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At least 1,405 records · Page 78Linked to original sources
PubMed1965

VISUAL ACUITY OF ESSENTIAL FATTY ACID-DEFICIENT RATS.

1. Rats were maintained on a diet deficient in fat and on a normal diet of rat cubes. 2. Rats were trained to discriminate between vertical and horizontal striations. The minimal stripe width that could be used for discrimination was determined. 3. In bright illumination (0.7 or 4.5 ft.lamberts) both deficient and normal rats had the same ability to discriminate between black and white stripes. 4. With an illuminance of 0.002 ft.lambert, supplemented rats could discriminate as efficiently as at 0.7 ft.lambert, but deficient animals were unable to discriminate at 0.002 ft.lambert. 5. Control rats had 14% of docosahexaenoic acid in their retinal fats but the deficient rats had only 1%. 6. Deficient animals had no vitamin A stores in the liver whereas the control animals had about 190 i.u./g. 7. The visual acuity of the rats used was about 45' of arc.

Adaptation, Ocular↗
PubMed1997

Visual acuity in extremely low birth weight infants.

The increased viability of extremely low birth weight (ELBW) infants (those weighing less than 1,000 g) and the associated increased risk of visual impairment has highlighted the need for reliable indices of visual functioning for this population. By use of the Teller Acuity Cards, we assessed grating visual acuity in 26 survivors of extreme prematurity (corrected age, 2-42 mo) and found that although most scores were within the normal range, they were significantly lower than those of full-term infants of equivalent postconceptional age, especially after 9 months of age. Moreover, the number of complications in the neonatal period (especially bronchopulmonary dysplasia) and the Neonatal Medical Index classification were associated with below-average visual acuity in infancy and early childhood.

Birth Weight↗
PubMed1991

Prolonged electro-retinal response suppression (PERRS) in patients with stationary subnormal visual acuity and photophobia.

Neural adaptation to light stimulation in the dark-adapted retina can be demonstrated by double-flash electroretinography. The first flash is a conditioning flash, the second flash is the test flash. Interstimulus intervals are in the range of 0.2 to 30 seconds. Suppression of the response to the test flash is assumed not to be related to photopigment regeneration, as in normal human subjects the recovery after strong conditioning flashes is completed in about 2 seconds. In this paper we demonstrate the results of double-flash electroretinography on four patients, two of whom are brother and sister. Each of them showed a five- to ten-fold prolonged suppression time compared to normal measurements. Clinical aspects of all the patients were a stationary, though fluctuating, subnormal visual acuity of about 0.5, some photophobia, and difficulties in adaptation to changes in luminance levels. We assume that the PERRS indicates changes in the restorative reactions to phototransduction in the photoreceptors, or in the neural transmission mechanism, either in the rod-driven lateral inhibitory neural processes or in the cone-driven rod inhibitory processes, caused by a cone dysfunction.

Adult↗
PubMed1982

[Variability of visual acuity, dark adaptation and electroretinogram in retinitis pigmentosa].

Clinical and electrophysiological records are of particular importance in tapetoretinal degenerations. In the absence of therapy they are at least a help in establishing a differential diagnosis and a scale of progression of the disease; these in turn lead to improved counselling possibilities. In a retrospective study of 289 patients a great variability of ophthalmoscopic, functional and electrophysiologic findings was observed. The variability was seen both in individual examination of patients of all ages at one point in time, and in genetic pattern, penetrance and expressivity, Criteria for autosomal recessive inheritance were established in 21.3% and for simplex cases in 51.6%. Constriction the retinal vessels was the most reliable ophthalmoscopic finding, seen in 74% of the cases of RP. In 68% of the cases the onset of symptoms started before the age of 20. In 62% of RP patients the visual acuity remained 0.4 or better up to the sixth decade of life. In 40% of the cases the dark adaptation threshold was normal or raised only by up to 1.5 log units. The ERG was absent in 70%, residual in 10%, and subnormal in 20% of RP patients. The residual and subnormal ERGs showed predominantly rod involvement in 77%, equal rod and cone involvement in 17%, and chiefly cone involvement in 6% of 95 cases. The most common associated abnormalities were found to be cataract in 33% and myopia in 22%. (Detailed data on impairment of visual fields and on ERG analysis are published elsewhere: Gurewitsch, K., G. Niemeyer: Rod/cone separation by electroretinography, fundus changes and visual fields in retinitis pigmentosa. In: Techniques in Clinical Electrophysiology of Vision. G. Niemeyer and C. Huber (eds). Docum. Ophthal. Proc. Ser., in press).

Adolescent↗
PubMed1988

Morning-to-evening change in refraction, corneal curvature, and visual acuity 2 to 4 years after radial keratotomy in the PERK Study.

The authors previously reported morning-to-evening changes in ophthalmic measurements at 3 months and at 1-year after radial keratotomy in a self-selected group of patients in the Prospective Evaluation of Radial Keratotomy (PERK) study. Fifty-two patients included in the earlier study were examined again between 2 1/2 and 4 years after surgery before 10:00 AM and after 5:30 PM on the same day to determine if the changes persisted beyond 1 year after surgery. Between the morning and evening examinations, 31% of the eyes had an increase in minus spherical equivalent power of the manifest refraction of 0.50 to 1.50 diopters; 12% had a change in cylinder power of 0.50 to 1.00 D; 19% had a decrease in uncorrected visual acuity of two to five Snellen lines; and 29% showed central corneal steepening by 0.50 to 1.00 D. Thus, in some patients, morning-to-evening fluctuation persisted until 2 1/2 to 4 years after radial keratotomy.

Circadian Rhythm↗
PubMed2006

Age-related changes in visual acuity, learning and memory in C57BL/6J and DBA/2J mice.

The DBA/2J mouse is a model of age-related pigmentary glaucoma in humans. Visual detection, pattern discrimination and visual acuity were evaluated in DBA/2J, C57BL/6J, B6.mpc1d (a C57 congenic strain) and D2.mpc1b (a D2 congenic strain) mice at 6, 12, 18 and 24 months of age. Mice were also tested in the Morris Water Maze and olfactory discrimination learning task. At 6 months, DBA/2J and D2.mpc1b mice outperformed C57BL/6J and B6.mpc1d mice in the visual detection task and there were no strain differences in performance on the water maze. At 12, 18 and 24 months, C57BL/6J and B6.mpc1d mice outperformed DBA/2J and D2.mpc1b mice in the vision tasks and in the water maze. Strains did not differ in the olfactory learning task. Therefore, loss of visual function occurs between 6 and 12 months of age in DBA/2J mice. Strain differences in visual task performance accounted for a significant proportion of the variance in measures of learning and memory in the water maze at 12, 18 and 24 months of age.

Aging↗
PubMed2003

Developmental plasticity of mouse visual acuity.

Monocular deprivation in mice between postnatal days 19 and 32 has been reported to significantly shift ocular dominance within the binocular region of primary visual cortex; however, it is not known whether visual deprivation in mice during this physiologically defined critical period also results in amblyopia, as it does in other mammals. We addressed this uncertainty by psychophysically assessing in adulthood (postnatal day 70 or older) the grating acuity of normal and monocularly deprived mice, using the Visual Water Task. The visual acuity of mice tested with their nondeprived eyes was equivalent to that of normal mice ( approximately 0.5 cycles/degree); however, acuity measured with eyes monocularly deprived of vision transiently between postnatal days 19 and 32 was reduced by over 30% ( approximately 0.31 cycles/degree). Identical binocular deprivation produced a significant, but smaller, decrease in acuity ( approximately 0.38 cycles/degree). The effects of monocular and binocular deprivation were long lasting and occurred only if visual deprivation occurred between postnatal days 19 and 32. These data indicate that the deleterious effects of early visual deprivation on visual acuity in mice are similar to those reported in other mammals, and together with electrophysiological evidence of ocular dominance plasticity, suggest that the mechanisms of mouse visual plasticity are fundamentally the same as that in other mammals. Therefore, the mouse is probably a good model for investigating the basic cellular and molecular mechanisms underlying visual developmental plasticity and amblyopia.

Age Factors↗
PubMed2005

Deep lamellar endothelial keratoplasty visual acuity, astigmatism, and endothelial survival in a large prospective series.

