Monocular simultaneous refraction.
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Humans↗
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Electroretinogram and visual-evoked potential measurements in sheep.
Electroretinogram (ERG) and visual-evoked potential (VEP) recordings were taken from ten Suffolk-cross sheep. Stimuli for VEP were 1.5 flashes of white light/s; ERG stimuli were single flashes. The ERG measurements of the a and b wave latencies and a-to-b amplitude were measured between the lower eyelid and the vertex, with ground on the nuchal crest. The VEP after monocular stimulation were measured between the nuchal crest and the interorbital line, with ground on the vertex. Measurements consisted of the latencies to seven alternating positive and negative peaks P1, N1, P2, N2, P3, N3 and P4, and six amplitudes, P1-N1, N1-P2, P2-N2, N2-P3, P3-N3 and N3-P4. Average latencies for the a and b waves were 13.6 and 28.2 ms; the mean ab amplitude was 131.68 microV. Average latencies for the seven VEP peaks were 35.0, 43.1, 52.8, 64.1, 74.5, 90.4 and 112.2 ms. Mean amplitudes ranged from 3.90 to 8.29 microV.
Animals↗
Visual acuity of the U.S. Navy jet pilot and the use of the helmet sun visor.
Visor wear habits, evaluative comments and vision test data were obtained from interviews of 126 Navy fighter pilots. The interviews revealed that many pilots use their helmet sun visor whenever they fly, some use it only during certain flight operations, and others never use it. Study 1 (conducted at 343 cd/m2) revealed a decrease in low contrast visual acuity attributable to helmet sun visor use in the presence of a glare source. These findings prompted a second study of the visual effects of visor transmittance. Low-contrast spot detection, acuity, and contrast sensitivity were measured at an operationally realistic daytime illumination level (6870 cd/m2) in subjects viewing through filters ranging from 6.3% to 50.1% transmission. (Standard visor transmission is 12 +/- 4%.) Results showed that filter density, and consequently the illuminance reaching the eyes, could be varied over a wide range without critically affecting these visual functions. Prevailing environmental illuminance should be considered when selecting sun visors or sunglasses. These results have implications for optimizing visual performance through visors.
Adult↗
Basic ocular motility assessment.
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Diagnosis, Differential↗
The career impact of keratoconus on Air Force aviators.
Keratoconus causes progressive blurring and distortion of vision, which threatens the career of a military aviator. To assess the impact of keratoconus on flying careers, we reviewed the records of all aviators with keratoconus who have been examined at the United States Air Force School of Aerospace Medicine over the past 23 years. Of the 22 aviators observed for more than three years, 18 were still qualified to fly at their most recent examination. The remaining four aviators were permanently removed from flying duties because of visual dysfunction caused by keratoconus. Of the 22 aviators examined, 15 required hard contact lenses for optimal correction of vision. No aircraft accidents or incidents, attributable to visual factors, were documented. We concluded that the majority of aviators with keratoconus are able to continue their flying careers safely with the aid of spectacles or contact lenses.
Adult↗
Use and non-use of low vision aids by visually impaired children.
The results of this study indicated that children do use and benefit from low vision aids and that the child's need for near low vision aids can be predicted from their age, unmagnified reading performance, and visual field characteristics. The use of distance monoculars is less easily predicted. However, many visually impaired children both in mainstream special units and in schools for the blind are not being supplied appropriate low vision aids (LVAs). Many have not had an LVA assessment within 1 year and others are experiencing difficulties with LVAs that could be eliminated or reduced.
Adolescent↗
Testing visual acuity of children using vanishing optotypes.
To test visual acuity in children, we developed a chart constructed so that the mean Fourier transform of the luminance of the figures on the chart at zero spatial frequency is the same as the background luminance. When the eye reaches its limit of resolution, the figures vanish into the gray background of the chart rather than becoming "blurred" as in conventional visual acuity charts. We compared the number of errors in determining the visual acuity of children aged 3-4.5 years using this high-frequency chart and a standard black-and-white high-contrast chart. Significantly fewer errors were found with the high-frequency chart, suggesting that this type of testing may improve the accuracy of visual acuity measurements in children.
Child, Preschool↗
Presbyopia and the dentist: the effect of age on clinical vision.
Vision is extremely important in dentistry where many clinical tasks requiring fine discrimination are performed. Presbyopia, an inability to focus sharply on near objects, affects all dentists in the later years of their practising lives and may have adverse effects on the practice of dentistry. This study examined the visual acuity of 172 practising dentists using a reduced Snellen chart imaged at 25 cm and 33 cm. Twenty-seven per cent failed the near vision test, having acuity of less than 6/9 at 25 cm, while 18 per cent had acuity of less than 6/7.5 at 33 cm; 96 per cent of those who failed at 25 cm and 93.5 per cent of those who failed at 35 cm were 45 years of age or more. Working distance (operating distance) was found to be significantly greater in dentists over the age of 45 than in a group of undergraduate dental students. No statistically significant relationship between visual acuity and working distance could be demonstrated. Regular examinations by qualified personnel are essential for dentists who should have their eyes checked every 2 years after the age of 40. Dentists should discuss their specific requirements for the practice of dentistry with their eye-care specialist. A suggested minimum standard of visual acuity for practising dentists is 6/7.5 at 33 cm.
