ISSN:0275-5408    

DOI:10.1111/j.1475-1313.1988.tb01026.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The visual field results from 104 eyes with early glaucomatous loss and 1860 normal eyes have been used to derive the relationship between sensitivity, specificity and the number of test locations in a visual field screening test. A logarithmic relationship was found between sensitivity and the number of test locations and a linear relationship between specificity and the number of test locations. The results indicate that large numbers of test locations are not required to reach high levels of sensitivity and that clinically it might be better to screen all patients with a few stimuli quickly than to examine carefully those patients who meet a precondition such as raised intraocular pressure or abnormal disc appearance.

ISSN:0275-5408    

DOI:10.1111/j.1475-1313.1988.tb01027.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The aim of this study was to investigate the test‐retest reliability of the Arden Grating Test (AGT), and to assess the extent to which any variance in AGT score on retest can be attributed to intra‐subject and inter‐tester differences. Twelve patients with various patholgies and whose contrast sensitivity covered a wide range were each tested twice by six testers. It was shown that variance attributable to testing by different clinicians accounted for approximately 25% of the total variance, and that the 95% confidence limits about any observed score were ± 15 AGT units, which is about one quarter of the total dynamic range of the test. The large range of scores encompassed by the 95 % confidence limits represents considerable unreliability, the consequence of which is a high misclassification rate, i.e. many false positives and false negatives, especially in the context of primary vision screening for which it was de

ISSN:0275-5408    

DOI:10.1111/j.1475-1313.1988.tb01028.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Reading speeds were measured in 18 subjects with normal vision and 10 with low vision for each of 20 experimental conditions with different magnifications and field sizes on the Closed Circuit Television System (CCTV). There was a significant difference between the results for the two groups of subjects. These results suggested that in low‐vision patients with faster reading speeds, minimum magnification for maximum field size on the CCTV would be valid advice. For low‐vision patients who read more slowly, reading speed may improve at higher magnifications despite reduced field s

ISSN:0275-5408    

DOI:10.1111/j.1475-1313.1988.tb01029.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Monocular steady‐state accommodation was measured to harmonically related complex grating patterns and their components to determine the contribution of the various spatial waveforms to accommodative accuracy. Accommodative accuracy was greater for those waveforms containing summed odd‐harmonic spatial components than for those waveforms with specific spatial components either removed or isolated. The results suggest that the contrast gradient produced by the summed waveforms, rather than the presence of any particular subset of spatial frequency componentsper se,was a critical factor for accurate accmmodat

ISSN:0275-5408    

DOI:10.1111/j.1475-1313.1988.tb01030.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

When a young observer attempts to accommodate steadily on a fixed stimulus, the norminally steady‐state response shows small instabilities or fluctuations (sometimes termed microfluctuations or oscillations). These fluctuations typically have an amplitude of a few tenths of a dioptre and a frequency spectrum extending up to a few Hertz. The properties of these fluctuations are described for various viewing conditions: pupil diameter, target vergence, target form, target contrast, and target luminance all influence the frequency spectra of the oscillations, as may anomalies of vision such as amblyopia. The possible roles that the fluctuations might play in the function of the accommodative system are discussed. It is suggested that the higher frequency components around 2 Hzmay arise from the mechanical and elastic characteristics of the lens, zonule and ciliary body. Components at lower frequencies (<0.5 Hz) may be of more significance in the function of the accommodative control syste

ISSN:0275-5408    

DOI:10.1111/j.1475-1313.1988.tb01031.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Mean responses and fluctuations of accommodation were recorded by means of a high‐sensitivity infra‐red optometer over a large dioptric range (+3 to ‐9 D) We found that both the effective absoulute amplitude and the 2 Hz relative activity of fluctuations of accommodation exhibit a maximum within the ‐1 to ‐4 D range of stimulus vergence for which the focus error (lag of accommodation) is minimal, whereas no activity is observed at the subject's near and far points. But the 2 Hz relative activity of accommodative fluctuations provides a better description of the control; this parameter was found to be positively correlated with the sensitivity of the accommodative system to defocus blur (input of the feedback loop), providing support for the active role of these fluctuations in the accommodati

ISSN:0275-5408    

DOI:10.1111/j.1475-1313.1988.tb01032.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

This study investigates whether, during a sustained near‐vision task, the convergent accommodaton (CA) derived initially form the fast (reflex) vergence response is subsequently maintained by tonic (adaptive vergence. CA was examined during the course of a 3 min near‐vision taks (viewing distance 33cm) in 10 emmetropic subject. Vergence was stumulated by the introduction of a 6δ base‐out prism before the right eye while the open‐loop accommodative response of the left eye was measured at approximately 1 s intervals using an objective infra‐red optometer. In a control condition the subject viewed the target through a plano lens (Oδ) The accommodation loop was opened by the subject viewing near‐type through 0.5 mm diameter pinholes. Pre‐ and post‐task measurement of heterophoria was made using a Maddox rod and prism bar. Regression of post‐task heterophoria to the pre‐task value indicated that adaptation to the vergence stimulus had occurred. However, there was no significant reduction in induced CA during the task. As the onset of adaptation does not produce any fall in CA, it is concluded that both reflex and adaptive vergence act as a stimulus to CA. This finding is discussed with regard to models of accommodation

ISSN:0275-5408    

DOI:10.1111/j.1475-1313.1988.tb01033.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The change in pupil centration occurring as the human eye pupil dilates, both naturally in darkness and following the use of a mydriatic drug (cyclopentolate HCl, 1 %), has been measured photographically. In both cases, changes in centration of up to 0.4 mm have been found. Using available ocular wavefront aberration data, modulation transfer curves have been derived for two eyes for centration changes of 0.2 mm. The importance of these changes in the formation of the retinal image, and hence on visual performance, is discussed.

ISSN:0275-5408    

DOI:10.1111/j.1475-1313.1988.tb01034.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

One eye of each of 15 male pigmented rabbits was fitted with a gas‐permeable rigid contact lens. Lenses were worn on a daily basis for an initial period of 7 days with the other eye serving as a control. After this initial period the lenses were removed and both eyes were irradiated with UV‐B (305 nm ± 9 full width half maximum) using either 0.03 J cm‐2or 0.12 J cm‐2which were approximately the epithelial and endothelial damage thresholds for this waveband respectively. The responses of the cornea were followed by microscopy and pachometry. Biomicroscopically there was a dramatic difference in response between contact lens wearing and non‐wearing eyes for the higher radiant exposure, whereas little difference was observed at the lower level. For both levels of radiant exposure there was a significantly less corneal thickness increase in contact lens wearing eyes after UV‐B irradiation. Recovery patterns

ISSN:0275-5408    

DOI:10.1111/j.1475-1313.1988.tb01035.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY