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Biomedical subjects

R J Randle

Publications and source records attributed to R J Randle.

7 recordsLinked to original sources
PubMed1988

Responses of myopes to volitional control training of accommodation.

Twelve young, low myopes were trained to control volitionally their accommodation responses and to achieve clear focus on visual targets moved progressively outward in optical distance. The trainees participated in from 15 to 40 daily training sessions (mean = 28 sessions). All demonstrated volitional control with varying degrees of control authority. Though three of the trainees were unsuccessful, the group achieved a statistically reliable extension of their far points. Post-training optometric examinations were reliably improved over pre-training examinations, but did not appear to be commensurate with the large gains in far-point extension. It was hypothesized that the learned skill may have been 'instrument-specific', i.e. it might not fully generalize to significantly improved post-training binocular performance unless it were accompanied by clinical assistance to transfer the training.

Accommodation, Ocular↗
PubMed1984

Effect of a concurrent counting task on dynamic visual accommodation.

The visual accommodation of four male subjects was selectively recorded over a 3-day period using an objective, continuously recording, infrared optometer to determine the effects of a concurrent counting task on their ability to accommodate to a sinusoidally changing focus stimulus ranging from 0.0 to 3.0 D. There was an increase in their steady-state errors in the direction of negative accommodation of from 0.25 to 0.50 D, but the magnitude of the steady-state error induced by the concurrent task did not change over the three sine wave frequencies used (0.1, 0.2 and 0.4 Hz). The results are discussed in terms of an accommodative "lag" model of sympathetic-parasympathetic arousal induced by superimposing an extraneous mental task.

Accommodation, Ocular↗
PubMed1977

Diurnal rhythms of visual accommodation and blink responses: implication for flight-deck visual standards.

The major purpose of this study was to determine whether 24-h variations in accommodation responses occur and, if they do, whether they should be considered in setting visual standards for flight-deck tasks. A recently developed servo-controlled optometer and focus stimulator were used to obtain monocular accommodation response data on four college-age subjects. No 24-h rhythm in accommodation was shown. Heart rate and blink rate also were measured and periodicity analysis showed a mean 24-h rhythm for both; however, blink rate periodograms were significant (p less than or equal to 0.003) for only two of the four subjects. Thus, with the qualifications that college students were tested instead of pilots and that they performed monocular laboratory tasks imstead of binocular flight-deck task, it is concluded that 24-h rhythms in accommodation responses need not be considered in setting visual standards for flight-deck task.

Accommodation, Ocular↗
PubMed1975

Vestibular-ocular accommodation reflex in man.

Stimulation of the vestibular system by angular acceleration produces widespread sensory and motor effects. The present study was designed to study a motor effect which has not been reported in the literature, i.e., the influence of rotary acceleration of the body on ocular accommodation. The accommodation of 10 young men was recorded before and after a high-level deceleration to zero velocity following 30 s of rotation. Accommodation was recorded continuously on an infrared optometer for 110 s under two conditions; while the subjects observed a target set at the far point, and while they viewed the same target through a 0.3-mm pinhole. Stimulation by high-level rotary deceleration produced positive accommodation or a pseudomyopia under both conditions, but the positive accommodation was substantially greater and lasted much longer during fixation through the pinhole. It is hypothesized that this increase in accommodation is a result of a vestibular-ocular accommodation reflex.

Accommodation, Ocular↗