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Results for “Visual Acuity”

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At least 307 records · Page 17Linked to original sources

PubMed1992

[Temporal integration in diseased eyes. III. Fixation movements in visual acuity testing].

The fixation movements which occur during visual acuity testing were observed in order to clarify the mechanism behind the critical duration in visual acuity testing, which we found in a previous study to be significantly longer in central serous retinopathy and macular edema. Photoelectric oculography (p-EOG) was used to record horizontal eye movement in this study. In normal eyes the frequency and amplitude of the microsaccades were smaller while the acuity target was shown than when it was not shown. This phenomenon was also observed in eyes with macular edema. These results suggest that microsaccades play no positive role in the reading of visual acuity targets, and that they bear little relation to the phenomenon of critical duration in visual acuity testing.

Adult↗

PubMed1987

Visual acuity, corrective lenses, and accidents in helicopter pilots.

The visual acuity of 38 helicopter pilots experiencing serious air accidents was compared to that of a control group of 72 pilots, matched for age, aircraft, and hours of flight. Decrease in visual acuity was divided into two groups: 1) minor decreases in vision up to 20/25 (not requiring corrective lenses); and 2) visual acuity of 20/30 or less with correction to 20/20. Minor decreases in visual acuity were found in 23.7% (9/38) of those in the accident group compared to 25.0% (18/72) in the control group. There were more pilots in the control group who needed corrective lenses (12.5% (18/72) versus 2.8% (1/38), p less than 0.07). We conclude that helicopter pilots with corrective lenses or minor uncorrected decreases in visual acuity are not at increased risk for serious air accidents.

Accidents, Aviation↗

PubMed1995

Grating visual acuity in eyes with retinal residua of retinopathy of prematurity. The Cryotherapy for Retinopathy of Prematurity Cooperative Group.

OBJECTIVES: To compare grating visual acuity of eyes with varying severity of retinal residua of retinopathy of prematurity to grating visual acuity of eyes that did not have acute-phase retinopathy of prematurity, showed no ocular abnormalities on follow-up, and were from patients who passed neurodevelopmental screening questions. DESIGN: Monocular grating visual acuity was measured by means of the Teller acuity card procedure when children reached 1, 2, 3 1/2, and 4 1/2 years of age. PATIENTS: A total of 1398 children with birth weights less than 1251 g whose acute-phase retinopathy of prematurity was documented as part of the Multicenter Cryotherapy for Retinopathy of Prematurity Study and who participated in follow-up visual acuity testing. RESULTS: Eyes with no or mild residua of retinopathy of prematurity showed a mean visual acuity similar to that of the comparison group. Eyes in a subgroup with abnormally straightened temporal retinal vessels showed a mean visual acuity approximately 1 octave below that of the comparison group. Mean visual acuity scores from eyes with macular heterotopia ranged from 1 octave (at 1 year) to more than 2 octaves (at 4 1/2 years) below the mean visual acuity of the comparison group. Mean visual acuity scores for the few eyes in the retinal fold or partial detachment group that had quantifiable visual acuity were well below the means for the comparison group. CONCLUSIONS: Acute-phase retinopathy of prematurity that regresses without retinal residua produces no deficit in grating visual acuity between 1 and 4 1/2 years of age. In contrast, eyes with macular heterotopia show a visual acuity deficit, and the deficit is greater at older than at younger ages. Eyes with retinal fold or partial detachment that have measurable visual acuity show large visual acuity deficits at all ages.

Acute Disease↗

PubMed1991

The relationship of visual acuity, refractive error, and pupil size after radial keratotomy.

