Showing papers on "Accommodation published in 1978"
TL;DR: Evidence is presented that the focus of the eye tends to return passively to an individually characteristic intermediate resting position or dark-focus whenever (1) the stimulus to accommodation is degraded or (2) when the quality of the image is independent of focus.
Abstract: Experimental evidence is presented that the focus of the eye tends to return passively to an individually characteristic intermediate resting position or dark-focus whenever (1) the stimulus to accommodation is degraded or (2) when the quality of the image is independent of focus. Based on measurements of the dark-focus with a laser optometer, it is possible to predict the magnitude of night, empty field, and instrument myopia on an individual basis. The role of the intermediate dark-focus as a factor in accommodation also provides an explanation for the paradoxical variation of visual acuity with observation distance. Applications to night myopia and night driving are described, and implications for clinical practice are discussed.
190 citations
TL;DR: The monocular, steady-state response to targets under various colors of illumination is investigated and it is shown that the ocular longitudinal chromatic aberration increases slightly with accommodation.
Abstract: Previous studies of the effects of color on the accommodation response are reviewed. The monocular, steady-state response to targets under various colors of illumination is investigated. It is shown that trained observers change their level of accommodation, when viewing a target at a constant distance, to compensate for the varying ocular longitudinal chromatic aberration as the color of the target is changed. Untrained subjects, however, may initially show inconsistent responses. Results in white and greeen are closely comparable. Dynamic aspects of these effects are illustrated and it is shown that the ocular longitudinal chromatic aberration increases slightly with accommodation. The results are related to current ideas on the accommodative system.
102 citations
TL;DR: A model involving dynamic evaluation of the changes in retinal‐image modulation produced by accommodation fluctuations accounts for many features of the observations.
Abstract: The steady-state, monocular accommodation response to sinusoidal grating targets was assessed as a function of the spatial frequency of the grating and its vergence at the eye, using a laser optometer. At all levels of accommodative stimulus, the response was found to be dependent on grating frequency. At very low frequencies, the response was often substantially in error and was closely related to the accommodation exercised by the observer when viewing an empty field. At higher frequencies, the response became more accurate. Possible models for accommodative strategies underlying the experimental results are discussed. A model involving dynamic evaluation of the changes in retinal-image modulation produced by accommodation fluctuations accounts for many features of the observations.
82 citations
TL;DR: The presence of a new dynamic range nonlinearity in accommodation dynamics is shown, which is slower when the eye is operating in the near range; conversely, relaxation of accommodation is apparently slower during work in the far range.
Abstract: We show the presence of a new nonlinearity in accommodation dynamics. Positive accommodation is slower when the eye is operating in the near range; conversely, relaxation of accommodation is apparently slower during work in the far range. Latency of accommodation is unaffected by working range. This new dynamic range nonlinearity has been defined in connection with a continuing research study of accommodation responses in normal subjects and in clinic patients. Instrumentation and analysis procedures are described.
57 citations
TL;DR: The temporal stability of the dark focus of accommodation (the refractive power of the eye in total darkness) was examined using a laser optometer and it was found that dark focus does not vary greatly in most subjects over a period of 2--3 weeks.
Abstract: The temporal stability of the dark focus of accommodation (the refractive power of the eye in total darkness) was examined using a laser optometer. It was found that dark focus does not vary greatly in most subjects over a period of 2-3 weeks. Intrasubject ranges varied from 0.08-2.92 D over that period, with a mean range of 1.07 D. Theoretical and practical implications of these findings are discussed.
40 citations
TL;DR: Binocular eye movements were recorded photoelectrically while observers looked from one target to a second, located in a different direction and at a different distance, when the two targets were “real” with no accommodation convergence mismatch.
36 citations
TL;DR: Field studies with a fixed-focus sighting telescope support the idea that an observer may be able to compensate partially for the aberrations of a visual instrument, in particular, for field curvature and astigmatism.
Abstract: The possibility is discussed that, through the exercise of his accommodation, an observer may be able to compensate partially for the aberrations of a visual instrument, in particular, for field curvature and astigmatism. The relevant properties of the accommodation response are briefly reviewed. Experiments are described in which an astigmatic image field was simulated with the aid of cylindrical lenses, and the accommodation responses were determined with a laser optometer. Observers were found to adjust their accommodation with the orientation of a grating target in such a way as to attempt to minimize the effects of the instrumental astigmatism. The degree of compensation achieved depended upon the position of the image vergence within the range of accommodation of the observer. Field studies with a fixed-focus sighting telescope support these ideas.
