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Results for “Visual Acuity”

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At least 541 records · Page 30Linked to original sources

PubMed1997

Disparity between refractive error and visual acuity after photorefractive keratectomy: multifocal corneal effects.

PURPOSE: To determine the relationship between postoperative refractive error and uncorrected visual acuity (UCVA) after photorefractive keratectomy (PRK) and compare the results to those in unoperated control eyes with different degrees of myopic refractive error. SETTING: Academic cornea and refractive surgery subspecialty practice. METHODS: Uncorrected visual acuity and manifest refraction were recorded for 52 consecutive patients who had PRK for myopia. Eight control eyes that did not have PRK and in which artificial myopia was induced were also studied to ascertain the association of UCVA with myopia in untreated eyes. Uncorrected visual acuity in postoperative eyes was compared with that in control eyes. RESULTS: Of the 46 eyes with a myopic spherical equivalent postoperative refraction, 44 (96%) had better UCVA than control eyes with equivalent myopic refractions. Twelve of 13 (92%) eyes with refractions of -1.00 diopter or more had a UCVA of 20/40 or better. CONCLUSION: After excimer laser PRK, patients achieved better Snellen visual acuity than might be expected from their residual refractive error, perhaps as a result of a multifocal postoperative corneal topography. Nonuniformity of the corneal surface following PRK may create "focal areas of emmetropia" that allow patients to achieve better visual acuity than the refraction may predict.

Adult↗

PubMed1998

Visual acuity and its relationship to early growth, eye disease, and aging in north Hertfordshire.

We investigated the relationship between visual acuity, early growth and eye disease in a retrospective cohort study of 700 individuals in North Hertfordshire. Records of birth weight and weight at one year were used to determine early growth. We measured visual acuity and age-related eye diseases using standard instruments in those same individuals (now aged 63 to 73). Visual acuity below the legal threshold for driving in the UK (6/11 or poorer) was present in 13% of subjects. There was no clear association between birth weight or weight at one year and visual acuity. Vision impairment was found to be associated with refractive error, cataract, age-related maculopathy, and elevated macular threshold. After controlling for the effects of eye disease, increasing age remained a significant predictor of poorer visual acuity.

Aged↗

PubMedDate not supplied

[Visual acuity and astigmatism after eccentric penetrating keratoplasty - a retrospective study on 117 patients].

PURPOSE: The purpose of this study was to asses the functional results of eccentric homologous penetrating keratoplasty in respect of diagnosis as well as position and size of the corneal graft. PATIENTS AND METHODS: In this retrospective study, visual acuity and astigmatism of 117 cases of a round eccentric homologous penetrating keratoplasty in 91 eyes of 91 patients were analysed. The PK became necessary because of a corneal ulcer (104), 6 eyes with corneal scars and 7 eyes with ectatic corneal diseases. Using 84 postoperative slides the following parameters were quantified: graft diameter and transparency, distance of the geometric centre of the cornea from the central trephination margin (distance) as well as from the geometric centre of the graft (decentration). Seventeen grafts were classified as eccentric peripheral keratoplasty (mean diameter 5.0 +/- 1.7 mm) with the optical axis through the host cornea and 67 as eccentric central keratoplasty (7.0 +/- 1.3 mm) with the optical axis through the graft. RESULTS: The average follow-up period was 25 months. The astigmatism after 3/12/24 months was 6.7/6.3/5.5 D, but was irregular and not measurable in 74 %/52 %/49 %. The astigmatism increased with increasing decentration (24 months, p = 0.04). After 3/12/24 months, the VA in ulcers was 0.1/0.16/0.16, in scars 0.2/0.6/0.5 and in ectatic diseases 0.3/0.5/0.6. The position of graft and the visual acuity did not correlate significantly. After 24 months, larger the graft size was associated with better visual acuity. With increasing decentration the visual acuity decreased (p = 0.02) and was significantly lower (0.15) in the case of - 2.0 < distance < 2.0 mm than in the case of distance > 2.0 mm (0.4; p = 0.01). CONCLUSION: The diagnosis resulting in eccentric penetrating keratoplasty seems to have a major impact on the long-term functional prognosis of visual acuity. In addition, visual acuity is limited by high and often irregular astigmatism. Our results indicate that an increasing decentration of the graft is not invariably associated with decreasing visual acuity, provided the graft-host junction is not located in direct proximity of the optical axis.

Adolescent↗

PubMed2000

Visual acuity measurements in a national sample of British elderly people.

BACKGROUND: Despite the fact that visual function has an important role in the quality of life in later years, very few studies have measured visual acuity in population based nationwide samples of British elderly people. Such measurements were carried out in the context of the national diet and nutrition survey of people aged 65 years or over (NDNS). METHODS: NDNS participants, who were living in 80 different randomly selected postcode areas of mainland Britain, were visited at their home by a nurse who measured visual acuity at 3 metres, using the Glasgow acuity card (GAC) method. In addition, a brief questionnaire related to ocular health was administered. RESULTS: Visual acuity was measured in 1362 NDNS participants who were not classified as mentally impaired. Visual impairment (using the WHO low vision criteria) was measured in 195 (14.3%) subjects. Prevalence of visual impairment increased significantly with age (65-74 years 3.1%; 75-84 years 11.6%; 85+ years 35.5%, p<0.001 for trend). Impaired vision was more common in subjects living in a nursing home (odds ratio adjusted for age 2.59 (95% CI 2.23 to 2. 96)) and in women (odds ratio adjusted for age 1.55 (95% CI 1.21 to 1.89)). 132 (9.7%) subjects had previously undergone cataract surgery and another 157 (11.5%) had been told that they currently had cataract. Vision improved 0.2 log units or more (at least one Snellen line) with the aid of a pinhole occluder in 289 subjects (21. 2%). CONCLUSION: Results of this nationwide, community based study confirm that problems with poor distance visual acuity exist in a substantial part of the elderly community, particularly in women and people living in nursing homes.

Aged↗

PubMed1979

Residual astigmatism and visual acuity with hydrogel contact lenses: a comparative study.

Residual astigmatism, visual acuity, and transferred corneal toricity were measured in a double masked fashion on 24 randomly selected patients fitted with Buasch and Lomb Soflens contact lenses, the Hydrocurve II contact lenses, and the AOSoftTM hydrophillic contact lenses. None of the subjects had any contraindications to hydrogel lens wear. All three lens types produced a small but similar reduction in refractive astigmatism. However, because of residual astigmatism, fewer eyes achieved 20/20 or better visual acuity with each of the hydrogel lens types than with the best spectacle correction. Corneal toricity was found to be transferred to the front surface of all three lens types. Our findings indicate that generally these three types of hydrogel lenses result in similar residual astigmatism, visual acuity and transferred corneal toricity. However, individual differences may occur. Therefore, the choice of lens type should be based on the individual patient's response to various lens types.

Adult↗

PubMed2004

Charles Bonnet syndrome and visual acuity--the involvement of dynamic or acute sensory deprivation.

A 61-year-old patient suffered from Charles Bonnet syndrome (CBS) while his visual acuity declined, whereas CBS subsided after he became blind. These findings suggest that reduction of visual acuity (dynamic or acute impairment) has a greater impact on the onset of CBS than low visual acuity (static or chronic impairment) per se in some patients. They may also explain why patients with low visual acuity do not always suffer from CBS. Although further studies are required, the present case highlights the importance of the differentiation between lowering and low visual acuity in the etiology of CBS.

Humans↗

PubMed1996

Multicenter trial of cryotherapy for retinopathy of prematurity. Snellen visual acuity and structural outcome at 5 1/2 years after randomization.

OBJECTIVE: To evaluate outcome at 5 1/2 years after randomization in eyes that underwent cryotherapy and in control eyes of patients in the Multicenter Trial of Cryotherapy for Retinopathy of Prematurity. DESIGN: During infancy, patients with bilateral threshold retinopathy of prematurity (ROP) were assigned to receive cryotherapy for one eye and no cryotherapy for the other eye. Those with threshold ROP in only one eye (asymmetric) were randomly assigned to cryotherapy or no cryotherapy for that eye. Then, 5 1/2 years later, testers who were masked to the treatment status of each eye measured the patients' monocular visual acuity by using the log of the minimum angle of resolution visual acuity chart that was used in the Early Treatment of Diabetic Retinopathy Study. This was the most refined visual acuity testing yet performed on this cohort. Structural outcome was evaluated by participating ophthalmologists' assessment of ROP residua in the posterior pole of the fundus. PATIENTS: Patients were 291 children who had been preterm infants with birth weights of less than 1251 g in whom threshold ROP had developed. Two hundred forty patients had bilateral threshold ROP, and 51 had threshold ROP in only one eye. RESULTS: For the 234 children examined, both visual acuity and fundus structure showed a reduction in unfavorable outcomes in treated vs control eyes: 47.1% vs 61.7%, respectively (P<.005), for visual acuity and 26.9% vs 45.4%, respectively (P<.001), for fundus status. Detailed analysis of visual acuity outcomes for all eyes revealed that while fewer treated eyes (31.5%) than control eyes (48%) were blind (P<.001), there was a slight trend toward fewer eyes with a visual acuity of 20/40 or better in the treated (13%) vs control (17%) groups (P=.19). CONCLUSIONS: The results support the long-term efficacy and safety of cryotherapy in the treatment of severe ROP. However, the data show preliminary evidence of a possible adverse effect of this treatment on visual acuity.

Child↗

PubMed1986

Visual acuity loss in patients with Usher's syndrome.

Using a life-table analysis, visual acuity loss with age was determined for a population of 106 patients with type 1 (N = 35) and type 2 (N = 71) Usher's syndrome. The cumulative percentage of patients maintaining visual acuity of 6/12 (20/40) or better in at least one eye by age 29 years was 69% for type 1 patients and 94% for type 2 patients. The cumulative percentage maintaining visual acuity of 6/24 (20/80) or better at this age was 89% for type 1 and 98% for type 2 patients. Within each subtype, the cumulative percentage maintaining 6/60 (20/200) or better was similar to the percentage maintaining 6/24 (20/80) or better. Knowledge of these data provides an objective basis for counseling patients with Usher's syndrome about their probability of developing loss of central visual acuity with age.

Actuarial Analysis↗

PubMed2004

Endophthalmitis after pars plana vitrectomy: Incidence, causative organisms, and visual acuity outcomes.

PURPOSE: To investigate the incidence, causative organisms, and visual acuity outcomes associated with endophthalmitis after pars plana vitrectomy. DESIGN: Retrospective, noncomparative, consecutive case series. METHODS: The medical records were reviewed of all patients who developed acute-onset postoperative endophthalmitis (within 6 weeks of surgery) after pars plana vitrectomy at Bascom Palmer Eye Institute between January 1, 1984 and December 31, 2003. RESULTS: During the 20-year study interval, the overall incidence rate of postvitrectomy endophthalmitis was 0.039% (6/15,326). Cultured organisms were Staphylococcus aureus (n = 3), Proteus mirabilus (n = 1), and Staphylococcus epidermidis/Pseudomonas aeruginosa (n = 1); one case was culture-negative. Visual acuity after treatment for endophthalmitis ranged from 2/200 to no light perception, with a final vision of light perception or no light perception in four of six (67%) eyes. CONCLUSION: The incidence of endophthalmitis after pars plana vitrectomy is low but the visual acuity outcomes after treatment are generally poor.

Acute Disease↗

PubMed1998

Effect of formula supplemented with docosahexaenoic acid and gamma-linolenic acid on fatty acid status and visual acuity in term infants.

BACKGROUND: Docosahexaenoic acid is present in high concentration in retina and does not influence visual development in preterm infants. It is still under discussion whether docosahexaenoic acid is important for visual development in term infants. METHODS: Thirty-seven infants fed formula for a median of 14 days were randomized at median age of 25 days to three formulas: a) DHAGF: 0.3 wt% docosahexaenoic acid and 0.5 wt% gamma-linolenic acid; b) DHAF 0.3 wt% docosahexaenoic acid; or c) STF: standard formula without long-chain polyunsaturated fatty acids and 17 breast-fed infants were observed, using blood samples and anthropometric measurements from 1 to 4 months of age. At 4 months, visual acuity was measured by swept steady-state visual evoked potential. A cross-sectional study on 25 breast-fed infants was carried out as a reference group for the analyses. RESULTS: Infants fed the two docosahexaenoic acid-supplemented formula had relative docosahexaenoic acid concentrations in red blood cell phospholipids almost as high as those in breast-fed infants, whereas infants in the standard formula group had significantly lower levels. The addition of gamma-linolenic acid to the formula had a positive effect on red blood cell arachidonic acid levels, compared with levels obtained using fish oil only. Visual acuity was significantly different among all feeding groups (analysis of variance; p = 0.05, means +/- standard deviation: breast-fed, 0.37+/-0.06 logMAR; DHAF and DHAGF combined, 0.40+/-0.07 logMAR; and standard formula 0.44+/-0.07 logMAR. However, there was no statistical difference among the formula groups. In a multiple regression analysis including all formula-fed infants, weight at delivery (p = 0.002), but not type of formula, was significantly associated with visual acuity at 4 months of age. CONCLUSIONS: The addition of docosahexaenoic acid resulted in concentrations in red blood cells at similar levels as those in breast-fed infants, whereas the increase in visual acuity did not reach significance. The addition of gamma-linolenic acid resulted in higher arachidonic acid concentrations in red blood cells.

Anthropometry↗

PubMed1989

[Measurement of visual acuity in infants in 6 minutes: Teller's Acuity Cards].

