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At least 109 records · Page 6Linked to original sources
PubMed1997

Visual impairment in Australia: distance visual acuity, near vision, and visual field findings of the Melbourne Visual Impairment Project.

PURPOSE: To describe the age-specific and gender-specific rates of blindness and visual impairment in urban adults aged 40 years and older. METHODS: A population-based sample of residents was recruited. Presenting and best-corrected distance visual acuities were assessed. Functional near vision was measured at each participant's preferred distance. Visual field examination was performed with a Humphrey Field Analyzer (HFA); those unable to perform the field analyzer test attempted a Bjerrum screen or confrontation field. RESULTS: The study population comprised 3,271 residents (83% of eligible) from ages 40 to 98 years; 54% were women. Overall, 56% of the study population wore distance correction; this was significantly lower in men but higher in the older age groups. Age-adjusted rates of blindness were 0.066% in men and 0.170% in women. Vision with current correction improved after refraction by gender and age. Direct age-standardized rates of functional near vision did not vary significantly by gender. Forty-six people had significant visual field loss in their better eye. The proportion of participants with constriction of the visual field to within 20 degrees of fixation was similar for men and women when controlled for age (odds ratio, 0.81; 95% confidence interval, 0.44 to 1.49) but increased significantly with age controlled for gender. Visual field abnormalities were detected in 548 right eyes (17%) and 533 left eyes (16%). CONCLUSIONS: Although overall rates of blindness because of visual acuity loss were relatively low, nearly three times more people had visual impairment because of visual field loss than visual acuity loss. These results highlight the need to target blindness prevention programs to the aging population, with a special emphasis on women.

Adult↗
PubMed1975

Alcohol and marijuana effects on static visual acuity.

Static visual acuity was measured at two contrast levels (12 and 49%) in ten subjects in a double blind experiment involving five drug conditions of alcohol and marijuana (0.5 ml and 1.0 ml/kg body weight of 95% ethanol, 8 and 15 mg delta-9-tetrahydrocannabinol (THC), and a placebo). We found no statistically significant change in static visual acuity for any of the dose levels at any of the measurement time up to six hours following drug ingestion; this is sharply contrasted with the marked decrements in acuity which were found in the same subjects under the same drug conditions when the targets were in motion and required corrdinated eye movements for their resolution.

Adolescent↗
PubMed2005

Visual acuity and the causes of visual loss in a population-based sample of 6-year-old Australian children.

PURPOSE: To describe the distribution of visual acuity and causes of visual loss in a representative sample of Australian schoolchildren. DESIGN: Population-based cross-sectional study. PARTICIPANTS: One thousand seven hundred thirty-eight predominantly 6-year old children examined during 2003 to 2004. METHODS: Logarithm of the minimum angle of resolution (logMAR) visual acuity was measured in both eyes before and after pinhole correction and with spectacles if worn. Cycloplegic autorefraction (cyclopentolate) and detailed dilated fundus examination were performed. MAIN OUTCOME MEASURES: Visual impairment was defined as any (visual acuity <20/40; <40 letters) or severe (visual acuity < or =20/200; 0-5 letters) for both better and worse eyes. Myopia was defined as spherical equivalent (SE) refraction < or =-0.50 diopters (D), and hyperopia as SE refraction > or =+2.0 D, deemed significant when > or =+3.0 D. Astigmatism was defined as cylinder > or =1.0 D and anisometropia as SE refraction difference between eyes at least 1.0 D. Amblyopia was defined as corrected visual acuity <0.3 logMAR units (<20/40; <40 letters) in the affected eye not attributable to any underlying structural abnormality of the eye or visual pathway, together with a 2-logMAR line difference between the eyes and presence of an amblyogenic risk factor. RESULTS: The mean visual acuity of this sample was 20/25 (49.3 letters). Uncorrected visual impairment was found in the better eye of 23 children (1.3%) and in the worse eye of 71 children (4.1%). The prevalence was higher in girls than boys and among children of lower socioeconomic status. Refractive error was the most frequent cause, accounting for 69.0%, followed by amblyopia (22.5%). Astigmatism was the principle refractive error causing visual impairment and was frequently uncorrected. Presenting visual impairment (using current glasses if worn) was found in the better and worse eyes of 15 children (0.9%) and 54 children (2.8%), respectively. This was mainly due to under corrected or uncorrected refractive error. CONCLUSIONS: This study has documented a relatively low prevalence of visual impairment in a population of Australian children. Uncorrected astigmatism and amblyopia were the most frequent causes.

