ISSN:0275-5408    

DOI:10.1111/j.1475-1313.1989.tb00933.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Thein vivowettability of soft contact lenses worn by a group of 10 subjects was monitored over a 24‐hour period including 8 hours closed eye. Two types of lenses were tested: Igel 67 (Prima) and Bausch&Lomb 70. They were each worn once in both eyes by all the subjects. Thein vivowettability of the lenses tested was evaluated by measuring the pre‐lens non‐invasive break‐up‐time (NIBUT) and assessing the nature of the pre‐lens tear film structure. The results obtained showed good wettability throughout the study and no difference between the two materials tested, but a significant difference between open and closed eye wear. The tear film was far more stable (p<0.01) immediately upon waking (mean NIBUT 21.2 s) than during open eye wear (mean NIBUT 11.2 s). Also at waking the pre‐lens lipid layer was thicker than during open eye wear and the lens surface had a greater mucous coating. The presence of a more stable pre‐lens tear film at waking was associated with a different tear film structure. We believe these differences in pre‐lens tear film structure are responsible for the greater s

ISSN:0275-5408    

DOI:10.1111/j.1475-1313.1989.tb00934.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The spectral transmittance characteristics of each of thirty‐two solid tint hydrogel contact lenses available in the United Kingdom were investigated using a dual beam spectrophotometer. Good agreement was found with the small number of spectral functions that had previously been published. Lenses with similar colour appearances were seen to differ markedly in terms of their transmittance factors. The importance of visual performance and radiation protection is discussed in the light of the spectral transmittances of the lense

ISSN:0275-5408    

DOI:10.1111/j.1475-1313.1989.tb00935.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The effects of ageing upon the recovery of contrast discrimination following exposure to a bright source of light (glare recovery) were investigated. A total of 65 subjects were tested, with a distribution of ages ranging from 16 to 79 years. Total glare recovery times were relatively constant up to about 56 years of age, after which they became significantly prolonged. Contrast thresholds to a small spot target gradually increased with age.

ISSN:0275-5408    

DOI:10.1111/j.1475-1313.1989.tb00936.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Visual conversion reaction (VCR) is a psychosomatic illness that will occasionally be seen by optometrists and ophthalmologists. This paper discusses some of the possible aetiologies and manifestations of the condition. Investigation and management of children with suspected VCR is discussed. Four case histories are presented in which signs of VCR included amblyopia, reduced accommodation and a deterioration in handwriting. The visual field defects presented include a static quantitative anomaly. Such a defect has not previously been reported.‘Just as you ought not to attempt to cure eyes without head or head without body, so you should not treat body without soul’ (Socra

ISSN:0275-5408    

DOI:10.1111/j.1475-1313.1989.tb00937.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Forced vergence fixation disparity curves were generated for both with and without an accommodative stimulus (accommodative closed and open loop conditions respectively) for fifteen asymptomatic subjects. All subjects exhibited an exophoric shift in fixation disparity for the accommodative open loop condition at the forced convergence side of the curve. No corresponding bias was found at the forced divergence side of the curve. The findings are discussed in terms of the results of previous studies and the existing models of vergence eye movements.

ISSN:0275-5408    

DOI:10.1111/j.1475-1313.1989.tb00938.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The study examines the effect of a near task on immediate post‐task measures of pupil size and accommodative state. The method of quasistatic measurement of accommodation was used and pupillary changes elicited by the accommodative stimulus were simultaneously recorded using an infrared video‐pupillometer. This method requires a short (typically 2 minutes) but strong (up to 10 D in most subjects) near‐vision effort, with the accommodative and pupillary responses being recorded before, during, and after the task. The results show pupil after‐effects to be more pronounced than tonic accommodative after‐effects. Inter‐individual difference in after‐effects is large. The pupil after‐effect was dissociated from the tonic accommodation after‐effect and lasted in some cases for more than 15 minutes. The pupil after‐effect was not masked by darkness. It is proposed that monitoring the changes of pupil is valuable when assessing the after‐effects of

ISSN:0275-5408    

DOI:10.1111/j.1475-1313.1989.tb00939.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

We present an experimental frequency analysis of a neurological control system, the accommodation system, using single sinusoids. Also, by means of continual experimental calibration and full coverage of one subject's dynamic range, we demonstrate an AC nonlinearity saturation, which probably lies in the motor‐response portion of the system; in contrast to the switching‐mode nonlinearity, which probably lies in the sensory‐processing portion. We offer our findings as a basis for further models. In addition, our results can be compared with studies using multiple sinusoids and transients to document how the different aspects of the accommodation system are realized given their different input condi

ISSN:0275-5408    

DOI:10.1111/j.1475-1313.1989.tb00940.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The variation with defocus in the contrast and phase of the retinal image of a grating stimulus is computed from a knowledge of the meaured wavefront aberration of individual eyes. Contrast or modulation transfer is generally lower than in the aberration‐free, diffraction‐limited case, even at a pupil size of 3 mm, and marked spatial phase shifts, which can be seen as sideways shifts in the retinal image, frequently occur. A simple demonstration of these effects is given. The possible significance of the focus‐dependent spatial phase shifts for the phase discrimination of the visual system and accommodation is disc

ISSN:0275-5408    

DOI:10.1111/j.1475-1313.1989.tb00941.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

It is well established that a large variety of psychophysical factors influence the critical flicker fusion frequency (CFF). Several recent studies have examined the relationship between CFF and retinal location with confounding and contradictory results. The aim of this study was to determine the CFF for a number of stimulus sizes and luminances in an attempt to evaluate the interactive effects of these parameters and the quadrantic variation in temporal sensitivity.Retinal sensitivity gradients were measured along the two major oblique meridians out to an eccentricity of 50 degrees. CFF profiles for the 1.724 and 0.431 degree targets were shown to decrease with increasing eccentricity more rapidly in the inferior nasal quadrant (superior temporal retina). No significant difference between superior and inferior visual field temporal processing was evident.

ISSN:0275-5408    

DOI:10.1111/j.1475-1313.1989.tb00942.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY