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To our knowledge, this is the first case report wherein visual acuity was lost after peripheral laser iridectomy. Certain facts surrounding this particular event are unusual and may help to broaden our understanding of the mechanism of "snuff".
Two years' experience with a preferential looking technique for visual acuity determination was evaluated. Ninety-three patients were tested during this period, but selected groups (34 patients) were reported on earlier. In 59 patients aged 2 months to 13.75 years 131 testing procedures were performed. Diagnostic groups included uncomplicated strabismus (n = 26), strabismus combined with neurological disturbances (n = 16), neurological disturbances alone (n = 11) and other ocular diseases (n = 6). In addition, several of the children were mentally retarded. In 52 of the 59 patients in this study valuable results were obtained, while no useful information could be gathered from the remaining 7 patients. The findings influenced therapy strategies in 24 patients, and subsequent testing reflected therapeutic effectiveness. The test was successful in 7 of 8 patients referred from other clinics for estimation of visual function. Although established acuity thresholds should be regarded as conservative estimates, and not directly comparable to Snellen letter acuity notations, the preferential looking technique proved to be quite valuable in a paediatric ophthalmology unit. Main indications were amblyopia detection, control of therapeutic measures in strabismics, including pre-operative evaluation, and estimation of visual capacity in children with psychomotor retardation.
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Of the estimated 1 million patients each year in the United States who undergo surgery for media opacities, perhaps 5-10% fail to improve because of pre-existing, undiagnosed retinal and/or optic nerve disease. In this paper, the standard presurgical evaluation (case history, visual acuity, refraction, pupillary response testing, biomicroscopy, ophthalmoscopy, tonometry, visual fields and color vision) and the supplementary presurgical evaluation (entoptic phenomena appreciation, ophthalmic ultrasonography, fluorescein angiography, laser interferometry, potential acuity meter, visual evoked potential, electroretinography, contrast sensitivity and hyperacuity measurements) are reviewed.
PURPOSE: To compare the visual acuity (VA) and contrast sensitivity in 2 types of posterior capsule opacification (PCO) in pseudophakic eyes before and after neodymium:YAG (Nd:YAG) capsulotomy and to evaluate vision test results after Nd:YAG capsulotomy. SETTING: Department of Ophthalmology, Taipei Veterans General Hospital, National Yang-Ming University, Taipei, Taiwan. METHODS: Fourteen eyes with fibrosis-type PCO and 15 eyes with Elschnig-pearl-type PCO were enrolled prospectively. Before and 1 week after Nd:YAG capsulotomy, VA and contrast sensitivity were assessed using the illiterate E version of the Bailey-Lovie chart and the Vistech VCTS 6000 chart, respectively. RESULTS: Before capsulotomy, the mean logMAR acuity in the group with Elschnig-pearl-type PCO was 0.47 +/- 0.32 (SD) and in the group with fibrosis-type PCO, 0.17 +/- 0.07. The difference between the 2 groups was significant (P =.002). After capsulotomy, there was no significant between-group difference (P >.05). Before capsulotomy, the contrast sensitivity was significantly worse (P <.01) at all spatial frequencies in the group with pearl-type PCO, especially at 6 cycles per degree. After capsulotomy, there was no significant between-group difference (P >.05) at any spatial frequency. CONCLUSIONS: After cataract surgery, patients with pearl-type PCO had lower VA and contrast sensitivity than those with fibrosis-type PCO. An Nd:YAG capsulotomy improved the VA and contrast sensitivity in patients with both types of PCO.
We sought to determine whether the dynamic visual acuity (DVA) test, which has been used to measure the function of the two horizontal semicircular canals (SCCs), could be adapted to measure the individual function of all six SCCs using transient, rapid, unpredictable head rotation stimuli (head thrusts) in the direction of maximum sensitivity of each SCC. We examined head-thrust DVA (htDVA) performance in 19 healthy control subjects, five patients before and six patients after plugging of one superior SCC for treatment of superior canal dehiscence, and two subjects with unilateral vestibular deafferentation (UVD) by vestibular neurectomy. We compared htDVA results for each SCC to vestibulo-ocular reflex gains measured using 3-D scleral coil recordings during a passive head-thrust-test paradigm. Individuals with normal vestibular function had similar htDVA scores for each of the six directions (canals) tested (mean 0.058 +/- 0.050 LogMAR). Individuals tested after surgical plugging of one superior SCC were similar to normal for all SCCs except the plugged SCC, which had significantly worse htDVA scores (mean 0.270 +/- 0.08 LogMAR). Individuals with UVD had significantly worse htDVA scores for head rotations maximally exciting any of the ipsilesional SCC (mean 0.317 +/- 0.129 LogMAR) and scores similar to normal subjects for contralesional rotations (0.063 +/- 0.051 LogMAR). These findings suggest that the htDVA test, which does not require scleral coil placement, magnetic field coils, or expensive oculography equipment, can provide a useful quantitative measure of individual SCC function.
Cataract patients whose surgical outcomes were in question were referred for testing by visual evoked potentials, elicited through closed eyelids by a luminance stimulus (flash) that appeared 10 times per second. Visual evoked potentials were rated as normal (predicted acuity of 20/50 or better) or abnormal (predicted acuity of 20/60 or worse). Postoperative Arden and Optronix contrast sensitivities and visual acuities were determined in 37 patients who had no intraoperative or early postoperative complications. Arden grating scores of less than 100 were rated as normal. The optimal and cutoff spatial frequency values were determined for the Optronix scores. Optimal and cutoff values of greater or equal to 1 c/deg and 12 c/deg, respectively, were rated as normal. Visual acuities were considered normal at 20/50 or better. Preoperative visual evoked potentials were quantitatively compared to the postoperative contrast sensitivities and visual acuities by 2 x 2 contingency tables. The accuracy of prediction was 79% for the visual acuities, 62% for the Optronix optimal values, 70% for the Optronix cutoff values and 62% for the Arden gratings.
Behavioural estimates of the visual acuity of the Northern Native Cat (or Northern Quoll)--Dasyurus hallucatus--were made using the Mitchell jumping stand technique. A value of 2.3-2.8 cycles per degree was obtained. This functional acuity compared well with predictions based on the peak ganglion cell density (2600 cells/mm2) determined from the retinal ganglion cell density map.
PURPOSE: This study aimed to determine the relationship between visual function impairment in 776 patients who had extracapsular cataract extraction with posterior chamber intraocular lens implantation and gender, age, preoperative visual acuity (VA) of both the operative and the contralateral eye, and presence of other ocular disease in the operative eye. DESIGN: Retrospective cross-sectional study. PARTICIPANTS: 1139 patients whose medical records were abstracted and who had cataract surgery performed at 1 of 10 participating academic medical centers in 1990. MAIN OUTCOME MEASURE: In the 776 patients who had explicit statements about impairment of visual function documented in their medical records, univariate and multivariable logistic analyses were used to assess the above relationship. RESULTS: The most severe visual functional deficit that justified the cataract operation varied in relation to gender, age, and VA. On bivariate analysis, men were more likely to have impairment with employment, driving, and glare, whereas women were more likely to have impairment with activities of daily living and recreational activities. Significant findings between visual impairment and the independent variables from the logistic regression models included: (1) employment limitation and male gender (odds ratio [OR], 1.92; 95% confidence interval [CI], 1.08-3.40); (2) employment limitation and younger age (OR, 0.12; 95% CI, 0.050-0.28 for ages 70-79); (3) recreational impairment and older age (OR, 2.77; 95% CI, 1.64-4.70 for ages 80+); (4) impairment in performing activities of daily living and female gender (OR, 0.72; 95% CI, 0.53-0.98 for male gender); (5) impairment in performing activities of daily living and worse VA in the operative eye (OR, 5.13; 95% CI, 2.93-9.00 for VA < 20/100); (6) glare-associated impairment and younger age (OR, 0.40; 95% CI, 0.24-0.69 for age 80+); and (7) glare-associated impairment and better VA (OR, 0.16; 95% CI, 0.067-0.38 for VA < 20/100). CONCLUSION: When deciding whether to perform cataract surgery, functional impairment must be considered in relation to the age and the gender of the patient, for the type of functional impairment varies in association with age and gender.
For a sample of college observers, visual performance was assessed with three types of measures: (1) contrast sensitivity for a range of spatial frequency gratings with 4-Hz flicker, (2) contrast sensitivity for a range of stationary wallchart gratings, and (3) dynamic visual acuity (DVA) for a range of target velocities. Within each of these three performance measures, mean results were generally consistent with previous reports. However, across-test comparisons revealed little commonality of processes between either of the contrast sensitivity scores and the dynamic acuity scores. These findings are discussed in terms of the separate contributions to overall visual performance made by the increasingly popular contrast sensitivity function (CSF) and DVA.
The development of visual acuity was studied longitudinally in young kittens, using a modification of the forced-choice preferential looking method (FPL) devised by Teller et al. [Vision Res. 14, 1433-1439 (1974)] for human infants. Acuity, defined as the spatial frequency which yields 70% correct responses by a naive observer, shows a 16-fold increase between 2 and 10 weeks of age. At comparable ages, acuity evaluated by this method falls short of the acuity values obtained with the mumping stand or with electrophysiological methods. FPL acuity estimated with a more lenient criterion (58%) comes close to the resolution of the highest-resolving single cells in the striate cortex. These results suggest that the preferential looking procedure provides a method that can be used in kittens over a wide age range, including ages at which it is impossible to use the jumping stand method.
STUDY OBJECTIVE: To determine the effect of topical anesthetics on visual acuity (VA). METHODS: We studied 66 consecutive patients (73 afflicted eyes) who presented to a university hospital emergency department with the complaint of eye pain. VA was measured before and after patients were treated with proparacaine, a topical ocular anesthetic. RESULTS: After proparacaine instillation, VA was improved in 33 patients (45%), unchanged in 34 (47%), and worse in 6 (8%). CONCLUSION: Patients with eye pain often demonstrate improved VA after the instillation of a topical anesthetic.
OBJECTIVE: The authors sought to determine whether depression influences the measurement of visual acuity (VA) in older persons. METHODS: This was a prospective study, in a geriatric psychiatry inpatient unit. Participants were 32 older patients with major depression. Authors measured VA before and after treatment of major depression, as measured by the Center for Epidemiologic Studies Depression Scale (CES-D). RESULTS: As depression resolved, there was no significant change in VA from admission to discharge. CES-D scores significantly declined from admission to discharge. VA was not correlated with depression severity (CES-D score) either at baseline or at discharge. CONCLUSION: This study found no evidence that depression influenced VA testing in older adults. Additional studies in patients with major eye diseases are necessary to evaluate the generalizability of this finding.
The effect of pilocarpine on visual acuity and on the dimensions of the cornea, anterior chamber, and lens were studied in two groups of subjects. Significant changes in ocular tension, corneal curvature, anterior chamber depth, and lens anterior radius were found in a group of 55 glaucomatous eyes as a result of pilocarpine treatment, but there was no change in corneal thickness. Out of 102 glaucomatous eyes 78 became relatively myopic, and this appears to be due to changes in the dimensions of the lens of the eye similar to those occurring in accommodation, as a result of the effect of the drug on the ciliary muscle. The effect of pilocarpine on anterior chamber depth, area, and volume was studied in 125 eyes using a photographic method, and a significant reduction in the dimensions of the anterior chamber was observed as a result of the administration of pilocarpine. A significant correlation between depth and volume was also noted and the implications of this are discussed.
After stellate ganglion blocks 5 patients with marked decreased visual acuity showed a pronounced increase of same, verified either by Snellens types or automated perimetry.
After slight modification of an electronystagmograph (Jung) an objective estimation of visual acuity was carried out. The optokinetic nystagmus was inhibited by a variable light spot, which was projected in the middle of the screen (Ohm's method). In 95 (161 eyes) of 98 patients the suspected simulation or aggravation was verified.
The performance of 6 domestic hens on a visual acuity task was studied using a spatial discrete-trial conditional discrimination procedure. Gray stimuli and vertical square-wave gratings, ranging in spatial frequency from 1 to 10 cycles per millimeter, were presented in a descending and ascending series of probes. On each trial, either a grating or gray stimulus was presented. Only one spatial frequency of grating was presented during each session. Between probe sessions, training continued at the coarsest grating value. Stimulus discriminability, measured as values of log d, changed with changes in grating spatial frequency for both probe series. Fitted lines described the linear portion of the psychometric functions. Thresholds estimated from the lines generally ranged from four to six cycles per degree, with slightly greater estimates from data from the descending probe series. There were no systematic changes in response bias as a function of grating spatial frequency.
The authors describe a new test for determining the visual acuity in pre-school children. It is a picture-test which is composed by pictures of animals of varying sizes, the child being asked to name them in turn. The six pictures (duck, rabbit, cock, elephant, fish, and butterfly) with an homogeneous density, can be utilized according to several manners-appariement or verbal expression--and several distances: 2,50 m or 5 m. That test gave good results on children aged from three years upwards, however the performances could be increased by prectising exercises.