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Results for “Visual Acuity”

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PubMed1997

[Correlation analysis between visual acuity and sitting postural parameters of young students].

The relationship between failing eyesight and the sitting posture of young students while studying was studied quantitatively. Among the 19 students who participated in this study, 9 were classified as emmetropic and 10 were myopic. The mean age was 13.2 +/- 2.2 (mean +/- standard deviation) years. Viewing distance, neck angle, viewing angle, vertical gaze direction, and ocular surface area while studying were measured from the lateral and frontal view images of video recordings of the posture. Viewing distance, accommodative power, neck angle, viewing angle, near point, and log transformed visual acuity showed significant differences between these two groups (p < 0.001). Viewing distance of myopes (15.0 +/- 1.9 cm) (mean +/- standard desviation) is shorter than that of emmetropes (30.2 +/- 4.1 cm). Accommodative power of myopes was lower than that of emmetropes. Correlation analysis revealed that the viewing distance of students significantly correlates to neck angle, viewing angle, accommodative power, near point, and visual acuity (p < 0.01). It can be surmised that the failing eyesight of young students results from postural problems such as shortness of viewing distance and increased neck flexion.

Accommodation, Ocular↗

PubMed2006

Laceration and partial dislocation of LASIK flaps 7 and 4 years postoperatively with 20/20 visual acuity after repair.

PURPOSE: To report two cases of late ocular trauma resulting in laceration of corneal flaps 7 and 4 years (cases 1 and 2, respectively) after LASIK. METHODS: A 49-year-old man sustained laceration of the flap and interface foreign body debris from construction material in the right eye 7 years after uneventful LASIK (case 1). A 33-year-old man had partial dislocation of the flap 4 years after LASIK in the left eye (case 2) due to a penetrating wood chip accident. Surgical procedures were performed to remove the foreign bodies and reposition the flaps. RESULTS: In case 1, postoperative uncorrected visual acuity (UCVA) was 20/25 with manifest refraction of -0.50 -0.50 x 110 corrected to 20/20. In case 2, UCVA was 20/20 with piano refraction after LASIK retreatment. CONCLUSIONS: Corneal LASIK flaps are susceptible to penetrating trauma, which can occur >7 years after the procedure. Proper everamanage ment of the trauma and LASIK flap can restore excellent visual acuity.

Adult↗

PubMed2006

Bidirectional modifications of visual acuity induced by monocular deprivation in juvenile and adult rats.

Recent electrophysiological studies of rodent visual cortex suggest that, in addition to deprived-eye depression, monocular deprivation (MD) also shifts ocular dominance by potentiation of open-eye responses. We used computer-based, two-choice discrimination tasks to assess the behavioral significance of these findings in rats. As expected, prolonged MD, from postnatal day 21 until adulthood (>150 d) markedly decreased visual acuity through the deprived eye. However, we also found that the acuity through the nondeprived eye was significantly enhanced compared with normally reared controls. Interestingly, when the deprived eye was opened in adults, there was a gradual but incomplete recovery of acuity in the deprived eye preceded by a loss of the enhanced acuity in the nondeprived eye. These changes were reversed by again reclosing the eye. These findings suggest that the bidirectional changes in visually evoked responses after MD are behaviorally meaningful and that significant plasticity is exhibited well into adulthood.

Age Factors↗

PubMed2004

Corticosteroid treatment for melanoma-associated retinopathy: effect on visual acuity and electrophysiologic findings.

BACKGROUND: Visual disturbance in the course of melanoma is rare. Specific localized metastases and drug toxic effects are frequently the cause. Recognition of a retinopathy raises several questions when the diagnosis of melanoma-associated retinopathy (MAR) can be confirmed. Descriptions of such patients in dermatologic literature are rare and deserve attention because therapeutic decisions are mandatory. OBSERVATIONS: A 70-year-old woman had a first melanoma in 1985 and a second primary melanoma in 1994. Axillary lymph node involvement occurred in November 2000, leading to surgery and chemotherapy. In December 2001, she had sudden bilateral visual loss, with shimmering blobs of color and flickering photopsias. Computed tomography and cerebral magnetic resonance imaging ruled out localized tumor on the eyes or optic nerves or evolution of disease. Ophthalmologic examination revealed a bilateral posterior uveitis, with hyalitis and progressive destruction of retinal pigment. The electrophysiologic data confirmed the diagnosis of MAR. Symptoms improved after systemic corticosteroid therapy, with no relapse after tapering doses despite worsening of melanoma. CONCLUSIONS: As a rare paraneoplastic visual syndrome possibly leading to blindness, MAR is characterized by bipolar cell involvement without photoreceptor cell impairment. Also, MAR is linked to the presence of autoantibodies directed against melanoma antigens that cross-react with the rod bipolar cells of the retina. Corticosteroid therapy is rarely beneficial. Our case of MAR is noteworthy because it involved a woman, was associated with an uveitis, and improved with corticosteroid therapy.

Adrenal Cortex Hormones↗

PubMed1977

Speedy assessment of visual acuity in amblyopia by the evoked potential method.

As an objective means of assessing visual acuity in young children and of monitoring acuity changes during occlusion therapy, the value of conventional evoked potential recording is restricted by lengthiness and by variability. This article describes one way of circumventing these disadvantages. A graph of evoked potential amplitude versus stimulus check size was continuously plotted while the child viewed a rapidly-oscillating chequerboard pattern whose check size was slowly zoomed up and down. Empirically, the shape of this graph gives an index of acuity and of the acuity difference between the amblyopic and fellow eye. The child's attention could be held for the 2-4 min required by superposing a movie cartoon on the chequerboard pattern, though the movie had a negligible effect on the chequerboard evoked potentials. The briefness of the procedure had the additional advantage of reducing variability.

Amblyopia↗

PubMed1987

Digital visual acuity test using calculator-type numerals with geometric gradation.

The authors have developed a visual acuity test using numeric optotypes with dimensions similar to numerals used in liquid crystal displays (LCDs) or light-emitting diodes (LEDs). Each optotype has the same external configuration to minimize variation in recognition difficulty. The test is designed with geometric gradation and an equal number of optotypes per line, which facilitates the recording of acuity in decimal notation. This allows convenient data entry and computer analysis of acuity results. Chart inversion provides greater flexibility by altering the numeric sequence. This new digital acuity test (DAT) compares favorably to acuity tests that have Sloan or Snellen letters as optotypes.

Humans↗

PubMed1991

[Changes in visual acuity observed in VDT workers in a printing company].

A yearly ophthalmological examination was carried out in 2 VDT worker groups (A-1 and B-1 groups) and 2 control groups (A-2 and B-2 groups). The 4 groups were as follows; workers routinely engaged in both VDT work and key-punch work at a printing company (A-1 group), researchers or office workers handling VDT irregularly at a chemical company (B-1 group), typesetters at a printing company (A-2 group), and office workers at a chemical company (B-2 group). The examination was commenced in the same year in which the workers of A-1 or B-1 group were introduced to VDT work and was carried out for 3 years. Comparison between the first and the last examination on subjective refractive power showed that all the groups had lower refractive powers in the last examination than the first one. The decrease in A-2 group showed the greatest decrease in refractive power among the 4 groups. The decrease in A-2 group was more severe than in the other 2 groups. Before VDT introduction, the workers of A-1 group had been engaged only in key-punch work. Information on naked visual acuities of A-1 group 3 years before VDT introduction was also obtained and compared with those in the first and the last examination. The ratio of workers with a severe reduction in visual acuity evidently increased after VDT introduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2006

Visual detection, pattern discrimination and visual acuity in 14 strains of mice.

Based on the procedure of Prusky et al. (2000, Vision Research, 40, 2201-2209), we used a computer-based, two-alternative swim task to evaluate visual detection, pattern discrimination and visual acuity in 14 strains of mice from priority groups A and B of the JAX phenome project (129S1/SvImJ, A/J, AKR/J, BALB/cByJ, BALB/cJ, C3H/HeJ, C57BL/6J, CAST/Ei, DBA/2J, FVB/NJ, MOLF/Ei, SJL/J, SM/J and SPRET/Ei). Each mouse was tested for eight trials/day for 8 days on each of the three tests. There was a significant strain difference in visual ability in all three tests. Mice with reported normal vision (129S1/SvImJ, C57BL/6J and DBA/2J) and one albino strain (AKR/J) performed very well in these tasks. The other albino strains (A/J, BALB/cByJ and BALB/cJ) took longer to learn the tasks than mice with normal vision and did not reach the criterion of 70% correct. Mice with retinal degeneration (C3H/HeJ, FVB/NJ, MOLF/Ei and SJL/J) performed only at chance levels as did the three strains with unknown visual abilities (CAST/Ei, SM/J and SPRET/Ei). Because many behavioral tasks for rodents rely on visual cues, we suggest that the visual abilities of mice should be evaluated before they are tested in commonly used visuo-spatial learning and memory tasks.

Analysis of Variance↗

PubMed1993

[Visual acuity testing of three-year-old children using Landolt ring and picture targets].

Visual acuity testing using Landolt ring and picture targets (silhouettes of butterfly, fish, bird and tulip), was performed on 184 three-year-old subjects who had received secondary ophthalmic examination at the age of 3 years and 1-3 months, and the results were evaluated. The examinations were feasible on 83.1% of the subjects for the picture test and 76.1% for the Landolt ring test; the picture test being significantly higher. However, when the level was set at 0.5, namely, 0.5 or more were judged as "passing" and less than 0.5 judged as "failing", the Landolt ring test showed a significantly higher rate than the picture test in the number "passing". Specificity and sensitivity were calculated with reference to the clinical findings. Results suggest that the Landolt ring test has a better validity than the picture test and the Landolt ring test could differentiate between good and poor vision. The silhouette of the bird was particularly poor. When using picture targets for testing, the necessity of proper selection of the kind of pictures used is indicated. In the case of use of the Landolt ring, reexamination at the age of 3 years and 6 months or later, or postponement of the examination until age 3 years and 6 months or later would appear to be beneficial for enhancing the feasibility of the test.

Child, Preschool↗

PubMed2006

Relationship between optokinetic nystagmus response and recognition visual acuity.

PURPOSE: The aim of this study was to investigate the relation between recognition visual acuity (RVA) and optokinetic nystagmus (OKN) response exhibited to different bar sizes with varying contrast. METHODS: OKN testing was performed in 52 children aged between 3 and 11 years. The children were evaluated in two groups according to their RVA. Group I consisted of 22 eyes with RVA equal to or better than 0.1 logMAR units. Group II consisted of 30 eyes with RVA 0.2-1 logMAR units. Each subject was seated 60 cm from the screen of Ophthimus device, and was exposed to consecutive black and white stripes of seven different spatial frequencies (0.08-1.6 cycle/degree). The narrowest bar that elicited OKN was identified, and then the OKN contrast threshold at this bar size was established. RESULTS: Twenty-one of the 22 eyes in Group I, and 26 of the 30 eyes in Group II exhibited 1.6 cycle/degree spatial frequency (P=0.287). In Group II, 88.9% of the 18 eyes with RVA 0.2-0.5 logMAR responded at this maximum spatial frequency, whereas the corresponding figure for the 12 eyes with RVA 0.6-1 logMAR was 83.3% (P=0.531). Contrast sensitivity (CS) significantly changed with age in Group I (P=0.006). When the eyes that responded at maximum spatial frequency in the two groups were compared, the mean CS in Group II was significantly lower than that in Group I (P=0.005). CONCLUSIONS: The results indicate no relation between spatial frequency threshold for OKN response and RVA in children. However, the children with RVA deficits had significantly lower CS.

Age Factors↗

PubMed2003

Decreased amplitudes in multiple sclerosis patients with normal visual acuity: a VEP study.

Primary demyelination with relative preservation of axons is considered to be one pathological hallmark of multiple sclerosis (MS), a chronic inflammatory disease of the central nervous system. However, imaging and pathomorphological studies have stimulated a recent re-emergence of interest in the axonal, neurodegenerative aspect of MS pathology. Axonal injury appears to be a key factor of disability and permanent neurological deficit in MS patients. In the present electrophysiological study, visual potentials evoked by pattern reversal (VEPs) were recorded in 25 MS patients with normal visual acuity and unimpaired visual functions. Compared to a control population, VEP amplitudes for two different spatial frequencies were significantly decreased. From this observation, we conclude that an underlying pathological process threatening axonal integrity may not be reliably reflected by clinical parameters due to the distinct ability of the visual system to compensate for axonal loss. Pattern VEP may thus serve as an objective tool to diagnose and to monitor axonal pathology in MS. Focal conduction block due to demyelination as a cause for reduced VEP amplitudes can not be fully excluded, but would appear less likely since latency prolongation in the MS group was moderate compared to controls.

Adult↗

PubMed2005

The effect of supplementation of docosahexaenoic acid and arachidonic acid on visual acuity and neurodevelopment in larger preterm infants.

BACKGROUND: Preterm infants may be born with deficits of both docosahexaenoic acid (DHA) and arachidonic acid (AA), but studies on supplementation of DHA and AA for preterm infants are limited. METHODS: Preterm infants with a gestational age between 30 and 37 weeks who met all the inclusion criteria were enrolled in this double blind, randomized, comparative study. Infants over 2000 g body weight, over 32 weeks of gestation and in full feeding status would enter into the active intervention period of 6 months. Sixteen infants received Neoangelac Plus with AA and DHA supplementation. Eleven infants received Neoangelac without AA and DHA supplementation. The babies had scheduled physical examinations and their cognitive development, visual acuity, and vital signs to be checked. Adverse events were also recorded. RESULTS: The mean Mental Development Index (MDI) scores for the supplementation and non-supplementation groups were 96.1 +/- 8.6 and 91.7 +/- 10.4 respectively at 6 months and 98.7 +/- 8.0 and 90.5 +/- 6.9 respectively at 1 year. The mean Physical Development Index (PDI) scores of these two groups were 102.2 +/- 10.5 and 95.4 +/- 13.2 respectively at 6 months and 98.0 +/- 5.8 and 86.7 +/- 11.1 respectively at 1 year. By repeated measures ANOVA, significant differences existed between groups for MDI and PDI (p = 0.020 and 0.008). However, there were no differences in visual acuity, physical examination variables or vital signs between these two groups. No obvious adverse effects were observed during the study period. CONCLUSION: These results showed possible benefits in the neurodevelopment of larger preterm infants given formula supplemented with DHA and AA.

Arachidonic Acid↗

PubMedDate not supplied

Binocular fixation pattern and visual acuity in children with strabismic amblyopia.

BACKGROUND: A prospective study was undertaken to compare the binocular fixation pattern and presence of amblyopia in strabismic children. METHODS: Fifty-three children with manifest strabismus and the ability to cooperate with an optotype acuity test were examined. The binocular fixation pattern and logMAR visual acuity were recorded by separate, masked observers under standardized conditions. The binocular fixation pattern was divided into four grades from alternation to uniocular fixation. RESULTS: Patients who freely alternated did not have amblyopia, while those who maintained or preferred fixation with a given eye tended to have amblyopia in the nonpreferred eye. CONCLUSION: The binocular fixation pattern can be rapidly assessed with minimal equipment and training. These findings confirm the usefulness of a graded assessment of the binocular fixation pattern in the detection of amblyopia.

Adolescent↗

PubMed1985

The VER as a predictor of normal visual acuity in the adult human eye.

The ability of the evoked potential to predict conventional visual acuity, as measured with a Landolt C test, was investigated for subjects with normal acuities. Both peak-to-trough and Fourier-analysed amplitudes were used. The extrapolation technique assumed curvilinear regression and produced correlations no better than did a method employing amplitude measurements of a single check size of 5.5 min arc (r = 0.67). Assessment of Landolt C acuity by subjective use of the evoked potential stimulus was unable to produce a higher correlation.

Adolescent↗

PubMed1993

[Cystoid macular edema and visual acuity with intracapsular cataract extraction and Choyce anterior chamber lens vs. extracapsular cataract extraction and posterior chamber lens in the partner eye].

A prospective study was conducted on 65 patients who had a cataract operation. One eye had intracapsular cataract extraction (ICCE) with a Choyce-IX anterior chamber lens (ACL) and the fellow eye extracapsular cataract extraction (ECCE) with a posterior chamber lens (PCL). To evaluate the cystoid macular edema (CME), a fluorescence angiogram was recorded on the day of discharge and after 6 months. The severity of the CME was classified in three stages (degrees I-III). At discharge, no eye had CME grade III. CME grade I or grade II was seen in the ICCE group in 23% and in the ECCE group in 7.6%. After 6 months one eye of each group showed CME grade III (1.5%). CME grades I and II were seen after ICCE in 13.8% and 7.8% while the eyes with ECCE presented CME in 6.1% of grade I and of grade II, respectively. Visual acuity (VA) in the eyes with grades I and II CME was the same as in eyes without CME. The VA (median) of the ICCE group was 0.8 and of the ECCE 0.7. Because of infection of the capsular bag (toxic lens syndrome), in one case the PCL together with the capsular bag had to be explanted after 7 months. As for visual acuity and clinically significant CME (grade III), there was no statistical difference between ICCE plus Choyce-IX ACL eyes versus ECCE plus PCL eyes in the same patient.

Aged↗

PubMed1983

Measurement of visual acuity in human and monkey infants: the interface between laboratory and clinic.

The development of visual acuity has been studied in human and monkey (Macaca nemestrina) infants by a combination of preferential looking and operant techniques. Infants of both species demonstrate acuity of about 1 cycle/degree (20/600 Snellen equivalent) near birth. Acuity develops gradually in both species, reaching adult levels at 3-5 years in humans and about 1 year in monkeys. Amblyopiogenic conditions, such as strabismus, occur spontaneously in monkey infants as they do in human infants, and normal monkeys reared under deprivation conditions that mimic amblyopiogenic conditions in humans also become amblyopic. These results help to establish the infant monkey as an animal model for human visual development, and provide an important resource for sorting out the developmental causes of human amblyopia. Three major difficulties and limitations involved in the use of these techniques in clinical settings are described. These are that the testing must be done with standardized equipment by trained personnel; that it is not yet known which kinds of clinical cases can be most usefully evaluated; and that the inherent statistical limitations of the available techniques put them at the outer margin of efficiency for routine clinical use.

Amblyopia↗

PubMed1985

Effects of straylight on visual acuity in pseudophakia.

A new method is presented to study the effect of straylight on visual acuity using a spectacle frame fitted with concentric light-emitting diodes as a glare source. Preliminary results showed that intraocular lenses scatter about 2.3 times more than healthy human lenses.

Cataract↗

PubMed1984

New methods for predicting visual acuity after cataract surgery.

Recent advances in technology have contributed to better evaluation of potential visual acuity in patients with cataracts. The blue field entoptic test, the clinical interferometers, and the Potential Acuity Meter are discussed with respect to their basic principles, clinical uses, advantages, and limitations. There are problems in evaluating these instruments, but their findings can play an important role in clinical decision making.

Cataract Extraction↗