摘要:

The difference in extent of movement of the lower lid and of the line of fixation of 107 subjects when the eyes were lowered from the primary plane to the reading position were measured using a stroboscopic camera. The difference in the extent of movement between the two is assumed to indicate the amount by which the lower lid would raise a bifocal contact lens before the pupil. The mean difference was found to be 0.8 ± 0.347 mm. The area of the pupil occupied by the segment based upon each individual pupil size and difference of lid/ fixation movement was also calculated. The mean for the above subjects was found to be 16.9 ± 14.4%. Both the above values are much less than the amounts heretofore predicated for efficient bifocal vision. Other factors, particularly the upper lid's role in the movement of the contact lens translating bifocal, are noted.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

A pattern reversal stimulus (check size 5.5 min arc) was used to elicit visually evoked responses (VER's). The peak to trough amplitude of the VER wave was measured and compared to the subjective visual acuity (Landolt C) in 30 subjects. The recordings were made at 3, 6, and 12 pattern reversals per s. The correlation coefficients are reasonably high (r = 0.81) for both the 3 and 6 reversal rates with a considerably lower correlation coefficient (r = 0.54) for the 12 reversals per s stimulus. Repeatability measurements on a further 6 subjects taken over a 5-week period produced an amplitude coefficient of variation of 13% for the 6 subjects with the 3 reversals per s stimulus.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

There are often large disparities in the way in which visual acuities are reported for groups. A survey of 156 reports published within the last 5 years shows that some researchers report binocular acuity, others best eye, monocular, or mean monocular acuities. Some of these measures may be confounded further with accommodation distance. To ascertain the relation among the various measures of acuity reported commonly, data were obtained from 702 observers. The results indicate that there is a high degree of concordance among the various measures used to report the visual acuity of groups, with many of the correlations in the 0.9 range. It is further shown that a composite measure, based upon mean binocular or best eye acuity, may be a useful means of conveying group differences in visual resolution.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

The effects on dark adaptation of exposure to light presented only in the extreme periphery were significantly greater for observers over the age of 40 years. Increasing the exposure duration from 0.5 to 5 min significantly affected only the older observers.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Eyes of 27 patients with keratoconus and 37 normal persons were examined with a photo-keratoscope. The photokeratoscopic data were analyzed to obtain information about the corneal apex and a comparison between the two groups was performed. The study demonstrates a significant shift in the position of the corneal apex in relation to the visual axis from a superior-temporal position in the normal group to an inferior position without temporal-nasal preference in the keratoconic group. However, the magnitude of the apex displacement (lxa) was equal in the two groups both in the horizontal and vertical direction. The influence of xaon the stability of the central corneal curvature was established by the apex factor (AF). The magnitude of AF depends as well on xaas the corneal shape. In the keratoconic eyes the vertical AF is about 5 times the horizontal AF, whereas in normal eyes the AF is equal in the two meridians. Thus the increasing astigmatism so characteristic for the keratoconic eyes may be caused by unequal alteration in the shape of the horizontal and vertical meridians.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

This study evaluated the effects of head and gaze position on near fixation disparity, phoria, and duction findings. A population of 104 non-complaining subjects divided by age into 3 groups participated in the study. The primary head and gaze position along with two others approximating the positions used for reading by nonbifocal and bifocal wearers were used. A statistically significant effect was found for the phoria data from the young group, but the magnitude was clinically insignificant. Changes in head and/or gaze positions did not significantly affect fixation disparities or duction recovery ranges. Phorias and fixation disparities showed statistically significant increases in exo deviation with increasing age regardless of head and/or gaze position. Nine of 23 presbyopic subjects gave erratic findings during fixation disparity testing and this casts doubt upon the clinical usefulness of this procedure with presbyopes.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

It is well known that induced vertical imbalance will bring about deviation from central fixation in the vertical meridian. This study seeks to determine if vertical imbalance will affect the fixation performance in the horizontal meridian as well. For this purpose, a technique previously developed for monitoring fixation eccentricity was used. The technique, which is based on the effect of fixation eccentricity on border enhancement, is unaffected by adaptive changes in perceived visual direction. The results show a rapid increase in horizontal fixation misalignment with the first increments of vertical prism difference, followed by a slower increase for additional prism differences. When horizontal forced vergence was applied in addition, fixation misalignment increased throughout the range of vertical vergences. Similarly, vertical fusion misalignment was increased by horizontal fusion stress. It was concluded that forced vergence presented in one meridian will amplify any fusion misalignment that might exist in other meridians. This calls for a reevaluation of existing methods of assessing binocular fixation performance.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

The utility of the Melbourne Edge Test (MET) in optometric practice was evaluated by screening 293 consecutive patients who presented for routine eye examination. The MET identified ocular abnormalities in 37 eyes. Of these, 36 also manifested a reduction of visual acuity. The incidence of “false positives” was 1.0%. The MET test failed to detect ocular abnormalities revealed by conventional examination techniques in 29 eyes (4.9%), of which 28 exhibited Snellen acuity losses.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

The accommodative response (AR) to disparity-vergence and blur stimuli was determined for 45 subjects; 15 emmetropes, 15 late-onset myopes (LOM's), and 15 early-onset myopes (EOM's). The accommodative response was measured at approximately 1-s intervals for 50 s using an objective infrared optometer. Disparity-driven accommodation was induced by a 4δ base-out prism at accommodative stimulus levels of 2.50 and 3.25 D. LOM's show significantly higher levels of disparity-induced accommodation when compared with the other two refractive groups. Blur-induced accommodation was produced by increasing the accommodative stimulus from 2.50 to 3.25 D with no concomitant change in vergence stimulus. EOM's exhibit less blur-induced accommodation compared with LOM's and emmetropes. These results are discussed with reference to differences in accommodation-vergence synkinesis between LOM's and EOM's, and in relation to the etiology of late-onset myopia.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

The case presented is that of a patient who developed optic atrophy after a fall involving head trauma in the orbital area. A diagnostic workup including electrophysiological testing and photodocumentation is presented. Testing identified frank optic neuropathy with normal retinal function.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID