摘要:

The Fresnel prism, an outgrowth of the early nineteenth century lenses designed for light-houses by Augustin J. Fresnel, can be imagined as a series of small prisms lying adjacent to each other on a thin transparent platform. Ophthalmic quality Fresnel prisms of almost any power have recently been made of flexible material (less than I mm thick) which can be pressed onto existing prescription lenses. A comparison of membrane Fresnel and conventional prisms is made in terms of designs variables available for each in optimizing prism performance.

ISSN:0002-9408    

出版商:OVID    

年代:1971

数据来源: OVID

摘要:

Degradations of visual performance in vibration environments have been described. The mechanisms involved in the response are poorly understood and limited quantitative data is available. Binocular visual acuity was measured on 28 volunteers at 0.4, 1.0 and 4.0 meters during vibration exposures from 5 to 50 Hz. at ± 0.75 Gz. Viewing distance-dependent variations in acuity suggest that a form of visual tracking may occur at frequencies above 3 Hz provided that the angular displacement is small.

ISSN:0002-9408    

出版商:OVID    

年代:1971

数据来源: OVID

摘要:

When Panum's limits are measured using spectral stimuli, the results do not agree with expectations based upon the known chromatic and prismatic effects of the lens. Instead, the magnitudes of both the near (crossed) and far (uncrossed) limits for single binocular vision show different wavelength dependencies that appear to reflect R-G and Y-B chromatic processes.

ISSN:0002-9408    

出版商:OVID    

年代:1971

数据来源: OVID

摘要:

Previous studies have shown that the fluorescein pattern, which is a contact lens fitter's chief guide in evaluating the contact lens-cornea bearing relationship, is altered by changes in both the contact lens base curve and optic zone diameter. On eight corneas we found the base curve required to maintain an alignment fit for lenses of various optic zone diameters. From the results of this study we can conclude that as the optic zone diameter of a contact lens is increased by 0.5 mm. the base curve must be flattened by 0.25 DK to maintain alignment fitting. This is the Harris-Kubo ratio: ΔBC/ΔOZD = −0.25 DK/0.5 mm.

ISSN:0002-9408    

出版商:OVID    

年代:1971

数据来源: OVID

摘要:

Several methods are used to measure cyclophorias although little is generally done to correct them. It can be shown that what is actually being measured is a rotational disparity between ocular images and that usual methods of measurement fail to distinguish between cyclophorias and oblique meridional aniseikonia, which can also create a rotational disparity. A method of distinguishing the difference between these conditions is described as it may be accomplished in the clinical setting, as well as the diagnostic value of these measurements in the prescribing of spectacles.

ISSN:0002-9408    

出版商:OVID    

年代:1971

数据来源: OVID

摘要:

This paper includes an examination of some of the contradictions encountered in a review of the literature of the title subject. The optics of relative spectacle magnification (RSM) are presented together with the results of calculations which reveal eight basic RSM curves in phakia and aphakia, corrected by a spectacle or contact lens in both refractive and axial errors in the range of 20 D myopia through 20 D hyperopia.Contrary to the literature, there is very little magnification difference between similarly corrected axial and refractive errors within a large range. The basis of the notion of equalizing image size by means of a spectacle-contact lens reverse Colilean telescope is shown to be erroneous. This is demonstrated by an RSM curve drawn from calculated values.

ISSN:0002-9408    

出版商:OVID    

年代:1971

数据来源: OVID

摘要:

The position of physiologic rest of the crystalline lens is the accommodative state which it assumes when all the stimuli to accommodation have been eliminated except the basal innervations.This paper describes a clinical method, devised by the author, which measures this position with considerable precision, and it discusses the physiologic and clinical implications. The test is being used by the author when it is required to evaluate and/or prescribe minus spherical additions for the patient's night driving needs.

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

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