Adult↗
[Electrophysiological studies in amblyopia].
The authors describe the methods of recording the visual evoked potentials and of their utilization for investigations in amblyopia. The characteristics of VEP have been analyzed in an amblyopic and a normal eye; analyzed further on were the reciprocal dependencies between an uniocular and binocular records, the phenomenon of suppression and sensitivity to contrast. The authors confirm the suitability of the VEP for objective evaluation of the progress of treatment and for elucidation of the physiopathology of amblyopia.
Amblyopia↗
[The effect of instruction with computers on the functional state of first-graders].
A study is carried out on 64 first grade school children for establishing the effect of computer training on the functional status of principally engaged systems with the purpose to determine the optimum duration of work with video terminal during the school day. The examinations are performed before and after computer lessons in mathematics and Bulgarian language in days with one and two lessons, and with the same subjects taught in the traditional way (control group). Traced are the changes in the accommodation, the eye rheobase, critical frequency of fusing the light flickers, resistance, volume and accuracy of the visual perception, static tremor and excretion of sodium and potassium in the saliva. The data point out to relatively higher pressure at work on video terminal in comparison with the traditional education. This imposes restriction in the duration of the lesson up to 20 minutes. The inclusion of second inconsistent computer lessons in the educational programme has no unfavourable effect on the functional status of the organism.
Adrenal Glands↗
[A new simple instrument for ophthalmologic evaluation of patients with "low vision"].
Authors present specially adapted visual acuity charts for "low vision" patients. For them refraction must be surveyed as often as possible.
Humans↗
[A new evaluation system of 3D vision].
3D vision assessment depends on monocular and binocular factors. In ophthalmology, it is clinically evaluated through the optometric examination which is not exhaustive according to the monocular elements and doesn't take on the visual stimulus quantification. The video and electro-optic displays can meet all these exigencies. The basic principles they share are exposed and then an illustration is given of their performance and their adaptation to the physiologic mechanisms. So is presented a study on the fusion area of heterophoric subjects depending on the stimulus spatial frequencies (the synthetic precisely quantified images shown were circular DOGs). This area is greatly modified following the variety of subject's heterophoria.
Adult↗
[How to follow the visual development in infants under 2 years of age].
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Aging↗
Assessment of accommodative facility using MEM retinoscopy.
Subjective testing of accommodative facility can be difficult with young or nonverbal children, and children with learning problems. A new technique to objectively assess accommodative facility using monocular estimation method (MEM) retinoscopy is described. The objective technique was compared to a subjective assessment of accommodative facility, and the techniques were in agreement 86% of the time. Possible clinical usefulness of the objective procedure is discussed.
Accommodation, Ocular↗
Phoria adaptation in patients with cerebellar dysfunction.
The authors studied phoria adaptation to horizontal base-out prism in 17 patients with well-documented cerebellar lesions. There was no significant difference between mean adaptation measured in the patients and ten normal controls. Individually, normal adaptation was found in 12 patients. Abnormal adaptation was found in five patients, all but one of which had other neurologic lesions. These results suggest that phoria adaptation to base-out prism is not diminished by a cerebellar lesion unless it is accompanied by another nervous system lesion(s).
Adaptation, Ocular↗
Do women and myopes have larger pupils?
It is commonly reported that the pupils of women are larger than those of men and the pupils of myopes larger than those of emmetropes. However, these reports are not supported by experimental procedures using objective measurements, controlled conditions, and adequate numbers of subjects. In this report the open-loop pupil size was measured objectively using dynamic infrared pupillometry in a sample of 48 subjects. Subjects were balanced for age and equally divided between emmetropes and myopes, males and females. The results did not support the contention that females have larger pupils than males or that physiologic myopes have larger pupils than emmetropes.
Adolescent↗
[Rhythmic cyclicity of monocular perception in binocular fixation under haploscopy].
The paper describes results after a study of rhythmic cyclicity of monocular perception in 341 students with normal visual functions in bifixation for far and for near. It was found that cyclicity of monocular perceptions (biorhythms) in healthy persons with binocular vision is the same in bifixation for far both in soft and hard haploscopic conditions. In bifixation for far in haploscopic conditions the rhythms of monocular perceptions are more frequent than for far. Both for far and for near the rhythms of binocular vision are more frequent in women than in men.
Adult↗