My fifty years in ophthalmic standards.

I believe that optometry has gained tremendously from its involvement in the standards process. It enables us to reach out and become involved with other disciplines with which we might not otherwise develop relationships. We learn from the process and from these other disciplines, and what we learn is brought into our professional database through the educational process. It is important that we contribute our knowledge and skills to the development of standards because it is a way in which we can show others what we know and also provide meaningful leadership. I have every reason to believe that our participation in standards will be as satisfying in the future as it has been in the past.

Colors of maximal saturation.

The spectrum locus on the CIE Chromaticity Diagram represents monochromatic stimuli which have been exposed to a dark adapted fovea. Some of these colors can be made to appear more saturated by chromatic adaptation. The colors both inside the spectrum locus and the supersaturated colors outside are bounded by a four-sided boundary line which constitutes the locus of colors of maximal saturation. An attempt has been made to show how this quadrilateral is related to the fundamental colors and to a zone theory of color vision.

Spectral response curves of congenital dichromats.

In a previous paper I have derived spectral response curves for the foveal cones of the CIE normal observer. These are based on the 1931 mixture data, the Judd 1951 V (lambda) curve, and the absorbance data of the pigments in the human cones. In the present paper I have found that the spectral response curves of congenital dichromats may be assumed to be similar to those of the CIE normal observer.

Foveal photopigments.

The relative rates of absorption of quanta per unit of energy for the various wavelengths can be assessed for the human red, green, and blue photoreceptors by assuming that the responses generated by a photoreceptor are proportional to the rate of absorption of quanta. We start by selecting three points on the color mixture diagram to represent the fundamental colors. The mixture diagram is then transformed to a constant luminance diagram in which the fundamental colors serve as primaries. The V(lambda) values are then multiplied by the chromaticity coordinates (r, g, and b) to determine the response curves of red, green, and blue cones. The values of V(lambda)r, V(lambda)g, and V(lambda)b are divided by the transmittance of the ocular media and the wavelength to give the relative absorptions. No allowance has been made for self-screening or population densities. I have used the Judd (V(lambda) curve and the Wright-Guild mixture data. I have found three fundamental colors which yield predictions for the absorption curves of the photopigments of the foveal cones which conform well to the absorbance curves measured directly.

Stiles-Burch two-degree color mixture data.

The 2 degree color mixture data of Stiles and Burch have been analyzed to study the differences between individual subjects and the lack of precision at the blue end of the spectrum. The luminous efficiency data have been compared to those of Judd's 1951 observer and the 1931 standard observer. The mixture data have been compared to those of Wright and Guild and have been related to mixture data of dichromats. One of the ten observers was found to have a luminous efficiency curve similar to that of a protanope and was excluded from the average data.

A model for the visual perception of direction.

An attempt is made to explain how the eyes can be moved with respect to the head and the observer can still assess the direction of an object in space fixed with respect to the head. My explanation is based on the assumption that the subject is made aware of the direction in which the eyes are pointing by the output from the brain center controlling the direction of fixation. He associates this signal with an awareness of "looking in a certain direction." The image falling on a certain point of the retina (usually near the center of the fovea), which I call the anchor point, is perceived as lying in the direction in which he "perceives himself to be looking." The directions of other objects are judged relative to the object that forms its image on the anchor point.

Color mixture data for normals and tritanopes.

In the author's theory of color vision the blue and the green fundamental fall on a tritanopic confusion line. This provides the basis for comparing the mixture data of a tritanope with those of a normal. At the red end of the spectrum the data conform very well to what is predicted by theory. At the blue end the data point to the possibility that the pigment responsible for the red response may differ from the pigment involved at the red end of the spectrum.

Dichromatic confusion lines and color vision models.

An attempt has been made to explain how dichromatic confusion lines can be used in building a model for color vision. In the König color vision model the fundamental colors are located on the mixture diagram at the copunctal points for protanopes, deuteranopes, and tritanopes. In Fry's model the copunctal points fall on the alychne and cannot represent the fundamental colors. On a constant luminance diagram the confusion lines for the different dichromats are sets of parallel lines. This arrangement of the confusion lines can be explained in terms of a zone theory of color vision.

Mixture and luminosity data for dichromats.

The mixture diagram for a dichromat reduces to a single line connecting two points that represent the surviving fundamental colors. The intermediate colors match mixtures of the two fundamentals. The luminous efficiency curve can be split into its red and blue, or red and green, or green and blue components which represent the response curves. These response curves can be compared to the response curves of a normal trichromat. The curves derived for a trichromat depend upon the points chosen to represent the three fundamentals. The rationale involved in the choice of fundamentals is explained. The choice depends on (1) the shape of the spectrum locus, (2) adaptation data, and (3) the directions of the confusion lines for dichromats. The red curve derived for a trichromat in this way has two peaks, one at each end of the spectrum. The peak at the short wave end is missing in the case of deuteranopes. Otherwise, the curves in dichromats and trichromats are similar. No allowance has been made for effects of macular pigment and transmission of the media.

Mixture and luminosity data for anomalous trichromats.

In a previous paper a procedure was outlined for locating the red, green, and blue fundamental colors on a color mixture diagram. This makes it possible to derive the red, green, and blue response curves from the mixture data and the luminous efficiency curve. Curves were derived in a similar way for dichromats and compared to those for normal observers. In this paper, the study has been extended to include anomalous trichromats. In normal observers, tritanopes, and deuteranomalous subjects, the red response curve has two peaks, one at the red end and one at the blue end. The red response can be analyzed into long wave and short wave components. The short wave component is missing in deuteranopes and in the protanomalous observer investigated in this study. The data based on the one protanomal point to the possibility that the long wave component of the red response of the protanomal is similar to that of the normal but reduced in magnitude. In the deuteranomal, the green response is similar to that of a normal but reduced in magnitude.

