decade, the prevalence of more severe defects has declined from 12.9% to 7.3%. These findings have a number of implications for the provision of screening programmes and of ophthalmic services for children.

Amblyopia↗
PubMed1979

Human visual acuity assessment through linear extrapolation to threshold of bar grating VERs.

Visual evoked responses (VERs) were obtained from seven normal eyes, using high contrast square-wave gratings of varying bar size on an 8 degrees or 24 degrees stimulus field. VER amplitude was plotted as a function of bar size. These plots, called square wave transfer functions (SWTFs), have one or more peaks when generated by a 24 degree field. In some individuals, the small bar size extreme of the function can be fitted well with a straight line for purposes of extrapolation to the visual acuity bar size. However, interindividual differences in the shape of the 24 degree field SWTF invalidates any a priori assumption of what bar sizes may be included in the extrapolation. Results from three subjects, using an 8 degree field, suggest that a more uniform single-peaked triangular SWTF with a peak near 5 min arc may be assumed for extrapolation purposes. The interindividual SWTF differences obtained with the 24 degree field were not random, the subjects falling into one of two groups on the basis of SWTF shape. This SWTF shape dichotomy may be correlated with the presence or absence of strabismus.

Adult↗
PubMed1989

The effect of increased intraocular pressure on visual acuity and corneal curvature after radial keratotomy.

To detect the effect of increased intraocular pressure on visual acuity and corneal curvature after radial keratotomy, we measured these variables in the sitting and inverted positions in 18 patients who underwent radial keratotomy (Group 1) and compared their results with those from the unoperated on eyes of seven patients (Group 2). We also compared the results before and after inversion within each group. Intraocular pressure increased to approximately two times normal in each group. Significant improvement in visual acuity and reduction in central keratometry were noted only in Group 1. By multiple regression analysis, visual improvement correlated with the number of incisions but not the time since surgery. Our study provides evidence that increased intraocular pressure may account for transient changes in vision and corneal curvature after radial keratotomy.

Adult↗
PubMed1990

Visual acuity in a prison population.

I determined the best corrected acuity of 90 prisoners. The data were compared to available published visual acuity data for the general population and to 6/6 (20/20) as the assumed normal. The prison population differed significantly from the population analyzed in one reported study but not from that in another (p less than 0.05). Comparison to the assumed normal of 6/6 showed no statistical difference. The differences among the studies are discussed. The data suggest that for this population corrected visual acuity may not be dissimilar from that of the general population.

Humans↗
PubMed1985

A distance visual acuity chart incorporating some new design features.

Standardized visual acuity assessments are possible when consideration is given to legibility, acuity row legibility, letter spacing, optotype, row arrangement, and letter size gradation. The relative optotype legibilities reported by Sloan were verified experimentally under simulated conditions of optical defocus. Acuity row component letters were selected to equalize aggregate row legibilities and were arranged to minimize contaminative sequencing dependency. We describe a new acuity chart format with vertical acuity row presentations to eliminate bias from previous reading experience, and testing procedures using this chart.

Humans↗
PubMed1987

Reporting the visual acuity of groups: the relation among alternate measures.

There are often large disparities in the way in which visual acuities are reported for groups. A survey of 156 reports published within the last 5 years shows that some researchers report binocular acuity, others best eye, monocular, or mean monocular acuities. Some of these measures may be confounded further with accommodation distance. To ascertain the relation among the various measures of acuity reported commonly, data were obtained from 702 observers. The results indicate that there is a high degree of concordance among the various measures used to report the visual acuity of groups, with many of the correlations in the 0.9 range. It is further shown that a composite measure, based upon mean binocular or best eye acuity, may be a useful means of conveying group differences in visual resolution.

Adolescent↗
PubMed1985

Long-term effects of extended wear lenses: changes in refraction, corneal curvature, and visual acuity.

Extended wear lenses (Scanlens 75) +4.25 to -10.00 D were worn monocularly by 19 patients for an average of 5.4 years. The other eye of each patient was either emmetropic or amblyopic and no lens was worn. Both eyes were tested after lens removal and again 2 days and 7 days later. No significant differences in refraction, keratometry, or visual acuity were found between the experimental and control eyes. The amount of changes in both groups was not clinically significant: refractive changes averaged less than 0.37 D, keratometric changes averaged an equivalent 0.25 D, astigmatism increases were less than 0.25 D, and visual acuity was fully correctible to previous best visual acuity with spectacles in all cases.

Adolescent↗
PubMedDate not supplied

[Automated instrument for determining visual acuity].

The developed APZ instrument, due to a high degree of its automation, allows examination of visual acuity within minimum time spent by the physician. This procedure can be made in conditions of individual visit and mass-screening of patients. Measurement's limits age from 0.1 to 2.2. The visual acuity check-up can be performed automatically on a present program, or remotely by a physician. The APZ-I will find its application among instrumentation of ophthalmological cabinets in polyclinics, hospitals, medical centres, in special cabinets, etc.

History of Medicine↗
PubMed1982

Visual acuity after surgery for retinal detachment with macular involvement.

The records for a group of 2,054 patients who had undergone surgery fur rhegmatogenous retinal detachment with macular involvement were analyzed to ascertain the relative influence of the following five specific factors on postoperative visual acuity: (1) patient age, (2) degree of preoperative macular elevation, (3) duration of preoperative macular detachment, (4) extent of retinal detachment, and (5) drainage of subretinal fluid. Increasing patient age, increasing preoperative macular elevation, increasing duration of macular detachment, and increasing extent of retinal detachment were all found to be associated in general with decreasing postoperative visual acuity. Drainage, or nondrainage, or subretinal fluid appeared to be unassociated with postoperative visual acuity.

Adult↗
PubMed1985

Visual acuity of infants and children with retinal degenerations.

Visual acuity for gratings was studied in 18 infants and children with generalized retinal degenerations using preferential looking (PL) procedures. Diagnoses were Leber's congenital amaurosis (12), Laurence-Moon-Bardet-Biedl-like syndromes (4) and metabolic disorders (2). ERG's were extinguished in 11 patients and much attenuated in seven patients. Acuities at all ages (two months to 12 years) were significantly poorer than normal, and patients with extinguished ERG's had the poorest acuity. Neurological abnormality or mental retardation, present in ten patients, was as likely in patients with 6/60 or poorer grating acuity as in patients with better than 6/60 acuity. A comparison group of 12 infants and children with oculocutaneous albinism showed significantly better grating acuities than the patients with retinal degeneration. Relatively good grating acuity in infants with no anatomic fovea (oculocutaneous albinism) and much poorer acuities of infants with generalized retinal degeneration suggest that parafoveal or peripheral retina is necessary and sufficient for normal, behaviorally-obtained grating acuity in infancy.

Adolescent↗
PubMed2006

Deterioration of visual acuity associated with growth hormone therapy in a child with extreme short stature and high hypermetropia.

BACKGROUND: Growth hormone (GH) has long been implicated in the pathogenesis of diabetic retinopathy, although its precise role remains ill-defined. In 1998, an association between exogenous human GH and retinal pathology in non-diabetic subjects was described. CASE REPORT: A female child with extreme short stature of unknown aetiology (height -7.38 SD at 11.3 years) and severe hypermetropia developed retinopathy with visual deterioration during two separate empiric trials of GH therapy. On the first occasion, a relatively high dose of GH (10.5 mg/m2/week) administered from age 4.4 to age 4.7 years was associated with the development of central serous retinopathy, resulting in marked reduction in visual acuity. On cessation of GH, the macular oedema resolved, and visual acuity improved. At age 5.6 years, GH therapy was re-introduced at a lower dose (3.9 mg/m2/week) and her vision monitored closely. Bilateral retinal oedema recurred after 3 months, and GH therapy was stopped. Once again, the macular oedema regressed, and visual acuity improved following withdrawal of GH. These ophthalmic changes contra-indicated further GH therapy. CONCLUSION: We suggest that GH may be a risk factor in the development of retinopathy in certain non-diabetic patients, especially in the presence of a severe refractive error.

Child↗
PubMed2002

Hypotonous maculopathy and normal visual acuity secondary to post-traumatic cyclodialysis cleft.

BACKGROUND: Post-traumatic cyclodialysis clefts commonly lead to profound visual loss secondary to hypotonous maculopathy. Current literature regarding cyclodialysis clefts definitively outlines the management of visual loss resulting from hypotonous maculopathy. Because hypotonous maculopathy with normal visual acuity is rarely reported, management is less well defined. Management guidelines for individuals with and without visual loss secondary to hypotonous maculopathy are reviewed. CASE REPORT: A 32-year-old man came to us with symptoms of blur and glare in his left eye following airbag trauma two-and-a-half years earlier Best-corrected visual acuities measured 20/15 O.D. and O.S. A small iris sphincter tear was noted inferiorly and gonioscopic evaluation revealed a corresponding cyclodialysis cleft O.S. Intraocular pressures measured 10 mmHg O.D. and 2 mmHg O.S. Funduscopic evaluation of the left eye reveal optic disk edema, chorioretinal folds within the papillomacular bundle, venous tortuosity, and peripheral hemorrhages. Anticholinergic therapeutic management for hypotony was unsuccessful. Surgical intervention was not recommended. Visual function remains unchanged. CONCLUSION: Identification of a cyclodialysis cleft is imperative after blunt trauma. Therapeutic and/or surgical intervention remains the treatment of choice when hypotonous maculopathy affects visual outcome. Conservative management may be indicated in those cases in which visual function is not impaired.

Adult↗
PubMed1997

The visual acuity of the frog (Rana pipiens).

The frog's visual acuity for gratings was tested with a two-choice prey-dummy setup. The two dummies had a constant position in the visual field, but in one of them a striped pattern was constantly drifting, while the other was a potentially less attention arousing dummy with non-moving stripes. The acuity was tested in bright white light and with different brightness levels of green light (500 nm). The highest acuity 2.8 cycles per degree was achieved with the maximum level of green light. When the brightness was lowered by six orders of magnitude the acuity fell to 0.7 cycles per degree. These behavioural acuities are compared with a theoretically calculated resolving power of the retinal ganglion cell array.

Animals↗
PubMed1990

Idiopathic photoreceptor dysfunction causes unexplained visual acuity loss in later adulthood.

Progressive visual loss, caused by initially unrecognized retinal photoreceptor dysfunction predominantly affecting cones, developed in six patients in late adulthood. Because of minimal ophthalmoscopic retinal abnormalities, the patients initially had been suspected of having optic neuropathy or psychogenic visual loss. The correct diagnosis was ultimately established by finding electroretinographic abnormalities and color discrimination losses out of proportion to visual acuity loss. In no case was a causative agent or a family history of photoreceptor disease identified. In many other respects, however, features of the patients' illness resemble those described previously under the headings of cone dysfunction syndrome, cone dystrophy, cone degeneration, and cone-rod dystrophy.

Aged↗
PubMed1966

Human visual acuity measured with colored test objects.

Visual acuity was measured with a grating test object in which alternating bars were matched in brightness but differed in wavelength. If the wavelength difference between adjacent bars was great enough, acuity scores were obtained which were as high as those obtained with test objects in which there was a large brightness difference between adjacent bars.

Color↗
PubMed2003

Optotype and grating visual acuity in preschool children.

PURPOSE: To investigate the contribution of stimulus and response differences to the different developmental courses of grating and optotype visual acuity at the preschool age range. METHODS: Binocular visual acuity at 228 cm was assessed in 205 children in 7 age groups between 2.5 and 6 years and in 12 adults. Acuities were obtained in three tasks: detection of a grating in one of two positions, discrimination of the orientation of a single grating, and discrimination of the orientation of the gap in an uncrowded Landolt-C optotype. The three paradigms were as similar as possible in stimulus contrast, luminance, presentation mode, and psychophysical procedure. RESULTS: Mean grating and optotype acuities were lower than adult acuities at all ages. Optotype acuity was overall higher and increased faster with age than grating acuities. Grating orientation acuity was slightly but not significantly lower than grating detection acuity in all but one age group. The grating detection task was successful at earlier ages (100% at 3.5 years) than both the optotype acuity task (100% at 4.5 years) and the grating orientation task (100% at 5.75 years). CONCLUSIONS: Optotype and grating acuities follow a different developmental course in children between 3 and 6 years of age, with optotype acuity growing superior to grating acuity in that age range. The similarity of grating orientation to grating detection acuities and the difference between grating and optotype acuities suggest that superior optotype acuity is due to stimulus characteristics rather than to the complexity of the response required.

Adult↗
PubMed1986

Testing visual acuity in the emergency department: a simple method of correcting refractive error by using the hand-held ophthalmoscope.

The assessment of visual acuity is an important part of the emergency ophthalmologic examination. The ability to distinguish refractive error from other etiologies of decreased visual acuity is necessary to adequately evaluate visual function. A readily available source of corrective lenses can be found in the hand-held ophthalmoscope. These lenses can be used to identify and quantitate refractive errors and assist in identifying serious ocular pathology.

Emergencies↗