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Results for “Visual Acuity”

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At least 451 records · Page 25Linked to original sources

PubMed2006

Objective measurement of visual acuity by optokinetic response determination in patients with ocular diseases.

PURPOSE: To investigate the efficacy of optokinetic nystagmus (OKN) suppression and induction methods for the objective estimation of visual acuities in patients with various ocular diseases. DESIGN: Prospective, descriptive study. METHODS: One hundred seventy-three eyes of 89 patients aged between 27 and 75 years who registered at our institution from January to December 2004 were prospectively enrolled onto this study. Ocular diseases included generalized retinal diseases (47 eyes), media opacity (32 eyes), refractive errors (31 eyes), glaucoma (27 eyes), maculopathies (26 eyes), and optic neuropathies (10 eyes). Horizontal optokinetic stimuli were presented on a 17-inch monitor screen at a distance of 40 cm from the subject in a dark room. Horizontal eye movements were recorded in each eye separately by infrared oculography. Objective visual acuities measured by using OKN suppression or induction methods were compared with subjective visual acuity assessments. The logarithm of minimal angle of resolution visual acuity was 1.03, and ranged from -0.08 to hand movement. RESULTS: Linear regression identified minimum stripe stimuli required to induce OKN by using the OKN induction method, and the minimum dot size required to suppress OKN was found to be correlated with subjective visual acuity (P<.01). The induction method was useful in patients with visual acuities of 20/60 or worse, and the suppression method was useful in patients with visual acuities of 20/200 or better. CONCLUSIONS: Combined use of the OKN induction and suppression methods provides a satisfactory means of determining objective visual acuity.

Adult↗

PubMed2004

Acute severe visual acuity decrease after photodynamic therapy with verteporfin: case reports from randomized clinical trials-TAP and VIP report no. 3.

PURPOSE: To describe in detail occurrences of acute severe visual acuity decrease after photodynamic therapy (PDT) with verteporfin in the Treatment of Age-related macular degeneration with Photodynamic therapy (TAP) Investigation and the Verteporfin In Photodynamic therapy (VIP) Trial. DESIGN: Observational case series. METHODS: Retrospective review of all cases that developed acute severe visual acuity decrease after treatment. RESULTS: Of 15 acute severe visual acuity decrease events originally identified in 14 eyes of 14 patients, one event in one patient was judged unlikely to have been an acute severe visual acuity decrease event on retrospective review of these events in preparation of this report. Eleven events occurred after the first treatment. At follow-up, 10 improved by at least 1 line in visual acuity from the level noted at the time of the event. Of the nine patients returning for the month 24 examination, visual acuity decreased at least 3 lines from baseline in six, including at least 6 lines in four, and remained within 1 line in three. Associated abnormal morphology included three with a serous macular detachment and abnormal choroidal hypofluorescence, four with macular hemorrhage, three with a greenish subfoveal hemorrhage, and four with no abnormality. Events appeared to be more likely when patients had a visual acuity of 20/50 or better. CONCLUSIONS: Acute severe visual acuity decrease after PDT with verteporfin was an uncommon event; the risk did not outweigh the benefits of therapy previously reported. When considering verteporfin therapy, patients should be warned of the possibility of this serious adverse event.

Acute Disease↗

PubMed2004

Visual acuity through fresnel, refractive, and hybrid diffractive/refractive prisms.

BACKGROUND: This article compares the effect on visual acuity of the Fresnel and wedge-shaped refractive prisms with newly developed hybrid diffractive/refractive prisms (ComPrisms), which combine a wedge-shaped refractive prism with a diffractive component. The diffractive component of hybrid elements can be designed to correct the chromatic aberration of the refractive component. METHODS: The monocular visual acuity of 21 subjects and binocular acuity of 20 subjects were measured with computer-generated logMAR charts. Visual acuity was measured without prisms (NP) and through ComPrisms, 3M Press-on Fresnel, and acrylic refractive prisms of 20delta, 30delta, and 40delta powers. RESULTS: A repeated measures analysis of variance indicates a significant main effect of treatment (without prisms and through the three types of prisms) at each prism power, both monocularly and binocularly. Results of the Scheffé test for all possible comparisons between pairs of means of the treatments are provided. CONCLUSIONS: Although all the prisms reduced visual acuity, the ComPrisms provide significantly better visual acuity than acrylic refractive or 3M Press-on Fresnel prisms of equivalent power

Adult↗

PubMed1996

Visual acuity and accommodation in infants and young children with Down's syndrome.