PURPOSE: To report the 6-month results for the treatment of endothelial dysfunction in a large, prospective series of deep lamellar endothelial keratoplasty (DLEK) procedures. DESIGN: Prospective, noncomparative, interventional case series. PARTICIPANTS: One hundred eyes of 88 patients with corneal edema from Fuchs' dystrophy and pseudophakia. METHODS: A limbal, scleral, partial-depth incision provided access for a deep lamellar corneal pocket dissection. Two eyes were converted to penetrating keratoplasty (PK) at the time of DLEK surgery because of poor dissections. Of the 98 eyes that had completed DLEK surgeries, 36 eyes received a large-incision technique (9-mm scleral access incision) and 62 eyes received a small-incision technique (5-mm scleral access incision). A 7.5- to 8.0-mm posterior lamellar disc of recipient tissue then was excised and replaced through the pocket with a similar size donor disc containing healthy endothelium. A temporary air bubble in the anterior chamber was used for donor tissue adherence, and no surface corneal incisions or sutures were necessary. MAIN OUTCOME MEASURES: Preoperative and postoperative best spectacle-corrected visual acuity (BSCVA), manifest refraction (MR) astigmatism, and endothelial cell density (ECD) were evaluated prospectively. RESULTS: At 6 months after surgery, all 98 DLEK corneas were clear and the grafts were healed in good position. The mean BSCVA was 20/46, with a range between 20/20 and 20/400. The average MR astigmatism was 1.34+/-0.86 diopters (D), representing an average change in astigmatism from before surgery of +0.28+/-1.08 D (P = 0.013). The average ECD at 6 months was 2140+/-427 cells/mm2, representing a mean cell loss from preoperative donor cell measurements of 25%. CONCLUSIONS: The DLEK procedure, with its absence of corneal surface incisions and sutures, preserves the normal corneal topography, minimizes astigmatism, and provides a healthy donor endothelial cell count and function. The DLEK procedure represents a reasonable alternative to PK, and compared with historical PK data, offers superior refractive outcomes in the treatment of endothelial dysfunction.

Aged↗
PubMed1993

Binocular enhancement of visual acuity.

Using a computerized test system, we compared binocular and monocular visual optotype acuity, varying both contrast and contrast disparity between the two eyes. When contrast was the same in the two eyes, binocular acuity was better than best monocular acuity by an average of 0.045 log minimum angle of resolution, or 11%. When contrast differed in the two eyes, binocular acuity in most but not all cases was still better than the monocular acuity of the eye that received the higher contrast. This binocular advantage became smaller but remained significant as contrast disparity became larger. These results are most simply explained by threshold contrast summation of high-spatial-frequency letter components.

Adult↗
PubMed2006

Metrics of retinal image quality predict visual performance in eyes with 20/17 or better visual acuity.

PURPOSE: The purpose of this study is to determine the ability of single-value metrics of retinal image quality of the eye to predict visual performance as measured by high (HC) and low (LC) -contrast acuity at photopic (P) and mesopic (M) light levels in eyes with 20/17 and better visual acuity. METHODS: Forty-nine normal subjects in good health ranging in age from 21.8 to 62.6 with 20/17 or better monocular high-contrast logarithm of the minimum angle of resolution (logMAR) acuity served as subjects. Wavefront error through the 10th Zernike radial order over a 7-mm pupil was measured on each test eye using a custom-built Shack/Hartmann wavefront sensor. For each eye, 31 different single-value retinal image quality metrics were calculated. Visual acuity was measured using HC (95%) and LC (11%) logMAR at photopic (270 cd/m) and mesopic (0.75 cd/m) light levels. To determine the ability of each metric of retinal image quality to predict each type of logMAR acuity (P HC, P LC, M HC, and M LC), each acuity measure was regressed against each optical quality metric. RESULTS: The ability of the metrics of retinal image quality to predict logMAR acuity improved as luminance and/or contrast is lowered. The best retinal image quality metric (logPFSc) accounted for 2.6%, 15.1%, 27.6%, and 40.0% of the variance in P HC, P LC, M HC, and M LC logMAR acuity, respectively. CONCLUSIONS: In eyes with 20/17 and better P HC acuity, P HC logMAR acuity is insensitive to variations in retinal image quality compared with M LC logMAR acuity. Retinal image quality becomes increasingly predictive of logMAR acuity as contrast and/or luminance is decreased. Everyday life requires individuals to function over a large range of contrast and luminance levels. Clinically, the impact of retinal image quality as a function of luminance and contrast is readily measurable in a time-efficient manner with M LC logMAR acuity charts.

Adult↗
PubMed1974

Visual acuity.

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Accommodation, Ocular↗