Most of the development of infant visual function occurs during the first year of life. Early pathological symptoms affecting visual or oculomotor processes, particularly ocular misalignment or amblyopia, should be detected and treated at the earliest age. Orthoptic and ophthalmological tests have been available for a long time but there remained a need for a convenient test for measuring visual acuity. Preferential looking techniques fulfill this demand and have been proven reliable and convenient to estimate visual acuity in preverbal infants. A new commercial presentation of the test, called Teller Acuity Cards, is described. Testing an infant was rapid, 5 to 6 minutes for a normal child, and easy because the child enjoys the convivality of the situation. Space requirement is reduced. Measures were taken from a population of 50 normal children aged 4 to 12 months. All children responded in the three situations, binocular and monocular (there was no blind eye in the group). Grating acuity values were higher than those obtained by projection preferential looking techniques. Binocular acuity was 6.5 cycles/deg (approximately 2.5/10) at 4 months of age, 9.8 cycles/deg (approximately 3.3/10) at 9 months and up to 13 cycles/deg (approximately 5/10) around 12 months. Acuities were found to be half an octave lower in monocular condition as compared to binocular. Orthoptic and ophthalmological check-up of infants is important, especially in case of children at risk of visual disorder. In most instances acuity can be preserved by therapeutic action provided it is initiated during the first year of life, when sensitivity to appropriate stimulation is at its peak.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗

PubMed1989

Effect of defocus on visual acuity as measured by source and observer methods.

The relation between refractive error and visual acuity has been measured by two very different methods. In one called "source methods," emmetropes or corrected ametropes view defocused stimuli presented on projection screens or photographs. In the type called "observer methods," focused stimuli are presented to the observers who are either uncorrected ametropes or emmetropes defocused by lenses placed (usually), in the spectacle plane. The study reported in this paper demonstrates for the first time that these two methods of defocusing retinal images and their effects on visual acuity can be correlated. Results show that the source method of producing defocus could be used interchangeably with the observer method in investigating the rates of change of visual acuity with defocus for young normal observers. The angular diameter of the defocused image of a point, the blur disc diameter in object space, allows the two methods to be compared. Although the results show that the two methods are highly correlated, they show that the source method gives a statistically but not clinically significant lower acuity. The results of both methods are used to derive an equation linking refractive error, visual acuity, and pupil diameter.

Accommodation, Ocular↗

PubMed2003

Distance visual acuity impairment and survival in African Americans and non-Hispanic Whites.

BACKGROUND: Regional studies conducted in the United States have shown associations between visual impairment and shorter survival in non-Hispanic Whites. OBJECTIVE: To examine associations between visual impairment and mortality in a nationally representative sample of African Americans and non-Hispanic Whites residing in the United States. DESIGN: Mortality linkage with participants from the 1974-1975 National Health and Nutrition Examination Augmentation Survey was performed by the National Center for Health Statistics in 1992. SUBJECTS: Complete data were available on 245 African Americans and 2571 non-Hispanic Whites. METHODS: Uncorrected binocular distance visual acuity was assessed using Sloan letter charts. Usual-corrected visual acuity was then obtained with participants wearing glasses or contact lenses, if any. Analytical methods included Cox regression models with adjustment for sample weights and design effects as well as age, gender, smoking status, and self-rated health. RESULTS: Multivariate survival analyses found a significant interaction between race and visual impairment status; consequently, race-specific analyses were performed. There were no significant associations between uncorrected binocular visual acuity impairment (20/50 or worse) and all-cause mortality or cancer mortality. There was no significant association between impaired uncorrected acuity and cardiovascular disease mortality in African Americans (Hazard Ratio=0.67, 95% CI: 0.35-1.26), but this association was significant in non-Hispanic Whites (Hazard Ratio=1.21, 95% CI: 1.01-1.45). In multivariate models, within race groups, impaired usual-corrected visual acuity was not associated with an increased risk of all-cause mortality or mortality due to cancer or cardiovascular disease. CONCLUSIONS: Uncorrected and usual-corrected binocular distance visual impairment is not associated with all-cause mortality or cancer mortality. Cardiovascular disease mortality risk may be slightly higher in non-Hispanic Whites with uncorrected visual acuity impairment.

Black People↗

PubMed1987

[Contour interaction in the examination of visual acuity].

The author discusses the problem of the interoptotype distance in visual acuity charts. A small interoptotype distance (5,5' minutes) kept constant throughout the chart enhances the sensitivity of the visual acuity measurement for the detection of a functional deficit, without decreasing its specificity. A specification of the distance between the last recognized optotypes should be given with the visual acuity in order to permit an estimate of the measurement's validity. A simple formula for the measurement in minutes of the angular interoptotype distance is presented.

Adolescent↗

PubMed1996

Prediction of visual acuity after early vitrectomy in diabetics.

In proliferative diabetic retinopathy the indication of early vitrectomy remains controversial. At present, no decision rule exists for the assessment of the various factors predicting the postoperative visual outcome. We reviewed 75 vitrectomies in 68 diabetics from our clinic. All vitrectomies were done by one surgeon. In all cases, vitrectomy was indicated because of nonclearing vitreous hemorrhage and/or fibrovascular proliferation. A linear regression model was used to identify factors correlating with the visual outcome. By means of univariate analysis, six of nine clinical variables were found to be associated with the final visual outcome. Dividing the patients into two groups according to their preoperative visual acuity (group 1 hand movement, group 2 better than hand movement), we identified two predictors that were independently associated with the postoperative visual acuity: group 1-the visual acuity of the fellow eye (P < 0.05) and rubeosis iridis (P < 0.05); group 2-the visual acuity of the fellow eye (P < 0.001) and preexisting systemic diabetic vascular disorders (P < 0.01). Based on this model, a formula was derived to predict the visual acuity at 6 months postsurgery. For easier handling the prognostic factors of a poor visual outcome (less than 0.1) were summarized in a flow chart. The test is a useful tool for the preoperative evaluation of various risk factors and, hence, for more reliable prediction of a poor visual outcome. Thus, it may be especially useful to objectify the risk-benefit ratio for early vitrectomy in diabetics.

Diabetic Retinopathy↗

PubMed1986

Refractive error and preferential looking visual acuity in human infants: a pilot study.

A clinical pilot study comparing refractive error and preferential looking (PL) visual acuity in infants 2 to 12 months of age is described. The PL visual acuity of 30 normal infants without significant visual disorders was assessed using the Acuity Card Procedure. Near retinoscopy was used to determine refractive error. Infants of this sample had monocular PL visual acuities similar to those established by McDonald et al. in a laboratory setting. Statistical analysis of the data for this sample of infants showed that refractive error did not change systematically from 2 to 12 months of age. We have found that results obtained with the Acuity Card Procedure in a clinical setting agree with infant visual acuity as described in the research literature. Refractive error did not correlate with changes in PL visual acuity in infants 2 to 12 months of age.

Humans↗

PubMedDate not supplied

Prediction of spectacle-corrected visual acuity using videokeratography.

PURPOSE: Our aim was to improve prediction of spectacle-corrected visual acuity (SCVA) using indices derived from the EyeSys System 2000 data (version 3.1). METHODS: We studied corneal topography in 182 eyes from 8 groups of patients. Holladay Diagnostic Summary indices were recorded. Nine statistical indices calculated with the first 8-ring data and refractive power symmetry index were also studied. Correlation with SCVA (LogMAR units) was studied by means of Pearson's regression. Multiple linear regression was used to obtain linear equations combining several indices. RESULTS: At a univariate level, total astigmatism cylinder showed the strongest correlation with SCVA (r = .63, P = .0001). At a multivariate level, the predicted visual acuity obtained by linear equation combining the asphericity coefficient, the predicted corneal acuity, the mean of the means, and the total astigmatism cylinder was closely associated with SCVA (r = .72, P = .0001). It was identical to SCVA in 58.2% of the cases, within one line in 75.8%, and within two lines in 91.2%. CONCLUSION: Multiple linear regression resulted in the best prediction of spectacle-corrected visual acuity, giving notable improvement in prediction of spectacle-corrected visual acuity as compared to the predicted corneal acuity available in the EyeSys System 2000.

Astigmatism↗

PubMed1999

[Entoptic phenomena and potential visual acuity].

REVIEW OF PREOPERATIVE EVALUATION OF VISUAL FUNCTION: In the presence of media opacities, the prevision of the potential postoperative visual acuity constitutes often a complicate diagnostic problem. Its solution requires the experience of the ophthalmologist, who should take into account various elements from the patient's visual aggravation progress, the dissociation between far and near vision under mesopic and scotopic conditions, the actual grating acuity and the eventual hand movement and light-perception, as well as, elements from the patient's objective examination, i.e., from the biomicroscopy with direct and indirect illumination through the still transparent media and from the binocular ophthalmoscopy of the fundus. METHODS REVIEWED: Purkinje figure and luminous darting points visualization. POSSIBLE PREDICTIONS: Light induced entoptic imagery, as Purkinje figure and luminous darting points, visualization, helps as a supplementary diagnostic procedure, for the prevision of a low, but socially useful postoperative visual acuity.

Humans↗