23 citations
01 Nov 1978
TL;DR: In this article, the apparent size of a simulated horizon moon was measured as a function of the distribution of texture in the natural vistas against which it appeared, and it was found that size increased as the distance to the dominant textural stimulus to accommodation increased and decreased as the moon rose above the plane of surface texture.
Abstract: : In two experiments the apparent size of a simulated horizon moon was measured as a function of the distribution of texture in the natural vistas against which it appeared. Size was found to increase as the distance to the dominant textural stimulus to accommodation increased and to decrease as the moon rose above the plane of surface texture. In the second experiment, the subjects' accommodation distances to the various scenes were also measured with a laser optometer, and after appropriate transformations, the size judgments were found to correlate .89 with the measured accommodation values, thereby suggesting that the fabled moon illusion is mediated by the oculomotor adjustments of visual accommodation. (Author)
16 citations
Patent•
13 Sep 1978
TL;DR: An optical system composed of three lens assemblies disposed serially along a common optical axis was proposed in this paper to obtain panoramic views of objects dispersed within the interior of a bank vault, where an observer's eye located behind it can see the final image with an apparent diameter essentially equal to that at which the initial image can be seen at the entry of the second assembly.
Abstract: An optical device insertable through a peephole in the thick wall of a chamber such as a bank vault, making it possible for an observer to obtain a panoramic view of objects dispersed within the interior thereof. The device is constituted by an optical system composed of three lens assemblies disposed serially along a common optical axis. The first assembly has wide angle characteristics to develop in front of this assembly a virtual image of the objects in the interior. The second assembly has an elongation nearly equal to the thickness of the wall, the second assembly having convergent characteristics to derive from the virtual image a final image which is formed adjacent the exit of this assembly. The third assembly has accommodation characteristics to permit an observer's eye located behind it to see the final image with an apparent diameter essentially equal to that at which the initial image can be seen at the entry of the second assembly. As a consequence, an observation of objects through the optical system is essentially equivalent in image quality to that obtainable had the observation of the initial image been made directly with the first and third assemblies.
01 Apr 1978
TL;DR: For example, this article found that the average accommodation distance may be far from the distance of the viewed object, but the more or less rhythmic fluctuations in accommodation distance are enough to bring an out-of-focus object into focus momentarily every so often, at which times it may be sampled by the brain.
Abstract: : Somehow we see things clearly, or at least are unaware that they are unclear, when in fact the images on our retinas are badly out of focus as determined by an infrared optometer. Although the average accommodation distance may be far from the distance of the viewed object, the more or less rhythmic fluctuations in accommodation distance are sufficiently large to bring an out-of-focus object into focus momentarily every so often, at which times it may be sampled by the brain. Furthermore, if objects are brought into focus regardless of accommodation distance by the use of a small artificial pupil, the accommodative mechanism will quickly lapse toward its intermediate resting position and then, after a minute or two for many subjects, will embark upon a series of extreme fluctuations, as if searching for an out-of-focus image to back away from. These and other incidental experimental observations are now subjects of an ongoing systematic investigation. (Author)
Journal Article•
TL;DR: The results suggest that the eye's use of the chromatic aberration interval to spare accommodation, as found in previous studies carried out on adults, is learned by about the fourth year of a child's life.
Abstract: Retinoscopy through colored filters (chromoretinoscopy) was used to determine the portion of the chromatic aberration interval in focus when young children (2 to 6 years of age) fixate at far and near. The results indicate that the children may be divided into three distinct groups. In the youngest group there is haphazard focusing within the chromatic aberration interval at far and near. The middle group shows selective focusing of the red end of the chromatic interval at both far and near. Children in the oldest group focus the red end when fixating at far and the green end when fixating at near, thereby sparing accommodation. These results suggest that the eye's use of the chromatic aberration interval to spare accommodation, as found in previous studies carried out on adults, is learned by about the fourth year of a child's life.
TL;DR: A quantitative physics laboratory exercise, dealing with the optical features of the human eye, and the accommodation effect of the observer’s eye is discussed and the observer examines the refractive power of his own eyes.
Abstract: A quantitative physics laboratory exercise, dealing with the optical features of the human eye, is described. An artificial eye model with approximately the real focal length was constructed. This is used as an object in direct and indirect ophthalmoscopy. The magnification of the retina by the eye lens is measured and (further) a corrective lens for refractive anomaly of the model is determined using both a subjective and an objective method. The accommodation effect of the observer’s eye is discussed and, at the end of the exercise, the observer examines the refractive power of his own eyes. This laboratory experiment has been designed for medical and biology students.
Journal Article•