摘要:

This paper reports a technique for comparing the human visual responses with lightness predictions made by a mathematical model. The human visual responses are determined by having a number of observers compare the lightnesses in a Test Display with those in a Standard Display. The mathematical model's predictions are made by processing numbers that are identical to the luminances in the Test Display. These predictions are then scaled relative to the same Standard Lightness Display used by human observers. Methods of analyzing the results are discussed, as well as a variety of situations that can be used to establish whether a particular model can be considered a general model for lightness.

ISSN:0002-9408    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

A model for the structure of the visual pigment rhodopsin is presented. Part of the opsin portion of rhodopsin is assumed as being in the form of an α-helix. The retinene-derived portion of rhodopsin spans at least two turns of the α-helical portion of opsin forming a “retinene opsin” loop. The photoisomerization of the retinene portion causes a change in the loop and produces a strained system. A relief-of-strain process is described in which a proton binding group, attached to opsin, is shown to migrate down the retinene chain producing various semi-carbonium ions via a “semi-protonation process. This model accounts for most of the presently known photochemical phenomena associated with rhodopsin bleaching and predicts several new, as yet undiscovered, intermediates, and where in the bleaching sequence these intermediates will be found. A possible scheme for rhodopsin regeneration is presented.

ISSN:0002-9408    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

The hypothesis tested is that the texture characteristics of targets intermittently exposed below fusion frequency influence brightness. The data are interpreted in relation to the concept of “cortical excitability cycles” as proposed by Bartley.

ISSN:0002-9408    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

An unusual concept in the teaching of elementary geometric optics has been developed, based on a comprehensive system of carefully prepared, closely integrated visual teaching aids. The basis of the system is a building up in overlays of the individual figure which retains the precision usually associated only with conventional single-layer illustration.Before presenting the figure to the students, the instructor breaks the figure down into meaningful fragments and then constructs the figure in class by introducing its concepts in a sequence of overlays. The materials are uniform in their style, execution, and orientation, to allow interchangeability without confusion.

ISSN:0002-9408    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

The visual performance of 40 patients showing myopia of – 15.00 D or more (spherical equivalent) in one or both eyes has been investigated. The increase in visual acuity with corneal lenses exceeds the theoretical expectations considerably. A hypothesis which could explain these findings assumes that the improvement of visual performance is functional and involves certain metabolic pathways and coupling mechanisms. The occurrence of astigmatism and anisometropia had been studied, but not correlation could be found. The failure rate reported in this study refers to unsatisfactory visual performance with corneal lenses and shows an increase with increasing myopia and age.

ISSN:0002-9408    

出版商:OVID    

年代:1970

数据来源: OVID

ISSN:0002-9408    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

Various changes in central corneal curvature have been reported. One possible reason for these apparent changes is diurnal variation. After testing the ability of the average clinician accurately and repeatedly to make keratometric readings, we sought to determine if diurnal variation of the corneal curvature does occur. We found that the cornea changed from its flattest curvature in the early morning to its steepest curvature in the early evening.

ISSN:0002-9408    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

Modern direct ophthalmoscopes offer a broad selection of filters, apertures and focal powers. Their use, with the increase in available illumination, permits the informed examine to make a more definitive examination of the ocular fundus and intervening media. When a first examination of a patient is made and recorded in detail, it affords a base line from which early pathological or other change has increased probability of being detected. A form for organization of such an examination using the instrument's full resources concludes the discussion.

ISSN:0002-9408    

出版商:OVID    

年代:1970

数据来源: OVID

ISSN:0002-9408    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

A department devoted to announcements, reports, appointments, organization data, news, professional problems and ideals, as these relate to the Academy.

ISSN:0002-9408    

出版商:OVID    

年代:1970

数据来源: OVID