The British journal of physiological optics最新文献

An English Electric Valve Co. P8073 light intensifier was set up with a viewing system to assess the performance of retinitis pigmentosa sufferers at low luminance levels. Six subjects had their acuity measured at different luminance levels using a light intensifier initially and subsequently using direct vision. All subjects showed an improvement in acuity using the intensifier compared with direct vision at levels of illumination ranging from 0.25 cd m-2 to 20 cd m-2.

An experiment is undertaken to investigate the relationship between "sighting" and motor dominance. A review of recent work on the neurophysiology of vision is carried out and an attempt to explain ocular dominance using this is made.

This is a survey of the causes of blindness recorded by three students of The City University during a six-week stay at NOOR Eye Institute in Kabul, Afghanistan. The nature of the sample used makes it unsuitable for direct comparison with surveys from other countries. Nevertheless, broad conclusions can be drawn. Severe eye disease is a considerable problem in Afghanistan, in common with other developing countries. The survey included all new patients seen in the outpatient clinic, blind to the extent of being unable to count fingers at more than three metres, in one eye or both. The sample of patients was examined by an ophthalmologist working with our team. A diagnosis was made and various social and demographic questions were asked with the help of an interpreter. In all, 473 patients were examined and included in our survey sample, a very high proportion of the new patients attending the clinic (40.46 per cent). The main causes of blindness were found to be cataract (31.12 per cent), corneal scarring (19.8 per cent), chorioretinal degenerations (6.79 per cent), glaucoma (6.65 per cent) and aphakia (5.52 per cent). Of the major causes of blindness, about forty per cent of the cases were considered remediable, and about thirty per cent could have been prevented. An outstanding difference between the causes of blindness in developed nations and those seen in Afghanistan was the amount of blindness caused by infection, especially in the younger age groups (up to 30 years). Cataract is a major cause of blindness in the older age groups of both societies. People suffering from ocular disease in Afghanistan wait until their sight is badly impaired or lost completely before seeking treatment. This results from a lack of knowledge of what could be done to conserve sight, the irreversible nature of many eye diseases, the distances involved in travelling to the clinic, and even a lack of knowledge of its existence.

An investigation was carried out into the effect of a monocular neutral density filter on the position of the binoculus. Two experiments were used, and it is postulated that the difference in the results obtained is due to the presence of a motor component in one of the experiments.

While sinusoidal grating stimuli are finding increasing application in clinical tests for visual disturbance, the possible effects on the test results of simple defocus of the retinal image, due to refractive or accommodative error, are not always acknowledged. Theoretical considerations and experimental measurements emphasize that the degradation in visual performance due to such defocus effects is minimal when the eye pupil is small and the spatial frequency of the grating test objects is low.

In this review of perimetry the subject is treated in two main sections. Part I discusses developments, particularly during the last thirty years, in classical clinical perimetry including the topics of kinetic and static perimetry, the use of multiple stimuli and the role of automation and objective techniques. Part II describes the development of various special techniques designed for more specific information about visual function. These include reference to the importance of controlling target illuminance, the value of spatial and temporal summation in perimetry and the use of coloured targets. The paper concludes by emphasizing the clinical value of routine field screening and the urgent need for standardization in perimetry.

The records of treatment by the after-image transfer method of 21 children, mainly with strabismus amblyopia, were examined to evaluate the acuity improvement in the short term. There was no significant improvement in 15 cases. In several other patients, an immediate response to the after-image method occurred, but these patients' binocular vision and acuity had deteriorated following previous improvement achieved by other orthoptic methods.