To better define the relationship between residual refractive error, uncorrected visual acuity, and pupil diameter, we compared 42 eyes that had an eight-incision radial keratotomy according to the Prospective Evaluation of Radial Keratotomy Study protocol with 42 matched control eyes. The parameters measured were best corrected visual acuity, uncorrected visual acuity, and the change in cycloplegic refraction with enlarging pupil diameter. The best corrected visual acuity was 20/16 in both the radial keratotomy and control groups, but the variability (SD) was higher in the radial keratotomy group. The average uncorrected visual acuity was 0.35 (35%) better in the radial keratotomy group, but the variability was 1.77 times higher. Change in refraction with dilation occurred in 9% of the controls and 36% of the radial keratotomy patients, indicating a significant difference (P = .002). The change in refraction with dilation in the eyes with radial keratotomy was almost equally split between a hyperopic change (17%) and a myopic change (18%), which was much different than in the control eyes, only 2% of which changed in a hyperopic direction and 7% in a myopic direction. The radial keratotomy patients with a myopic change had the best uncorrected visual acuity, indicating that positive spherical aberration yielded the best aspherical surface for uncorrected visual acuity.

Adult↗

PubMedDate not supplied

Pattern visual evoked cortical potentials predict postoperative visual acuity after cataract surgery in patients with glaucoma.

Visual acuity after cataract surgery in patients with glaucoma cannot be predicted accurately. We studied preoperative recordings of pattern visual evoked cortical potentials (PVECPs) to evaluate postoperative vision in patients with glaucoma and cataract. Fifty patients with glaucoma and no cataract and 31 patients with glaucoma and cataract who underwent phacoemulsification were included in this study. Age and P100 component significantly correlated with postoperative visual acuity with multiple linear regression analysis. A significantly greater number of patients with glaucoma, cataract, and a P100 component preoperatively showed a visual acuity of 0.7 or better postoperatively, as compared to those without a P100 component. PVECP before cataract surgery was able to predict postoperative good visual acuity in patients with glaucoma and cataract.

Adolescent↗

PubMed1986

Prognostic value of laser interferometric visual acuity in amblyopia therapy.

There has been no simple clinical test which accurately predicts post-therapy visual acuity in amblyopic eyes. Since grating test patterns generally yield optimal visual acuity in amblyopic eyes, the authors sought to determine if pre-therapy laser interferometric grating visual acuity would predict conventional post-therapy visual acuity in functional amblyopia. In 90% of the patients who completed therapy, the pre-therapy laser visual acuity was within two lines of the post-therapy Snellen visual acuity. Thus, pre-therapy laser visual acuity is a good prognostic indicator of conventional post-therapy visual acuity in amblyopic eyes.

Adolescent↗

PubMed1996

Visual acuity disturbance in subjects over 50 years of age in a population-based cataract survey.

Visual acuity is still an essential examination item in cataract epidemiological studies, even though this parameter lacks objective reliability. A population-based epidemiological study was conducted in a rural area of Japan to find out the relationship between visual acuity levels and cataracts, the types of gradings of which were evaluated by an objectively reliable method through lens images, and to serve as a sample for researchers who perform epidemiological studies on cataract but lack the latest methodology. 863 participants above 50 years of age were examined and those previously diagnosed with ocular diseases which affect visual acuity were excluded from the analysis as much as possible. The mean visual acuity (LogMAR) in subjects in their 50s, 60s, 70s and over 80 years of age was 1.1, 1.0, 0.7 and 0.4, respectively. Both the mean and the distribution of visual acuity showed a statistically significant relationship to ageing (p < 0.01, p < 0.01). Both age and cataract grading showed a statistically significant relationship to visual acuity (p < 0.01), but there was no significant interaction effect between these two variables upon visual acuity. Visual acuity worsened remarkably with ageing in the eyes with grade III, whereas that of eyes with grades I and II remained fairly stable at a level of 0.7-1.0, except for those above 80 years of age. A fairly good visual acuity of 1.0, 0.8 and 0.7 remained in the eyes with pure cortical cataract of grades I, II and III, respectively, whereas those with mixed type cataract were 0.9, 0.6 and 0.3, respectively.

Aged↗

PubMed2006

Impact of macular edema on visual acuity in uveitis.

OBJECTIVE: To investigate the impact of cystoid macular edema (CME) on visual acuity in patients with uveitis. DESIGN: Cross-sectional study. PARTICIPANTS: The data from 529 patients (842 eyes) with uveitis were analyzed. MAIN OUTCOME MEASURES: We recorded gender and age of the patients, anatomic site and diagnosis of uveitis, associations with systemic diseases, onset and duration of uveitis, presence of CME, best-corrected visual acuity, and the causes of decrease in visual acuity. RESULTS: Cystoid macular edema was noted in 175 (33%) of all uveitis patients, of whom 77 (44%) had visual acuity of 20/60 or less in at least 1 eye. The mean visual acuity for eyes with CME was significantly worse than for eyes without CME (0.25 vs. 0.4; P = 0.003). Of all uveitis patients, 185 (35%) had visual acuity of 20/60 or less in at least 1 eye, which was caused by CME in 77 (42%) patients. Poor visual acuity in patients with CME was associated with the advanced age of the patients, chronic inflammation, and various specific uveitis entities. The development of visually impaired or blind eyes in patients with panuveitis and intermediate uveitis was caused in most cases by CME (59% and 85%, respectively). CONCLUSIONS: Cystoid macular edema was a major cause of visual loss in patients with uveitis. The unsatisfactory visual acuity in patients with uveitis underlines the need for improved management of this complication.

Adolescent↗

PubMed2000

Decreased visual acuity in patients with cytomegalovirus retinitis and AIDS.

PURPOSE: To investigate the causes of decreased visual acuity in patients with cytomegalovirus (CMV) retinitis in the acquired immunodeficiency syndrome (AIDS). METHODS: All human immunodeficiency virus (HIV)-positive patients seen in two ophthalmology units over a 15 month period from September 1996 were included in this retrospective study. A detailed ophthalmic examination was performed on all patients and in addition those with CMV retinitis underwent serial fundus photography. Decreased visual acuity was defined as a best corrected visual acuity < or = 6/12. CMV and retroviral treatment, CD4+ count and HIV viral load were also documented for each patient. RESULTS: Of 110 patients seen over the 15 month period, 26 (41 eyes) had a diagnosis of CMV retinitis. Twelve patients (16 eyes) with CMV retinitis had decreased visual acuity. The decreased visual acuity in 7 eyes was initially due to the CMV retinitis involving the macula and the optic nerve. Retinal detachment was responsible in 2 eyes and optic nerve atrophy in 1 eye. In 6 eyes (4 patients) the decreased visual acuity was due to a maculopathy--cystoid macular oedema and/or an epiretinal membrane in the presence of an inactive zone 2 or 3 CMV retinitis--with all these patients exhibiting a vitritis of varying grade. The decreased visual acuity in the maculopathy subgroup was irreversible in all except 1 eye, and 2 eyes in this category later developed a cataract. CONCLUSION: In this series, CMV-retinitis-'related' maculopathy was a major (38%) cause of decreased visual acuity, occurring in the absence of zone 1 retinitis and despite inactive peripheral CMV retinitis. A varying degree of vitritis was an associated feature in all these patients. This study therefore highlights maculopathy as an important and previously unrecognised significant cause of visual morbidity in CMV retinitis.

AIDS-Related Opportunistic Infections↗

PubMed2005

Effect of water turbidity on the visual acuity of harbor seals (Phoca vitulina).

The underwater visual acuity (the angle subtended by the minimal resolvable line width of high contrast square wave gratings at a viewing distance of 2m) of two male harbor seals was determined at different levels of water turbidity. Starting with visual acuity angles of 5.5' and 12.7' in clear water we found visual acuity to decrease rapidly with increasing turbidity at rates of 7.4' and 6.0' per formazin nephelometric unit (FNU). Besides the individual differences in visual performance of the harbor seals tested, our results reveal a dramatic loss of visual acuity even at moderate levels of turbidity. At sites in the German Wadden Sea, where harbor seals are known to roam and forage, we measured turbidity levels exceeding 40FNU. These data suggest that turbidity has to be considered as an important factor in the sensory ecology of pinnipeds.

Animals↗

PubMed1996

[Early correction of hyperopia and astigmatism in children leads to better development of visual acuity].

BACKGROUND: From the investigations of Wiesel and Hubel an influence of early spectacle correction of refractive errors on visual development is to be expected. Nevertheless the benefit of early spectacle correction in young children is being discussed controversially. PATIENTS AND METHODS: In a retrospective study the records of 103 strabismic children were analyzed. Myopic children and those with hypermetropia less than 2.0 diopters without astigmatism were excluded from this study. Visual acuity of the dominant eye only was compared between the following subgroups: early spectacle correction (A) not later than at the age of 30 months; "early" spectacle correction (B) between 30 months and 4 years; late spectacle correction (S) after the age of 8 years. In further subgroups we analyzed hypermetropia of more than 3.0 diopters and the combination of hypermetropia and astigmatism of 1.0 diopter or more. Visual acuity was determined using commercially available target projectors 2 times with an interval of at least 3 months. For analysis, the mean of these two examinations was calculated. In all children visual acuity after the age of 8 years was analyzed, the children of group S wore their glasses at least 6 months before the first determination of visual acuity included in this study. The dominant eye was analyzed only. RESULTS: Early corrected eyes developed better visual acuity than late corrected ones: 45% of the early corrected children (A + B) had a visual acuity exceeding 1.0 (20/20) versus 22% in the late corrected (S) subgroup (p = 0.046). 53% of the children corrected within the first 30 months (A) developed a visual acuity exceeding 1.0 (20/20) compared with 22% in the late corrected subgroup (p = 0.019). In hypermetropia exceeding 3.0 diopters (without astigmatism) the difference of early correction (A + B) compared with late correction (S) was even more significant: 72% of early corrected children developed a visual acuity of better than 1.0 (20/20), but no child corrected late did so (p = 0.0015). On the other hand, no child in these 2 subgroups developed a visual acuity of below 1.0 (20/20). Astigmatic eyes had a worse visual acuity: 13% of the early corrected subgroup (A) developed a visual acuity below 1.0 (20/20) versus 55% in the late corrected (S) subgroup (p = 0.024). CONCLUSION: Early correction of hypermetropia (3.0 diopters or more) and of hypermetropic astigmatism (1.0 diopter or more) results in better development of visual acuity as measured at the age of 8 years or later. Since visual acuity of better than 1.0 (20/20) is "normal", late corrected children often did not develop "normal", visual acuity. By early correction of relevant hypermetropia and hypermetropic astigmatism this "refractive amblyopia" at least in part could be avoided.

Astigmatism↗

PubMed1997

Visual acuity and macular hole size after unsuccessful macular hole closure.

PURPOSE: To evaluate the visual acuity, change in macular hole size, and change in subretinal fluid cuff size after unsuccessful macular hole closure. METHODS: Forty-two consecutive eyes with macular hole and unsuccessful surgery for macular hole were studied. Preoperative and postoperative best-corrected visual acuities were tested according to the Early Treatment Diabetic Retinopathy Study (ETDRS) protocol, and changes were compared. Preoperative and postoperative fundus photographs were analyzed on a photograph documenter for changes in diameter of the macular hole and surrounding subretinal fluid cuff. RESULTS: Mean visual acuity decreased from 20/133 preoperatively to 20/154 postoperatively (mean loss, 0.79 ETDRS line). Mean diameter of the macular hole enlarged 22%; mean diameter of the visible surrounding subretinal fluid cuff enlarged 36%. A decrease in best-corrected visual acuity postoperatively was correlated with better preoperative visual acuity, earlier macular hole stage, and shorter duration. Enlargement in the diameter of the macular hole and fluid cuff did not correlate with better preoperative best-corrected visual acuity, earlier macular hole stage, or shorter duration. In 23 eyes that had failed previous surgery, macular hole surgery was anatomically successful in 17 (65%) (mean improvement, 3.7 ETDRS lines; mean best-corrected final visual acuity, 20/74). CONCLUSION: After macular hole surgery, anatomically unsuccessful closure of the hole correlates with small enlargements in the diameter of the macular hole and its surrounding subretinal fluid cuff, and with a slight decrease in visual acuity. Macular hole closure after repeat surgery improves visual acuity outcome in the majority of retreated eyes.

Aged↗

PubMed1995

Reliability of visual acuity measurements and screening under field conditions.

PURPOSE: The purpose of this analysis was to investigate the reliability of visual acuity screening and measurements made under field conditions when standardization of all test conditions is not possible. SETTING AND METHODS: In the Washington County Follow-Up Eye Study conducted in 1985 among cases of ocular histoplasmosis and controls from the same community who had been selected in 1970, a primary goal was to obtain a current visual acuity measurement of each eye of each participant in order to assess 15-year changes in visual acuity. Both visual acuity screening and measurement were accomplished on two separate occasions and in two separate locations (home or workplace and clinic) for 308 eyes and 317 eyes, respectively, of 161 participants. Screening was used to classify the visual acuity as 20/40 or better, worse than 20/40 but at least 20/160, or worse than 20/160. Screening and measurement were accomplished on at least one occasion for the eyes of 192 of 216 eligible individuals. RESULTS: Among 308 eyes screened twice, 289 (94%) were classified identically (kappa = 0.80). Among 317 eyes with visual acuity measured on two occasions, the measurements were within two lines for 305 eyes (96%; kappa = 0.50). Among eyes for which classifications of visual acuity from screening and measurement could be compared, 325 (96%) of 340 assessed at home and 326 (96%) of 338 assessed in clinic were classified in the same way (kappa = 0.86 and 0.88, respectively). CONCLUSION: Despite the unavoidable lack of standardization of test conditions when visual acuity was screened and measured in the home or work-place, the results were highly reliable when compared with visual acuity testing in the clinic under standard conditions.

Aged↗

PubMed2002

Impaired functional visual acuity of dry eye patients.

PURPOSE: To report dry eye patients' functional visual acuity, which was measured after sustained eye opening for 10-20 seconds, as a simulation of visual function of daily acts of gazing, which is defined as looking at an object with involuntary blink suppression. METHODS: Interventional clinical nonrandomized comparative trial. We measured ordinary best-corrected visual acuity and functional visual acuity in non-Sjögren's syndrome (non-SS, N = 10) and Sjögren's syndrome (SS, N = 12) patients and in normal controls (N = 8), prospectively. Surface regularity index (SRI) of corneal topography was also measured under routine circumstances and after sustained eye opening. Blink rates while gazing were measured during reading in another 28 dry eye patients and during driving in another 8 normal controls. RESULTS: Functional visual acuity did not change (1.27-1.16) in normal controls, but decreased significantly from 1.18-0.336 in non-SS patients (P = .0007) and from 1.15-0.228 (P < .00001) in SS patients. SRI after sustained eye opening increased in non-SS (P = .032) and SS patients (P = .0007), but not in the normal controls. Blink rates during reading (P < .001) and driving (P = .012) were significantly decreased from baseline blink rates. CONCLUSIONS: This study shows that the visual function of dry eye patients becomes abnormal with ocular surface irregularity when the eye is kept open for 10-20 seconds. Our data indicate impaired visual function in dry eye patients while gazing. Functional visual acuity may be important in daily activities.

Automobile Driving↗

PubMed2002

The dependency of logMAR visual acuity measurements on chart design and scoring rule.

BACKGROUND: Visual acuity, increasingly measured using a logarithm of the minimum angle of resolution (logMAR) chart, is the "gold standard" by which the outcomes of the vast majority of clinical trials or interventions are judged. To allow comparison of results across studies, it is important that different charts provide equivalent results. METHODS: In a first experiment, we compared corrected visual acuity measurements from four different logMAR charts (Bailey-Lovie, ETDRS, Regan, and Waterloo). In a second experiment we compared unaided visual acuity scored using a psychometric function with the more clinical by-letter scoring. RESULTS: Experiment 1 showed significantly better visual acuity using the Regan chart compared with the other three charts, and further investigation suggested that this could be due to the font type used. Repeatability data from experiment 2 indicated that no extra repeatability was gained when using psychometric methods compared with the far simpler and quicker by-letter scoring. CONCLUSIONS: When comparing findings between studies, the type of chart and the scoring method used may have a significant effect on the results obtained and should therefore be taken into consideration. Also, the additional time and effort demanded for determining a psychometric function for single readings of the Regan visual acuity chart is not rewarded with improved repeatability.

Adult↗

PubMedDate not supplied

Epiretinal membrane removal in eyes with good visual acuities.

PURPOSE: To evaluate the results of vitrectomy for epiretinal membrane in eyes with a preoperative visual acuity of 20/50 or better. METHODS: The visual results and complications of vitrectomy for epiretinal membranes were analyzed in a retrospective, consecutive case series of 40 eyes of 40 patients treated by a single surgeon. RESULTS: The mean preoperative visual acuity was 20/50 + 2 (range 20/30 + 1 to 20/50 -3). The mean visual acuity improved to 20/40 + 2 (P = 0.02) by the final examination at a mean of 2.4 years following surgery. The status of the lens at the final examination was correlated with the visual results of surgery. Twenty-one eyes were phakic preoperatively and 14 of these eyes had cataracts removed by the final examination. The mean preoperative visual acuity in 7 eyes which were still phakic at the final examination was 20/50 and this decreased to 20/50 -2 (P = 0.82). The mean preoperative visual acuity was 20/50 + 2 in 33 eyes which were pseudophakic by the final examination and this improved to 20/32 -2 (P = 0.005). There were no other serious complications such as retinal detachment or infectious endophthalmitis. CONCLUSIONS: Vitrectomy for epiretinal membranes is safe in eyes with relatively good preoperative visual acuities but cataract surgery is necessary in phakic eyes to achieve long-term visual acuity improvement.

Aged↗

PubMed1993

Dark focus of accommodation and uncorrected visual acuity.

We compared the dark focus of accommodation in 33 healthy children, 19 eyes with good uncorrected visual acuity (1.0 or more) vs. 14 with poor uncorrected visual acuity (below 1.0). The two groups were matched for age and cycloplegic refractive error. Cycloplegic refractive error ranged from +0.15 to +1.75 D in the good visual acuity group and from +0.25 to +1.87 D in the poor visual acuity group. The dark focus was defined as the difference between the refractive error in the dark and the refractive error under cycloplegia. Initially, visual acuity was measured subjectively. Next, refractive error in the dark was measured using the Nidek Autorefractometer AR1600 with its optical target light off. Refractive error under cycloplegia was measured 40 min after the instillation of cyclopentolate hydrochloride using the same autorefractometer. There was a significant correlation between the dark focus and the cycloplegic refractive error (r = -0.53, p < 0.01). Despite an equal refractive error under cycloplegia the dark focus was significantly larger in the eyes with good uncorrected visual acuity than in those with poor uncorrected visual acuity (p < 0.01). Tonic accommodation may influence uncorrected visual acuity.

Accommodation, Ocular↗

PubMed1997

Reproducibility of visual acuity measurements in patients with retinitis pigmentosa.

PURPOSE: To establish the normal short-term range of variation in the measurement of visual acuity in patients with retinitis pigmentosa. METHODS: Sixteen patients (31 eyes) with retinitis pigmentosa, whose visual acuity ranged from 20/25 to 20/200, participated in this prospective clinical study. The best-corrected visual acuity in undilated and in dilated conditions was recorded independently by two masked observers on two visits of each patient within a 2-week interval by means of the Early Treatment Diabetic Retinopathy Study charts (The Lighthouse, Long Island City, NY). RESULTS: Using mixed-model analysis, a reasonable upperbound for intervisit (intraobserver) variability of 6.0 letters for the visual acuity of patients with undilated pupils and 6.3 letters for the visual acuity of patients with dilated pupils and the corresponding maximum interobserver variability of visual acuity of 5.7 letters in patients with either undilated or dilated pupils on the Early Treatment Diabetic Retinopathy Study charts were computed. The overall average interobserver and intraobserver variability in visual acuity ranged from 1.3-2.3 letters. CONCLUSIONS: A change in visual acuity of seven letters or more on the standardized Early Treatment Diabetic Retinopathy Study charts may be considered important in patients with retinitis pigmentosa. For these patients with minor lens opacity, visual acuity measurements obtained with undilated and dilated pupils were similar. These findings help to establish guidelines for monitoring the response of visual acuity during any future therapeutic intervention trials or for determining substantial changes in visual acuity over time when the course of visual acuity loss in such patients is monitored.

Adult↗