Development and validation of a visual acuity chart for Australian Aborigines and Torres Strait Islanders

Portal hypertension syndrome is a common evolutive complication of several hepatic and extrahepatic diseases, being liver cirrhosis responsible for more than 80% of cases. When diagnosed it has prognostic value because of the high incidence of hemorrhagic, metabolic and infectious complications that these patients may develop. Clinical suspicion must be confirmed by objective complementary studies that provide information about the etiology and severity of the disease. In this review article we describe the contribution of ultrasonography in the evaluation of patients with portal hypertension as an objective diagnostic method and the usefulness of doppler ultrasound in the non-invasive hemodynamic assessment of the splanchnic and portal circulation.     

Setting an uncorrected visual acuity standard for police officer applicants

The Madelung deformity can result in pain and decreased function of the wrist and hand. None of the surgical techniques available has been shown consistently to improve grip strength, range of movement or relieve pain. In this prospective study we have treated 18 patients with the Madelung deformity (25 wrists) by wedge subtraction osteotomy of the radius and shortening of the ulna. Our results show statistically significant improvement in grip strength and range of movement of the wrist and forearm. Pain improved in 80% of the patients and 88% were satisfied with the appearance. One patient had a wound infection and another developed reflex sympathetic dystrophy. Two had some recurrence due to continued growth of the ulna and it is recommended that the procedure be delayed until skeletal maturity, or else combined with epiphysiodesis of the ulna.     

Automated clinical visual acuity testing

We developed a method for testing visual acuity using a general-purpose microcomputer which displays visual acuity targets on a television monitor, controls a staircase psychophysical testing procedure, and provides a printed record of mean visual acuity and standard deviation. This automated procedure can be used to increase the precision of clinical visual acuity testing and to determine if changes in a patient's visual acuity are statistically significant.     

Comparison of measures of visual acuity in infants: Teller acuity cards and sweep visual evoked potentials

PURPOSE: This study compares the development of acuity in the same infants during one testing session using Teller acuity cards (TAC) and sweep visual evoked potentials (sVEP). We asked whether different testing methods in two centers would produce different developmental time courses. METHODS: Forty-eight infants were tested in two centers. The standard procedure for TAC was used. For sVEP acuity, the amplitude response curve derived from time-locked cortical activity was used to extrapolate to zero response, giving an acuity estimate for each infant. RESULTS: sVEP acuity was generally higher than TAC acuity. The rate of development was steeper for TAC than sVEP acuity with TAC starting at a much lower level. The ratio of sVEP to TAC acuity decreased exponentially with age reaching an asymptote of about 1.44 at 6 months. CONCLUSIONS: Results were indistinguishable between centers suggesting that comparison of acuity measures obtained using variations of these methods across centers is possible.     

Subjective and objective visual acuity testing techniques

The Catford apparatus for determining the objective visual acuity was elevated with 20 normal (20 eyes) and 40 abnormal (75 diseased eyes) patients. The vision of the normal individuals was fogged with neutral-density filters and convex lenses. Eyes with normal or near normal vision showed good correlation between optokinetic response and visual acuity, but no correlation was observed in eyes with poor vision. These findings, which vary from those of Catford, indicate that objective methods of visual acuity testing using a nystagmoid response do not appear useful for general clinical purposes.     

Dynamic visual acuity as related to age, sex, and static acuity.

What effects ability to follow visually a moving target? How about static acuity? Using equipment, including slides, to study static acuity, with 236 Ss, it was concluded that this does not predict it. "The exact nature of those factors other than static acuity that influence dynamic acuity are not yet known, but it is probable that they involve the efficiency of the entire oculo-motor system." From Psyc Abstracts 36:01:3LK11B. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Testing of visual acuity in young children: an evaluation of some commonly used methods

In a comparative study of screening tests for visual acuity in young children, two groups of children were presented with three different tests. In the younger group (three to five years) three single opto-type tests were compared: Sheridan's five and seven letter matching test, the Fooks test and the E card test. The Sheridan test gave the best results and the E card test was found to be unsuitable for this age-group. The Fooks is an attractive test but was less sensitive in the detection of defects than the Sheridan test. In the older group (five to seven years) a single opto-type test, the Sheridan-Gardiner test, was compared with the E chart and the Snellen chart. The Sheridan-Gardiner test was found to have limitations in the detection of defects, including amblyopia, therefore results obtained by this method should not be considered to be directly comparable with those of the Snellen chart. The E chart gave good results in the detection of defects and there was less lateral confusion than had been expected. It has disadvantages, but there is still a place for its use in the screening of normal school-age children. The Snellen chart was the most effective test in the detection of defects, but not all the children were able to co-operate in its use. It is concluded that where it is possible to use the Snellen chart it should always be the method of choice.     

Effect of levodopa therapy on visual evoked potentials and visual acuity in amblyopia

Between 10 and 11 years after children were vaccinated with Vi capsular polysaccharide of Salmonella typhi or meningococcal A + C control vaccine in a double blind randomized trial, we traced 83 subjects, aged 16-20 years. A blood sample was taken for determination of Vi antibody titres in both groups by radioimmunoassay. TO and TH titres were also done to assess if the participants had had recent exposure to typhoid fever. Fifty-eight percent of subjects in both groups had protective levels of Vi antibody against Salmonella typhi (a titre greater than 1 microgram ml-1). There was no significant difference in the levels of Vi antibodies in the cases versus the controls (p = 0.5). Two of the children who had received meningococcal A + C vaccine had recently had typhoid fever. Our data show that adolescents in typhoid endemic areas have high levels of Vi antibodies regardless of previous vaccination status, suggesting that Vi antibodies are acquired in adolescence by a large percentage of the population in this area. Moreover, Vi vaccination has led to ongoing antibody production in greater than 50% of Vi vaccinated children in an endemic area for a period of 10 years. Ongoing antigenic exposure may have contributed to these antibody levels.     

Table for assessing visual acuity in children]

The effect of vegetable (peach kernel) oil on the somatic development and puberty of female rats was studied. The oil was injected (0.2 ml) once intramuscularly into the prepuberty (aged 35 days) or (at the age of 31-35 days) five times. The oil inhibited dose-dependently the somatic development of the rats before puberty. It inhibited the ovarian endocrine function, significantly delayed the initial (opening of the vagina) and terminal (ovulation) stages of puberty or suppressed it completely (in 30% of cases).     

New design principles for visual acuity letter charts

This paper intoduces new principles for the design and use of letter charts for the measurement of visual acuity. It is advocated that the test task should be essentially the same at each size level on the chart. Such standardization of the test task requires the use of letters of equal legibility, the same number of letters on each row, and uniform between-letter and between-row spacing. It is also advocated that, combined with the test task standardization, there should be a logarithmic progression of letter size. Charts incorporating these design features have been made. These charts facilitate the use of nonstandard testing distances which might be used when there is low visual acuity, when examination room layout prevents testing at the standard distance, or when it is necessary to validate visual acuity scores or detect malingering. Adjusting the visual acuity score according to the chosen testing distance is simplified by the use of logarithmic scaling.     

Theories of visual acuity and their physiological bases.

An orientation into the problem of visual acuity and of the size and distribution of retinal receptors precedes a discussion of the principal theories of visual acuity. The 2 static theories covered are Hartridge's and Hecht's, including a critique of Hetcht's theory where evidence is cited that fails to support his position. The 2 dynamic theories discussed are those of Weymouth and his colleagues, and of Marshall and Talbot. The Marshall-Talbot theory, accounting for visual phenomena other than acuity alone, is viewed as the best existing theory, and is evaluated in terms of the principal physiological mechanisms on which the theory is based. 84 references. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Illuminated near card assessment of potential acuity in eyes with cataract

OBJECTIVE: This study aimed to determine the accuracy and potential role of the illuminated near card (INC) for predicting visual outcome after cataract surgery in eyes with and without comorbid disease. STUDY DESIGN: A consecutive case series. PARTICIPANTS: A total of 101 preoperative patients with cataracts participated. MAIN OUTCOME MEASURES: Accuracy of predicted postoperative distance acuity was measured. METHOD: The preoperative acuity obtained with the INC was compared by linear regression to the postoperative INC acuity and the postoperative distance acuity for 100 consecutive eyes undergoing cataract surgery. Variables analyzed were preoperative distance acuity and the presence or absence of comorbid disease. RESULTS: The preoperative INC acuity was significantly predictive of postoperative INC (P = 0.0005) and postoperative distance (P = 0.0007) acuities for the 100 eyes studied. For the subgroup of 15 eyes with 20/200 or worse, the preoperative INC acuity was not predictive of postoperative INC acuity (P = 0.8673) or postoperative distance acuity (P = 0.8789). For the 21 eyes with comorbid disease, the predictions were more accurate for postoperative INC acuity (P < 0.0001) and postoperative distance acuities (P < 0.0001) than for 64 eyes without comorbid disease: postoperative INC acuity (P = 0.0051), and postoperative distance acuity (P = 0.0046). The INC predicted postoperative distance acuity to within two lines in 98% of eyes when preoperative distance acuity was 20/100 or better. When the preoperative distance acuity was 20/200 or worse, the postoperative distance vision was predicted to within two lines in only 53% of the eyes. CONCLUSION: The INC can be a useful adjunct for predicting postoperative distance acuity in eyes with cataract that have preoperative distance acuity of 20/100 or better, particularly in eyes with comorbid disease, in which the clinical judgment of vision potential may be difficult.     

Study of "retinal" visual acuity in eye diseases

Nitrobacter agilis was grown autotrophically on nitrite, mixotrophically on nitrite together with either acetate or pyruvate and heterotrophically on acetate and casamino acids, pyruvate and casamino acids or pyruvate and nitrate. The enzymatic activities differed most in the key enzymes of lithotrophic metabolism. Nitrite oxidase was repressed 90% in 10 days after transition to heterotrophic growth and was no longer detectable after several transfers. The induction of nitrite oxidase began after a lag of 2 days and reached the autotrophic level after 7 days when pyruvate was the carbon and energy source and after 9 days using acetate.     

Spatial frequency and light-spread descriptions of visual acuity and hyperacuity

Resolution (visual acuity) and differential spatial localization (hyperacuity) targets were selected to allow rigorous psychophysical measurements as well as ready expression of both their spatial frequency spectrum and their retinal image light distribution. Thresholds were about 1 arc min for acuity and 4-6 arc sec for hyperacuity. As is consistent with the reciprocal relationship between the space and spatial frequency domains, the small locally restricted spatial differences between just distinguishable patterns are represented in the frequency domain by equally small differences, which are distributed over the entire spatial frequency spectrum. While they occur in many test situations, phase variations of spatial frequency components are not necessary for achieving optimum acuity and hyperacuity.     

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.     

Evaluation of visual acuity of small children with preferential looking methods

With preferential looking (PL) techniques, especially the Acuity Card Procedure (Teller Acuity Cards), the visual acuity in small children can be determined. PL-testing was used in 294 children in the Strabismus and Amblyopia Department of the Ophthamology Hospital in Kraków. These children had been directed from other ophthalmologic departments. Almost all of them showed general retardation and their visual acuity could not be tested with traditional methods. The testing was considered positive when the visual acuity of each eye could be determined separately. Such result was obtained in 230 children (78.2% of all patients). The remaining group consisted of 59 children (20.0%) who were tested only binocularly and 5 children (1.8%) by whom no testing was possible.