摘要:

Fiber optics elements coupled to photosensitive elements are broadly distributed in the animal kingdom. What is their primary (common) role? It is argued that photoreceptors collect energy falling on them and transport it to an oriented photolabile pigment. All fiber optics elements have a limiting aperture and bence, are directionally transmitting and directionally sensitive. For these detector elements to act efficiently, they must be oriented so that they optimally absorb light passing through the center of the source of the relevant visual stimulus or signal—the eye pupil. By that means the fiber optics element aids in limiting stray light “noise.”Laties has demonstrated histologically that vertebrate retinal receptors are oriented towards an anterior point in the eye. This phenomenon is present in eyes with mixed rod-cone populations, as well as in eyes categorized as essentially pure rod or pure cone.This important finding may be independently validated psychophysically by assuming that the peak of the photopic Stiles-Crawford function identifies the central orientational tendency of cones located in the retinal area tested. Predictions may be made for the locus of that peak in the entrance pupil of the eye for various orientational tendencies. By testing the Stiles-Crawford function at a number of different retinal points, orientational properties of human photoreceptors may be defined.The resultant data indicated that the retinal receptors were oriented towards the center of the exit pupil of the eye. This confirmed the findings of Laties. and identified the anterior point “D” towards which the receptors are directed. Thus, the raison d'etre for receptor fiber optics properties is greatly clarified, and a major organizational property of the retina confirmed.The fascinating questions of how that orientation is established and maintained and the effects of disruption in that organization are considered. Added evidence is presented for the establishment of anterior-pointing of retinal receptors prior to birth (hatching).Lastly, a relationship between anterior pointing photoreceptors and associated tapecal back-reflecting plates in the shark eye is demonstrated.

ISSN:0002-9408    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

Glass lenses (with and without vinyl Fresnel optical membranes pressed onto the back surface) were impacted by dropped and ballistically-fired steel balls. High speed cinematography of fracturing showed that regardless of fracture resistance (which was not altered by the membrane), glass fragments were splintered off the back lens surface or were driven through the lens. The membrane either prevented back-surface emission of lens particles or contained the fragments in their travel toward the eye-plane, thereby reducing the danger of ocular injury from broken spectacle lenses.

ISSN:0002-9408    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

When axial anisometropia is corrected by spectacles, retinal image sizes are approximately equal; if contact lenses were to be used, the myopic eye would have the larger retinal image. Clinical tests measuring aniseikonia with spectacle lenses and with contact lenses do not show the aniseikonia to be related to the expected retinal image size, but show that there is less aniseikonia with contact lenses than with spectacle lenses. It is supposed that the reason for this lack of cotrelation is that the more myopic eye is stretched at the posterior pole. Thus a larger retinal image stimulates the comparative number of receptors as a smaller retinal image of a less myopic eye.

ISSN:0002-9408    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

The difficulty in management of the growth of knowledge and meeting societal needs suggests the development of an optometric system of disease detection on a foundation other than differential diagnosis. The structure of such a system may be found in applying the techniques of Decision Analysis to the logical bases for evidence of disease.

ISSN:0002-9408    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

Some basic problems concerning vision test charts, such as size progression and target selection are discussed. It is suggested to use a chart containing on one side different, possibly non-homogeneous, alphabetic letters, on the other side some “gratings” such as the Bessel distributions suggested by Kelly. In this way the classical estimate of visual acuity, complicated by pattern recognition and by multiple discriminations, might be compared to the estimate of the “cut-off” frequency. The difference between these two estimates is expected to depend on the degree of sophistication of the subject. As far as target progression in size is concerned, the use of a constant increment in spatial frequency (say, 3 cpd or 6 cpd) is suggested, according to the linear decay of the transfer function of the visual system. However, this progression does not correspond to the geometrical progression usually recommended.

ISSN:0002-9408    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

The integrated squared autocorrelation function of an image can be shown to represent a measure of pattern information or more commonly a measure of the amount sharpness and complexity of contour and contrast in the image. The autocorrelation function can thus provide a relative measure of image focus inasmuch as contour and contrast information is lost as an image goes out of focus. It is argued that the autocorrelation of the retinal image could be used as a feedback signal for control of visual accommodation and that such a mechanism is consistent with many well known phenomena of accommodation. In addition it is shown that the autocorrelation model can simulate quantitative data obtained from experiments on human accommodative behavior.

ISSN:0002-9408    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

GSR latency, mean amplitude and quiescent or post reading time during and after reading paragraphs of 20/50 acuity level or 1.5 mm letters at four low illumination levels were investigated. The Beckman Dynograph with miniature skin electrodes was used to record the GSR of twelve male college students. Results showed that this range of illumination has no effect on latency or post reading response time but that the curve for amplitude vs. illumination is linear.

ISSN:0002-9408    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

Oxygen consumption rate of corneal epithelium must be known in order to estimate the effect of contact lenses conventional or hydrophilic on corneal metabolism. The in vivo measurements reported here were made with a polarograpbic oxygen sensor on a human eye. The oxygen consumption rate of the human corneal epithelium is estimated to be 2.8 microliters per cm2per hour at 33°C, in good agreement with previous data on rabbit corneal epithelium. The oxygen consumption rate is independent of oxygen tension from 620 mm Hg (80% O2) down to about 20 mm Hg.

ISSN:0002-9408    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

Discontinuing contact lens wear may lead to significant fluctuations in corneal hydration, corneal curvature and refractive error. Only those subjects who showed changes in corneal hydration while wearing their lenses demonstrated corneal fluctuations when lens wear was discontinued. Measurements of corneal thickness and refractive error are good indicators of determining when corneal hydration has stabilized. On those subjects who showed significant fluctuations in curvature refractive error and hydration a new lens was refitted which prevented these fluctuations from occurring when lens wear was discontinued.

ISSN:0002-9408    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

Keratometer measurements were made on 230 unselected Indian children in Northern Saskatchewan and 323 unselected Caucasian children in Kitchener, Ontario. It was found that the Indian children had significantly higher mean corneal astigmatism than the Caucasian children. Comparisons were also made with unselected Indian children in Brantford. Ontario; with unselected California children: with Caucasian and Maori children in New Zealand; with Caucasians in Winnipeg. Manitoba: and with Zuni Indian children in New Mexico. Genetic, cultural and nutritional factors are discussed as possible causes for the differences found.

ISSN:0002-9408    

出版商:OVID    

年代:1972

数据来源: OVID