Child↗
PubMed2002

Accuracy of IRAS GT interferometer and potential acuity meter prediction of visual acuity after phacoemulsification: prospective comparative study.

PURPOSE: To assess and compare the accuracy of 2 methods of predicting visual acuity after phacoemulsification. SETTING: Department of Ophthalmology, Montpellier, France. METHODS: This prospective study evaluated 47 eyes of 47 patients having uneventful phacoemulsification over a 1-month period. All the patients had mild to moderate cataract. Visual acuity recovery was predicted using the white-light IRAS GT interferometer on the 3- and 8-degree wide test area and the Guyton-Minkowski potential acuity meter (PAM). Best corrected visual acuity was evaluated 1 day before and 1 month after surgery. RESULTS: Both the interferometer and PAM underestimated the retinal visual capacity. Three-degree white-light interferometry gave significantly better mean predicted results than 8-degree interferometry and the PAM. There was no statistically significant disparity between predicted and postoperative results with 3-degree interferometry (1.04 +/- 0.57 logMAR; -0.09 +/- 0.27 decimal) (P =.0647) and a statistically significant disparity with 8-degree interferometry (0.89 +/- 0.59 logMAR; -0.13 +/- 0.27 decimal) and the PAM (0.66 +/- 0.62 logMAR; -0.22 +/- 0.24 decimal) (P =.0001). The predicted values were widely dispersed; the correlation indices were 0.38 with the PAM (P =.091), 0.39 with 3-degree interferometry (P =.001), and 0.49 with 8-degree interferometry (P =.0005). CONCLUSIONS: Three-degree white-light interferometry gave more accurate results than 8-degree interferometry and the PAM. The wide dispersion of results and unsatisfactory correlation indices show the tests are poor predictors of individual acuity. They should be used semiquantitatively and the results interpreted in relation to the clinical data. Qualitative methods may be useful in confirming or refuting visual recovery capacity ascertained by quantitative systems.

Adult↗
PubMed1978

Visual acuity and the developing visual system.

The objective measurement of visual acuity in infants is reviewed. Recent techniques have shown that visual acuity levels as early as four to six months after birth. This and other evidence indicates that the most sensitive period in the development of the visual system may be during the first six months of life. With this as a rationale, it is suggested that eye care practitioners consider eye examinations and correction of refractive errors during infancy as a means of prevention of future strabismus and amblyopia.

Child, Preschool↗
PubMed1994

Visual acuity, color vision, and visual search performance at sea.

Visual acuity and color vision were tested during a search and rescue exercise at sea. Fifty-seven watchkeepers searched for orange and yellow life rafts during daylight and for lighted and unlighted life rafts at night with night vision goggles. There were 588 individual watches of one hour each. Measures of wind, waves, and weather were used as covariates. Daytime percentage detection was positively correlated with low-contrast visual acuity and negatively correlated with error scores on Dvorine pseudoisochromatic plates and the Farnsworth color test. Performance was better during the first half-hour of the watch. Efficiency calculations show that color vision selective screening at one standard deviation above the mean would increase daylight search performance by 10% and that one standard deviation visual acuity selection screening would increase performance by 12%. There was no relationship between either acuity or color vision and life raft detection using night vision goggles.

Color Perception↗
PubMed1986

Potential acuity meter for predicting visual acuity after Nd:YAG posterior capsulotomy.

We studied 30 patients with opacifications of the posterior capsule to determine if the potential acuity meter (PAM) could accurately predict final visual outcome after Nd:YAG discussion. The final visual acuity was within one line of the PAM prediction in 22 of 30 patients (73%), better by two or more lines in seven patients (23%), and worse in one patient (4%) by two lines. Although in thicker capsules the final acuity was occasionally better than the PAM prediction, the rates of false negative and false positive predictions were very low. Mild cystoid macular edema (3 patients), age-related macular degeneration (3 patients), intraocular lens status, and level of initial acuity did not diminish PAM accuracy. The PAM effectively predicts final visual acuity after YAG posterior capsulotomy, when used in a patient, unhurried manner.

Adult↗
PubMed1986

Potential acuity meter to predict postoperative visual acuity.

Thirty-three eyes were examined with the potential acuity meter (PAM) to determine preoperatively the expected visual acuity for patients undergoing cataract surgery. The preoperative visual acuity was compared to the best postoperative visual acuity. Although several patients had moderate macular degeneration as well as cataracts, there was an overall accuracy to within two lines of the best visual acuity in 96% of patients. There was a tendency to underestimate rather than overestimate postoperative visual acuity when these readings were in error. The instrument was only used if the cataract examined had some clarity. Older patients who were unsteady had difficulty performing the test.

Cataract Extraction↗
PubMed1979

[The drop of visual acuity with distance and visual fatigue (author's transl)].

Using a new apparatus which enables us to measure in a continual manner the visual acuity for any distance; we have found considerable changes in the acuity between 24 metres and 10 centimetres. A drop in the visual acuity was found at the near vision. From dioptric and non-dioptric factors, we have infered our interpretation, which touches the question of visual fatigue and near vision.

Accommodation, Ocular↗
PubMed1986

Functional vision in patients with neovascular maculopathy and poor visual acuity.

Central visual function is characteristically reported as Snellen acuity at distance and near. We performed functional tests in a group of patients with visual acuity of 20/100 or worse due to macular disease to determine whether there was a relationship between Snellen acuity and functional performance among these patients with poor visual acuity. Our tests of functional performance included currency discrimination, color recognition, reading a clock, and reading large print. Our results suggest that there is a correlation between Snellen acuity and functional vision, even among patients with poor visual acuity. Hence, therapeutic efforts to keep patients' visual acuity at 20/200 rather than 20/400, for example, appears to be justifiable in that better acuity levels seem to be associated with improved functional performance.

Aging↗
PubMed1996

Visual acuity and the causes of visual loss in Australia. The Blue Mountains Eye Study.

BACKGROUND: The Blue Mountains Eye Study is a population-based study of vision and the causes of visual impairment and blindness in a well-defined urban, Australian population 49 years of age and older. METHODS: The logarithm of the minimum angle of resolution (logMAR) visual acuity was measured before and after refraction in 3647 persons, representing an 88% response rate in two postcode areas in the Blue Mountains area, west of Sydney. RESULTS: Refraction improved visual acuity by one or more lines in 45% of participants and by three or more lines in 13%. Visual impairment (visual acuity 20/40 or worse in the better eye) was found in 170 participants (4.7%). Mild visual impairment (Snellen equivalent 20/40 to 20/60 in the better eye) was found in 3.4% moderate visual impairment (20/80 to 20/160 in the better eye) in 0.6%, and severe visual impairment or blindness (20/200 or worse in the better eye) in 0.7%. Visual impairment increased with age from 0.8% of persons 49 to 54 years of age to 42% of persons 85 years of age or older. Visual impairment was significantly more frequent in females at all ages. Among persons with severe visual impairment, 79% were female. After adjusting for age, females were less likely to achieve 20/20 best-corrected visual acuity than males (odds ratio, 0.57; confidence interval, 0.48-0.66). After adjusting for age and sex, no association was found between visual acuity and socioeconomic status. Age-related macular degeneration was the cause of blindness in 21 of the 24 persons with corrected visual acuity of 20/200 or worse. CONCLUSION: Increasing age and female sex were independent predictors of visual impairment.

Adult↗
PubMed1993

The visual acuity for the lateral visual field of the pigeon (Columba livia).

Previous studies on pigeons indicated that the visual acuity for the frontal visual field was much higher than that for the lateral one. Suspecting that the poor values for the lateral field were due to suboptimal testing conditions, we determined the lateral field acuity in eight head-fixed pigeons with high-contrast square-wave gratings. An instrumental conditioning task with water as reinforcer and mandibulation as an operant was used. Subjects achieved a mean acuity value of 12.6 c/deg. The results show that the acuity of the lateral visual field is only slightly lower than that of the frontal field. These data provide a psychophysical basis for ecological observations that pigeons and most other birds gaze laterally when scrutinizing small and distant objects.