Accommodation and visual acuity were measured in 53 children with Down's syndrome aged between 12 weeks and 57 months. Results were compared with data for 136 control (typically developing) children aged between 4 weeks and 48 months. Whereas the control children accommodated accurately on near targets, accommodation was defective in 92% of the children with Down's syndrome, and there was no change in accommodative ability with age. On the other hand, visual acuity lay within normal limits for the younger children. Children over the age of 2 years showed a below-normal visual acuity, which is not explained either by refractive error or by the effect of poor accommodation. The data suggest a sudden change in the rate of development of visual acuity which may be associated with physiological changes in the visual cortex. Previously reported defects of accommodation and visual acuity in older children and adults with Down's syndrome are confirmed by our findings in infants and young children.

Accommodation, Ocular↗

PubMedDate not supplied

Combining refractive error and uncorrected visual acuity to assess the effectiveness of refractive corneal surgery.

Residual refractive error and uncorrected visual acuity are two frequently measures used to assess the effectiveness of refractive corneal surgery. Nordan and colleagues have suggested a Visual Function Index which combines these two measures in one quantitative measure. This article presents a Visual Function Score for radial keratotomy which includes a set of qualitative categories (excellent, good, fair, poor) and specifies the clinical values for refractive error and visual acuity in each category. There was substantial agreement among ophthalmologists who reviewed the category definitions, and we think that the Visual Function Score improves our ability to objectively assess surgical outcome. Application of the score to the Prospective Evaluation of Radial Keratotomy (PERK) Study data yielded closer agreement with refractive error results than with visual acuity values. The Visual Function Score lowered the classification of eyes that were hyperopic but had sufficient accommodation to overcome so that a high visual acuity result could be achieved. The inclusion of astigmatism values would be an important next step in the development of composite measures for the assessment of refractive surgery. In the future, a multifactorial index or score may be used to estimate the outcome of reported surgical procedures.

Adult↗

PubMed2003

Validation of novel and objective measures of microsurgical skill: Hand-motion analysis and stereoscopic visual acuity.

Our purposes were: 1) to establish the predictive validity of stereoscopic visual acuity and microsurgical performance, and 2) to establish the construct and concurrent validity of hand-motion analysis as an objective and sensitive measure of microsurgical performance. Using a surgical microscope, 50 surgical residents completed a standardized microsurgical suturing task at baseline and following microsurgical training. Microsurgical performance was evaluated by blinded, expert microsurgeons using global rating scales. Measures of stereoscopic visual acuity and hand-motion analysis were correlated with expert global rating scores. Global rating scores correlated significantly with number of hand movements (r = -0.47, P = 0.001) and hand-travel distance (r = -0.37, P = 0.008). Economy of hand-motion improved significantly following microsurgical training (number of hand movements, P = 0.046; hand-travel distance, P = 0.04). Measures of stereoscopic visual acuity did not correlate significantly with global rating scores. Hand-motion analysis appears to be an objective and sensitive instrument for assessing microsurgical performance, with evidence of both concurrent and construct validity. The predictive validity of stereoscopic visual acuity and microsurgical performance remains unclear.

Adult↗

PubMed1998

Long-term effect of hypermetropic anisometropia on the visual acuity of treated amblyopic eyes.

AIM: To evaluate the effect of the extent of hypermetropic anisometropia on the long term visual acuity results in amblyopic eyes following their treatment by occlusion. METHODS: The visual acuity of 86 patients, who had been treated for unilateral amblyopia by occlusion of the fellow eye and followed up at least to the age of 9 years, was examined 6.4 years, on average, after cessation of treatment. Patients were divided into two groups--those with a small amount of hypermetropic anisometropia, where the spherical equivalent difference between the eyes ranged between 0 and +1.50 dioptres, and those with a large amount of hypermetropic anisometropia, where the difference was +1.75 dioptres or greater. RESULTS: Deterioration of visual acuity after cessation of occlusion treatment occurred in 51% of the patients in the group with a small amount of anisometropia and in 75% of the patients in the group with a large amount. At cessation of treatment, the average visual acuity in both groups was 20/40+. At the long term follow up examination, however, the average visual acuity was 20/40- and 20/70, respectively. This difference was statistically significant. CONCLUSIONS: Hypermetropic anisometropia greater than 1.50 dioptres appears to be a risk factor for deterioration of visual acuity in the long term, following treatment of amblyopic eyes by occlusion of the fellow eye.

Adolescent↗

PubMed1991

The effect of retrobulbar anesthesia on visual acuity in planned extracapsular cataract extraction.

To our knowledge, this is the first evaluation of the effect of retrobulbar anesthesia on visual acuity. We compared the preoperative best corrected near visual acuity of 30 consecutive patients undergoing planned extracapsular cataract extraction with their best corrected near visual acuity 10 minutes following successful retrobulbar anesthesia. The mean decrease in acuity was 2.83 lines on a Jaeger near card. Postinjection visual acuity did not change in four eyes. In general, the longer the globe axial length, the greater the decrease in visual acuity following retrobulbar block. There was no significant correlation between postinjection acuity and patient age or volume of anesthetic injected.

Aged↗

PubMed1999

A 25-year prospective study of visual acuity in the Japan Air Self Defense Force personnel.

BACKGROUND: In the Japan Air Self Defense Force (JASDF), new vision standards for student pilots allow lower uncorrected monocular acuity (from 1.0 to 0.8). In flight environments, where the use of corrective lenses may present problems, the risk of decreasing visual acuity in pilots who should wear corrective lenses must be defined. METHODS: We conducted a 25-yr prospective study of visual acuity with regard to distance vision in 752 JASDF nonaviation personnel followed from ages 20 to 45. The test subjects were divided into four groups according to their right monocular visual acuity at entry: > or =1.0, between 0.9 and 0.7, between 0.6 and 0.2, and <0.2. RESULTS: At entry, 94.1% of all subjects had visual acuity > or =0.7. The proportion of subjects who required corrective lenses for distance increased with age from 15.8% to 37.1%. After 25-yr, 30.2% of subjects with visual acuity > or =1.0 at entry and 62.7% of subjects with visual acuity between 0.9 and 0.7 at entry required corrective lenses. CONCLUSIONS: Over 25 yr, the population with the best eyesight at age 20 had a lower increase in the need for corrective lenses than the population with visual acuity between 0.9 and 0.7 at age 20. These results suggest an increased risk of visual acuity loss in pilots over time as a result of the lower vision standards for student pilots in the JASDF.

Adult↗

PubMed2005

Effect of artificial tears on visual acuity.

PURPOSE: To study the effect of commonly used preservative free artificial tear, carboxymethylcellulose (CMC) 0.5% (Refresh Plus, Allergan, Irvine, California) on visual acuity in symptomatic dry eye (SDE) and asymptomatic dry eye (ADE) patients. DESIGN: Nonrandomized prospective clinical trial. METHODS: Prospective study involving 20 patients (40 eyes) with SDE and 20 patients (40 eyes) with ADE, all 40 years and older, were recruited from a clinic setting over a 1-month period. Distance visual acuity was measured by the Early Treatment of Diabetic Retinopathy Study (ETDRS) vision chart and near visual acuity was measured by the Lighthouse Near Vision chart before and 30 seconds after instillation of one drop of CMC. Distance and near visual acuity was measured both with and without correction. The duration of action of CMC was measured at 1-minute intervals until the patient's visual acuity returned to pretear level. RESULTS: In both SDE and ADE groups, uncorrected and corrected near and distance vision showed a statistically significant improvement after the use of CMC (P < .05). There was no statistically significant difference in improvement between the SDE and ADE groups in all categories (P values > .05). The mean duration of improvement of vision was 2.93 minutes in the SDE group and 3.70 minutes in the ADE group (P = .036). CONCLUSIONS: CMC 0.5% provides a temporary yet significant improvement in the visual acuity of SDE and ADE patients. The effect of artificial tears on visual acuity may be of diagnostic value in detecting ocular surface abnormality in symptomatic and asymptomatic patients.

Aged↗

PubMed2005

Incremental exercise in dynamic visual acuity.

As research is limited the purpose of this study was to investigate dynamic visual acuity while cycling at different exercise loads. Accuracy of dynamic visual acuity scores of 20 college-age participants was analyzed by a repeated-measures analysis of variance which indicated improved dynamic visual acuity during cycling as the intensity of exercise increased. A retention test conducted two days after testing yielded evidence of trainability of dynamic visual acuity. In the discussion findings were compared to other visual functions associated with exercise.

Adolescent↗

PubMed1995

Spherocylindrical refractive errors and visual acuity.

BACKGROUND: Understanding the relation between refractive error and visual acuity is complicated if astigmatic blur is present. No models are in widespread use that allow the combination of spherical and astigmatic errors for the purpose of predicting visual performance. METHODS: Models for combining spherical and astigmatic errors are discussed, and predictions of these models using data from the literature are presented. RESULTS: Three models for combining astigmatic with spherical errors are shown to predict visual acuity performance in uncorrected myopic refractive errors. A dioptric vector addition model is shown to have advantages over other candidate models. CONCLUSIONS: It is possible to combine spherocylindrical refractive errors into a single value when the objective is to correlate these values with visual acuity performance.

Eyeglasses↗

PubMed2003

Visual acuity after penetrating keratoplasty for pseudophakic and aphakic bullous keratopathy.

PURPOSE: To identify prognostic factors that determine the visual acuity after penetrating keratoplasty (PKP) for bullous keratopathy secondary to cataract surgery. SETTING: Department of Ophthalmology, University Hospital Antwerp, Antwerp, Belgium. METHODS: Twenty-six patients who had PKP for bullous keratopathy were examined before and after surgery. The patients were divided into 3 groups: pseudophakic bullous keratopathy (PBK) after cataract extraction with implantation of a posterior chamber intraocular lens (PC IOL) (Group 1) or an anterior chamber IOL (AC IOL) (Group 2); aphakic bullous keratopathy (ABK) (Group 3). The following parameters were recorded: preoperative and postoperative visual acuity, age at the time of surgery, interval between cataract surgery and development of bullous keratopathy, presence of an AC IOL or a PC IOL, aphakia, and presence of concomitant ocular pathology. RESULTS: Visual acuity improved in Group 1 (0.02 to 0.26); no visual improvement was observed in the other groups. Posterior segment damage occurred in one third of the patients in Group 1 and in all patients in the other groups. Patients with an intact posterior segment had a significantly better visual outcome. In eyes without posterior segment pathology, visual acuity improved from a mean of 0.03 (range 0 to 0.20) to a mean of 0.37 (range 0.03 to 0.90). In eyes with posterior segment pathology, no visual acuity improvement could be obtained. CONCLUSIONS: The most important negative prognostic factors affecting visual acuity were the presence of concomitant ocular pathology, an AC IOL, and a long interval between surgery and the development of bullous keratopathy.

Aged↗

PubMedDate not supplied

Cone-rod dysfunction in patients with unexplained reduction in visual acuity.

Electrophysiologic tests were performed in 233 patients who complained of reduced visual acuity with no satisfactory clinical explanation. The functional integrity of the retina was assessed from the light- and dark-adapted electroretinogram. Macular function and conduction in the optic nerves were estimated from the flash visual evoked potentials. Of the 233 patients 78 were grouped together on the basis of the electrophysiologic and clinical findings. They were characterized by subnormal electroretinogram responses with the cone system more affected than the rod system. The flash visual evoked potential responses were of abnormal waveform and prolonged implicit times. Most of these patients exhibited normal fundi. The reduction in visual acuity, the degree of electroretinogram deficits and the pattern of the visual evoked potential responses were similar in both eyes of each patient, indicating a symmetric disorder. Slight deterioration of visual acuity and electrophysiologic variables were observed in 37 of the patients who were followed up over a period of up to 8 years. The electrophysiologic findings indicate that about 20% of patients complaining of unexplained reduction in visual acuity were suffering from a diffuse retinal disorder affecting the peripheral retina as well as the macular region. On the basis of electrophysiologic findings and clinical symptoms, we suggest grouping these patients under a new entity: cone-rod dysfunction.

Adaptation, Ocular↗

PubMed1988

Validity and reliability of visual acuity measurements.

A more scientific method than the Snellen chart for determining visual acuity is imperative for research studies and is desirable in many clinical situations. The psychometric method using the constant contour interaction S-chart of Flom has been regarded as an accurate and reliable visual acuity measure and has been used widely for research purposes. This paper compares visual acuity measured by the S-chart with that measured by the Snellen and Bailey--Lovie charts. The results indicate that the Bailey--Lovie chart is a valid, reliable and rapid method of measuring threshold visual acuity for research purposes.

