Gordon L. Walls

The evolutionary history of eye movements

Abstract The nature of eye movements is discussed from the evolutionary point of view. Their origin lies in the need to keep an object fixed on the retina, not in the need to scan the surroundings. Distinctions are made between egocentric and oculocentric directions in their dependence upon voluntary and involuntary eye movements. The possibility, in Man, of retinal correspondency between two regions of the same eye is discussed.

Neutral Points in 138 Protanopes and Deuteranopes

Neutral points have been found by means of a rotary mixer and Munsell papers, minimizing any dispersion of individual values by individual ocular pigmentations. Determined thus, the Illuminant C values for 39 new (post-Walls-Mathews) protanopes covered a range of 3.7 mμ with the mean at 492.3 mμ, those for 38 new deuteranopes a range of 5.8 mμ with the mean at 498.4 mμ.Illuminant D values for 13 additional protanopes covered a range of only 3.3 mμ with the mean at 490.3 mμ, those for 15 recent deuteranopes a range of only 5.1 mμ with the mean at 496.2 mμ. The intergroup gap, observed earlier by Walls and Mathews and also here with “C” values, is clearly genuine so that it is possible to diagnose protanopia and deuteranopia differentially from the neutral-point measurement alone (contrary to universal belief).Evidence is presented that Illuminant D is certainly not “too blue” to be considered a physiological white standard, and that by comparison Illuminant C is really yellowish, so that Illuminant D is the better of the two to use in physiological investigations. This supports the earlier conclusion of Walls and Mathews based on color-normal subjects.

TYPICAL TOTAL COLOR BLINDNESS REINTERPRETED: (Conclusion)

The bipartite dark-adaptation curve is not a >>symptom(( of typical achromasy, in the clinical sense. Still, it demands explanation, by any theory, just as loudly as does any of the characteristics already known a century ago. Sloan’s i 1954) impressive roundup of cases will convince anyone that the ,)kinked<( curve is a regular (though not unvarying) feature of the disease. It is not a freakish finding, as niight be thought if Lewis and Mandelbaum’s (1943) affected sibship still stood alone in the experimental literature. The original pure-rod theory was unable to cope with the demonstration that a majority of cases exhibit an Arago phenenienon. The original day-rod theory was, as we have noted, iion Kries’s way out. The idea of day rods ne>er had strong appeal, and became so well forgotten that in 1838 Hecht wrote as if he thought that it was new with himself. Later writers have credited it to Hecht! The day-rod theory took on its greatest importance when Lezuis and Mandelbaum, and later Sloan, reported finding a bipartite dark-adaptation curve in a great majority of cases. Lewis and Mandelbaum obtained such curves in three of their four cases. Sloan has found the kink in peripheral curves from eleven out of fourteen subjects, and although one of these eleven (S. J . ) probably had no kink a t the fovea, one of the other three ( M . McC), who had shown no kink a t 6 O , probahly did have one a t the fovea. Sloan (1954) attributes the pre-kink portions of her curves