Animals↗
PubMed2006

[Value of different measurements of the preoperative visual acuity and perception of Purkinje's vessel shadows for prediction of the postoperative visual acuity after vitrectomy in diabetic vitreous hemorrhage].

BACKGROUND: In cases of strong vitreous hemorrhage due to diabetic vitreo-retinopathy there is an uncertainty for the prediction of postoperative visual acuity after vitrectomy. This study compares the value of different preoperative measurements for the prognosis of postoperative visual acuity. METHOD AND PATIENTS: We evaluated retrospectively the reports of all patients who have been operated by vitrectomy due to diabetic vitreous hemorrhage at our hospital in 2004 (first vitreoretinal surgery). The following measurements were evaluated: preoperative distance and reading VA, last known VA before hemorrhage, laser interference VA, Purkinje's vessel shadow and postoperative distance VA. RESULTS: 42 patients had entire documentation of all evaluated parameters. The preoperative distance VA was 20/1000 (light perception to 20/60), only 3 patients had a reading VA. Laser interference VA was better than red light perception in 13 patients (7 without red light perception). Purkinje's vessel shadows were positive in 22 patients, negative in 17 patients, but 3 patients did not understand the procedure. Prehemorrhage VA was known in 19 patients. Laser interference VA and last known VA prior to hemorrhage (in mean 20 months old) had the best correlation to postoperative VA (p > 0.05). Purkinje's vessel shadow predicts -- if positive -- a postoperative VA of 20/300 or better. CONCLUSIONS: Postoperative VA after vitrectomy due to diabetic vitreous hemorrhage is best predicted by prehemorrhage VA or laser interference VA, especially if no prehemorrhage VA is known. Positive Purkinje's vessel shadow predicts a postoperative VA of 20/300 or better.

Comorbidity↗
PubMed2004

[Color vision and the diagnosis of reduced visual acuity].

Unexplained visual acuity loss requires a systematic approach to gather as many findings of diagnostic value as possible. Most retinal or optic nerve diseases are accompanied by color vision disorders. The type and severity of color vision disorders may provide additional diagnostic or guiding information or may uncover aggravating or simulating factors.

Adult↗
PubMed1979

Micropsia and visual acuity in macular edema. A study of the neuro-retinal basis of visual acuity.

Relative micropsia was measured by a matching technique in patients with unilateral, benign, macular edema. Quantitative assessment of foveolar micropsia to be a sensitive indicator of receptor displacement in this disorder, and may be a useful tool both for diagnosing and for monitoring macular edema. Parallel measurements of grating acuity showed a close proportionality between acuity and micropsia parameters. This result validates a new quantitative theory for the neuro-retinal basis of visual acuity. The theory allows prediction of the proportion of working visual neurons in patients with impaired acuity due to diseases that produce a diffuse loss, or disconnection, of macular cones. Our results indicate that so-called normal visual acuity (1.0 or 20/20) requires no more than 44% of the normal quantity of fovelar, neuro-retinal channels.

Humans↗
PubMed1991

The effect of age and initial visual acuity on the systemic and visual prognosis of central retinal vein occlusion.

Papillophlebitis is the term that is often used to describe a central retinal vein occlusion with preserved visual acuity in a young, healthy patient. Among 194 patients with a diagnosis of central retinal vein occlusion (CRVO), 19 patients were identified who were under 50 years of age and who had visual acuity of 6/12 or better in the affected eye. These patients retained good vision in the affected eye during the course of the disorder with 17 eyes returning to 6/6. All of these patients remained healthy over a mean follow-up period of about four years. This group of patients was compared to a second group of 28 patients who also were under 50 years of age, but who had initial visual acuity in the affected eye less than 6/12. These patients had a variable visual outcome. In addition, they had a higher prevalence of systemic hypertension over the follow-up period than did a group of age-matched control subjects. An additional comparison was made to a group of 26 patients with visual acuity of 6/12 or better in the affected eye but who were over 50 years of age. Forty-six per cent of these patients had final visual acuity less than 6/12, and they had a higher prevalence of systemic vascular disease than did a group of age-matched control subjects.

Adult↗