摘要:

Retinal ganglion cells of the goldfish retina show color opponency at photopic levels of illumination. The spectral sensitivity curves fo the opposing excitatory and inhibitory responses indicate two underlying cone mechanisms. At scotopic levels, these same cells show a marked increase in over-all sensitivity and a different spectral sensitivity curve with only one response type. The sign of the scotopic rod response was always the same as that produced by stimulating the long wavelength cone pigment in the center of the receptive field. The change in spectral sensitivity, the large increase in sensitivity, and the clearly demonstrable Purkinje shift in all of the ganglion cells studied indicated that even cells exquisitely tuned to color information have both rod and cone inputs.

ISSN:0002-9408    

出版商:OVID    

年代:1971

数据来源: OVID

摘要:

A fundamental relation between the nature of the corneal surface and the one of the keratoscope rings is found. On that basis three methods to measure the corneal topology are proposed. A comparison between these methods shows that for diffused light we should use a differential equation. On the other hand, to avoid the differentiation, the angle of orientation of the directed light should be known precisely. The precision of these methods vary from 0.02 mm to 0.1 mm according to the methods, the mathematical process and the corneal models which we use.

ISSN:0002-9408    

出版商:OVID    

年代:1971

数据来源: OVID

摘要:

The refraction of the eye may change after wearing contact lenses: these changes are often attributed only to changes in the anterior corneal curvature. However, refractive changes may also be the result of variations in the posterior corneal curvature, corneal thickness and index of refraction as well as a change in the depth of the anterior chamber. The differential calculus permits derivation of equations describing these changes and the results confirmed by computer modification of the basic equation.

ISSN:0002-9408    

出版商:OVID    

年代:1971

数据来源: OVID

摘要:

Numerous investigators since Donders in 1864 have published data on the ocular amplitude of accommodation. In most of these investigators, however, only one set of experimental conditions was used. In this investigation. I used various sets, each of which was presented to 55 males and 55 females from age 13 through age 67. The major results of this investigation were:a) The tables attributed to Donders do not agree with his raw data.b) Subjective grasping of the target stage manifested statistically higher amplitudes than when it was not grasped.c) Movement of the target towards the subject manifested statistically higher amplitudes than when the target was moved away from him.d) Statistically higher amplitudes were manifested for binocularity than monocularity above age 32, but not at younger ages.e) There was no statistical significance between the amplitudes of males and females of the same are group.

ISSN:0002-9408    

出版商:OVID    

年代:1971

数据来源: OVID

摘要:

The modulations transfer theory has been applied to a rigorous investigation of the effect on the retinal image of several types of contact lenses designed to help in presbyopia. Among those investigated are the segmented bifocal, the two-curve bifocal, and pupil restriction. The effect of these various lenses on the extension of the depth of field is illustrated, and it is shown that the restricted pupil lens makes a significant contribution to the depth of field at an acceptable sacrifice in brightness.

ISSN:0002-9408    

出版商:OVID    

年代:1971

数据来源: OVID

摘要:

Almost all ERGs are obtained by using AC amplifiers, because these are more stable. However, the AC amplifier delivers a degraded first derivative of the DC signal at the cornea, resulting in a misrepresentation of both time and amplitude, as well as an entirely artifactual “negative overshoot” which does not exist at all. ERGs amplified by both AC and DC methods are presented for comparison. A new type of DC amplifier has permitted a new and greatly simplified geometric analysis of the ERG.

ISSN:0002-9408    

出版商:OVID    

年代:1971

数据来源: OVID

摘要:

Researchers in optometry can get most use from the computer by writing programs for themselves rather than just presenting their experimental results for statistical analysis. “A computer-orientated” approach can bring fresh light to bear on hitherto insoluble problems and also requires the programmer to learn to analyze his problems in a logical way. Some examples are given of the logical analysis of some typical optometric problems with the aid of flow-charts. Examples of computer programs for solving problems in corneal topography, thick lens systems, chromaticity and patient control are given.

ISSN:0002-9408    

出版商:OVID    

年代:1971

数据来源: OVID

摘要:

Many important factors governing the design and fitting of tiny-thinner single-cut corneal lenses for aphakics are derived and presented here from a five-year personal experience of fitting more than 1,400 aphakic eyes with lenses of this exact type. A center thickness of 0.35 mm or less seems to be the critical factor in fitting of tiny-thinner single-cuts for aphakics. Exact dimensions are presented here of an eight-lens diagnostic trial set which is essential for determining a fit with “maximal bearing surface.” Special edge treatment is essential to aid “self-removal” which is the number one problem with these lenses. “Extreme comfort,” minimal “spectacle blur” and no “limbal encroachment” pathology, are good reason for fitting these tiny-thinner single-cuts for aphakics.

ISSN:0002-9408    

出版商:OVID    

年代:1971

数据来源: OVID

摘要:

A presentation of a simple clinical method of determination of field of view of telescopic low vision lenses. The consideration of field characteristics in selecting and prescribing low vision aids.

ISSN:0002-9408    

出版商:OVID    

年代:1971

数据来源: OVID

ISSN:0002-9408    

出版商:OVID    

年代:1971

数据来源: OVID