The Bezold-Brücke phenomena at the two ends of the spectrum.

Purdy's study did not cover the two ends of the spectrum. He stopped at 460 and 650 nm. This study extends the data down to 400 nm at the blue end and up to 680 nm at the red end. The data obtained tie in with a previous study of the purple colors involving mixtures of 460 and 667 nm. We now have a clear picture of what occurs at all parts of the color circle.

Chromatic adaptation and the blue-green side of the color triangle.

This is an attempt to show with chromatic adaptation data that the line tangent to the spectrum locus at about 460 nm and passing through the tritanopic confusion point represents the blue-green leg of the triangle of fundamental colors. The inability to use chromatic adaptation to produce colors in the green corner of the triangle has been explained in terms of a zone theory of color vision.

Pupillary micro movements apparently related to pulse frequency.

Pupillary micro changes in diameter apparently related to pulse frequency are superimposed on the larger fluctuations called the pupillary unrest. This small component of the pupillary unrest waxes and wanes with each pulsation of the blood. The effect was found to vary inversely with the average pupil diameter which can be controlled by making the eye accommodate or allowing more or less light to enter the eye.

The component of physiological pupillary unrest correlated with respiration.

Components within physiological pupillary unrest have been shown to be correlated with respiration. A convolution technique has shown that a component of the unrest can be found to be correlated with respiration as the respiration is voluntarily controlled in rhythm to auditory cues over a range of respiration rates from 0.10 to 1.0 Hz. The components account for only a portion of the unrest, on the order of 0.10 mm of fluctuation in pupil diameter per cycle.

Adaptation and the Ives effect.

The Ives effect is the discrepancy between photometric matches made by direct comparison and those made by flicker. When white is used as a standard stimulus, the discrepancy appears to be related to the saturation of the test stimulus. The two methods of photometry involve differences in adaptation. In flicker, the two patches of color are applied to the same retinal area alternately, and the retina becomes adapted to a mixture of the two. In direct comparison, the two colors are applied to separate areas of the retina, each of which becomes adapted to the color falling on it. In this study the state of adaptation is controlled by reversing the bipartite pattern from right to left from reading to reading so that each part of the retina becomes adapted to a mixture of the two colors the same as in flicker. This reversal decreases the Ives effect to an almost negligible amount, indicating that adaptation is a major cause of the effect. Data are also presented for use of yellow and blue standards instead of white.

Adaptation and heterochromatic matching.

This study is a follow-up of a previous study of the effect of adaptation on heterochromatic matching by flicker photometry and direct comparison. In flicker photometry, two patches of color are applied alternately to a region of the retina adapted to a mixture of the two colors. In direct comparison, the two halves of the pattern are usually applied to regions of the retina adapted to the separate colors. Two additional methods of equalizing the state of adaptation in the two halves of the retina in direct comparison matching have been tested. In both cases, equalizing the states of adaptation reduces the discrepancy between flicker photometry and direct comparison for two of the three subjects tested. For the third subject, the discrepancies are small but one can still demonstrate effects produced by equalizing the states of adaptation. Further study is needed to delineate the specific mechanisms of adaptation involved.

Chromatic adaption and the fundamental stimuli.

A bipartite adaption stimulus with a horizontal dividing line adapted the upper half of the retina to red or yellow light and the lower half to white light. Monochromatic test stimuli between 460 and 520 nm were presented to the red or yellow adapted portion of the retina. After desaturating the test stimulus with red light, it was possible to match it to a mixture of 458 and 520 nm. From these data one can plot on a mixture diagram the shifts in color produced by the two kinds of adaption. The data support a zone theory of color vision similar to that proposed by Adams.

The absence of the Ives effect in a deuteranope.

Ives found that when monochromatic stimuli are matched to white by flicker photometry, they are not equal in brightness to the white by direct comparison, and the discrepancy is minimal for yellow but is increased for longer and shorter wavelengths. On the two sides of yellow, the colors are more saturated, and Ives postulated that brightness involves the sum of a chromatic component and an achromatic component and that the chromatic component varies with the saturation. In the case of a deuteranope, one would expect a vigorous chromatic response for yellow and blue stimuli but a poor response for the neutral part of the spectrum. The Ives effect is virtually nonexistent for subject SR, who is a deuteranope. In terms of the zone theory of color vision, this would mean that the blue-yellow chromatic channel contributes little or nothing to brightness. In a normal observer, the blue-yellow mechanism can be isolated by using blues and yellows depurified with white, but in this case the Ives effect is found to exist.

The Bezold-Brücke phenomenon for purple colors.

A bipartite stimulus 2 degrees in diameter was used to study the Bezold-Brücke phenomenon for purple colors. A mixture of 460 nm and 667 nm in one half at a given luminance was matched with a mixture of the same two wavelengths at a luminance level 10 times higher. The hue of the 667-nm stimulus was not affected by the change in luminance. There is one mixture of red and blue which remains unchanged in hue as the luminance increases. Reddish purples shift toward red and bluish purples toward blue. These findings are consistent with a zone theory of color vision such as proposed by Adams.