Adolescent↗

PubMed1989

[Visually evoked potentials and visual acuity of the young child].

Interest in the development of visual acuity in young infants is increasing. At this age a reliable estimation of visual function is hazardous. This paper highlights the role of flash- and pattern evoked visual potentials. Flash evoked potentials are valuable in following development and/or recovery of visual acuity intra-individually as well as in providing an estimation of sensitiveness to light. Pattern evoked potentials may give an estimation of maturation of the visual system: these potentials also give an objective measurement of visual acuity.

Child, Preschool↗

PubMed2003

A computerized method of visual acuity testing: adaptation of the early treatment of diabetic retinopathy study testing protocol.

PURPOSE: To develop a computerized method of visual acuity testing for clinical research as an alternative to the standard Early Treatment for Diabetic Retinopathy Study (ETDRS) testing protocol, and to evaluate its test-retest reliability and concordance with standard ETDRS testing. DESIGN: Test-retest reliability study. METHODS: Multicenter setting of a study population of 265 patients at three clinical sites. Visual acuity was measured with both the electronic visual acuity testing algorithm (E-ETDRS) and standard ETDRS protocol (S-ETDRS) twice on one eye of each patient. E-ETDRS testing was conducted using the electronic visual acuity tester (EVA), which utilizes a programmed Palm (Palm, Inc, Santa Clara, California, USA) hand-held device communicating with a personal computer and 17-inch monitor at a test distance of 3 meters. RESULTS: For the E-ETDRS protocol, test-retest reliability was high (r = 0.99; with 89% and 98% of retests within 0.1 logMAR and 0.2 logMAR of initial tests, respectively) and comparable with that of S-ETDRS testing (r = 0.99; with 87% and 98% of retests within 0.1 logMAR and 0.2 logMAR of initial test, respectively). The E-ETDRS and S-ETDRS scores were highly correlated (r = 0.96 for initial tests and r = 0.97 for repeat tests). Based on estimates of 95% confidence intervals, a change in visual acuity of 0.2 logMAR (10 letters) from a baseline level is unlikely to be related to measurement variability using either the E-ETDRS or the S-ETDRS visual acuity testing protocol. CONCLUSIONS: The E-ETDRS protocol has high test-retest reliability and good concordance with S-ETDRS testing. The computerized method has advantages over the S-ETDRS testing in electronically capturing the data for each tested letter, requiring only a single distance for testing from 20/12 to 20/800, potentially reducing testing time, and potentially decreasing technician-related bias.

Adolescent↗

PubMed2004

Maternal fish oil supplementation in lactation: effect on visual acuity and n-3 fatty acid content of infant erythrocytes.

Studies on formula-fed infants indicate a beneficial effect of dietary DHA on visual acuity. Cross-sectional studies have shown an association between breast-milk DHA levels and visual acuity in breast-fed infants. The objective in this study was to evaluate the biochemical and functional effects of fish oil (FO) supplements in lactating mothers. In this double-blinded randomized trial, Danish mothers with habitual fish intake below the 50th percentile of the Danish National Birth Cohort were randomized to microencapsulated FO [1.3 g/d long-chain n-3 FA (n-3 LCPUFA)] or olive oil (OO). The intervention started within a week after delivery and lasted 4 mon. Mothers with habitual high fish intake and their infants were included as a reference group. Ninety-seven infants completed the trial (44 OO-group, 53 FO-group) and 47 reference infants were followed up. The primary outcome measures were: DHA content of milk samples (0, 2, and 4 mon postnatal) and of infant red blood cell (RBC) membranes (4 mon postnatal), and infant visual acuity (measured by swept visual evoked potential at 2 and 4 mon of age). FO supplementation gave rise to a threefold increase in the DHA content of the 4-mon milk samples (P < 0.001). DHA in infant RBC reflected milk contents (r = 0.564, P < 0.001) and was increased by almost 50% (P < 0.001). Infant visual acuity was not significantly different in the randomized groups but was positively associated at 4 mon with infant RBC-DHA (P = 0.004, multiple regression). We concluded that maternal FO supplementation during lactation did not enhance visual acuity of the infants who completed the intervention. However, the results showed that infants with higher RBC levels of n-3 LCPUFA had a better visual acuity at 4 mon of age, suggesting that n-3 LCPUFA may influence visual maturation.

Adult↗