ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

ABSTRACTNormal values for asymmetric prism bar vergences were derived from the clinic population of the School of Optometry, University of Alabama in Birmingham. The means, standard deviations, effect of order of prism presentation, and eye dominancy were examined for three clinical groups. The results provide standards for prism bar vergence and demonstrate that order of testing and dominancy have no significant effect upon the values obtained.

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

ABSTRACTCentral corneal thickness of four human subjects was monitored by optical pachometry during wear of selected hydrophilic (polymacon) contact lenses of known parameters. Simple algebraic techniques were used to calculate anterior corneal surface oxygen flux using central corneal thickness change as an indication of tear layer oxygen tension.

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

ABSTRACTAn experiment was designed that demonstrates that in a state of normal binocular vision a low plus sphere fogging the vision to 6/12 (20/40) produces an inhibition of the central foveal cones in the fogged eye. This inhibition is a natural process that can be switched on and off rapidly so that the fovea receiving the clearer image can examine it and hence produce maximum binocular acuity.

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

ABSTRACTThe initial stages of light and dark adaptation in the human visual system cannot be explained by a simple relation between sensitivity and pigment bleaching. We found changes in sensitivity in the goldfish ganglion cells similar to those seen in humans, and our results from experiments suggest that a change in gain, rather than an overloading of the ganglion cell activity, is responsible for the sensitivity loss. Furthermore, long wavelength background lights selected to stimulate only the long wavelength receptor mechanism produce only the early sensitivity changes in the medium wavelength cone mechanism being monitored at the ganglion cell. This suggests that the early gain changes occur due to neural interaction where different receptor signals merge.

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

ABSTRACTAn equation to determine the weight of a spherical lens as a function of its density, shape, and power is presented. I found that if center thickness and size are held constant, lens weight increases as the lens power increases in minus or decreases in plus. A way to calculate the power at which two lenses are equal in weight when they differ only in density is also presented. This power is the endpoint of a range of powers above which one of the two lenses is heavier, whereas below this power it is lighter than the other lens. A way to reduce the weight of a lens by altering the surface powers is also suggested.

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

ABSTRACTA control theory model that treats the accommodative system and the vergence system each as negative feedback systems is investigated. The effects of accommodative vergence and vergence accommodation are included. The controllers in this model are assumed to be linear time-invariant operators. Only time-independent stimuli are considered. If vergence accommodation is neglected, the model is consistent with classical graphical analysis. By including vergence accommodation, several important changes occur. Disparity vergence is not, in general, equal to the dissociated phoria. The shape of the zone of single, clear, binocular vision is changed. Instabilities in the system arise.

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

ABSTRACTCorneal toricity was measured using a keratometer with the lids in the normal position, and with the lids retracted. Lid retraction usually changed the measured toricity. In corneas with more than 1.00 D of with-the-rule astigmatism, the change was in the direction of less with-the-rule astigmatism. In corneas with astigmatism between 1 D with-the-rule and 1 D against-the-rule, the change was not systematic. The results compare with the original experiment of Masci (1965), who also found that corneas with more with-the-rule toricity show a greater reduction in toricity when the lids are retracted. Clearly the pressure the lids exert on the eyeball is a major factor influencing astigmatism.

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

ABSTRACTArterioles of the human retinal circulation are directly visible and exhibit wide variations in their course. Not only is there marked variation in arteriolar tortuosity within a given age group, but also it has been proposed that the degree of arteriolar tortuosity is different in younger and older age groups. This paper reports on the development of a computer-assisted technique for measurement of arteriolar tortuosity and on the frequency distribution of this index in younger (mean age 22 years) and older (mean age 54.3 years) populations without hypertension.

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

ABSTRACTThis study examines the validity of labeled parameters of aphakia-correcting soft contact lenses. The Nikon Projection Lensometer (NPL) and the Hydro-Vue Soft Lens Analyzer (HSLA) were used by two independent inspectors to measure 51 aphakia-correcting lenses. The contact lens power, diameter, and base curve were measured by each of the inspectors and compared to the labeled parameters. All parameter relations that were analyzed revealed that measurements made by the inspectors were not statistically different (p > 0.05) from each other and that their combined measurements were not statistically different (p > 0.05) from the labeled values.

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID