Rhodopsin measurement and dark‐adaptation in a subject deficient in cone vision

This paper is the third in a succession, of which the first (Rushton, 1961) will be referred to as paper I, the second (Fuortes, Gunkel & Rushton, 1961) as paper II. In paper II we described some studies upon a photanope-a subject whose photopic vision was very defective, but whose rod vision appeared to be normal. In particular, the increment threshold, obtained from a retinal region distant 70 from the fovea, coincided with the results of Aguilar & Stiles (1954), obtained from normal eyes when special precautions were taken to exclude the contribution from the cones. Now a subject with normal rods, but practically no cone responses, might be expected to give very valuable information upon the relation between log. sensitivity during the course of dark-adaptation and the regeneration of rhodopsin. In paper I the course of rhodopsin regeneration was measured in the normal eye, and was found to develop according to a monomolecular reaction with time of half regeneration 4 or 5 min. It was seen, moreover, that after substantial bleaches of various amounts, when rod vision first appeared (at about 2 log. units above the final threshold IO) rhodopsin was always about 90 % regenerated. It was argued that there was a fixed relation between the threshold I and the fraction of opsin still uncombined with retinene-in fact, that this fraction was proportional to log. (I/IO). It was impossible, however, to test this relation experimentally over a range greater than 10% of bleaching, since this already causes the rod threshold to rise to the level of that for the cones, and with further bleaching all vision appears to be cone vision and rod thresholds ascend upon a curve of conjecture somewhere in the space above the horizontal cone branch. But a subject without cones would not in this way conceal the ascending rod curve, and we might hope to follow rod dark-adaptation through a much greater range. This hope has been fulfilled, and we have been able to

[1]  S. Hecht,et al.  THE INFLUENCE OF LIGHT ADAPTATION ON SUBSEQUENT DARK ADAPTATION OF THE EYE , 1937, The Journal of general physiology.

[2]  Charles Frederick Goodeve,et al.  The Effect of Temperature on the Photochemical Bleaching of Visual Purple Solutions , 1938 .

[3]  M. D. Vernon,et al.  THE NATURE OF DARK ADAPTATION , 1941 .

[4]  B. H. Crawford.  Photochemical laws and visual phenomena , 1946, Proceedings of the Royal Society of London. Series B - Biological Sciences.

[5]  B. H. Crawford.  Visual adaptation in relation to brief conditioning stimuli , 1947, Proceedings of the Royal Society of London. Series B - Biological Sciences.

[6]  W. Stiles.  Increment thresholds and the mechanisms of colour vision. , 1949, Documenta ophthalmologica. Advances in ophthalmology.

[7]  L L SLOAN,et al.  The threshold gradients of the rods and the cones; in the dark-adapted and in the partially light-adapted eye. , 1950, American journal of ophthalmology.

[8]  W. Stiles,et al.  Saturation of the Rod Mechanism of the Retina at High Levels of Stimulation , 1954 .

[9]  Dark adaptation to intermediate levels and to complete darkness. , 1954, Journal of the Optical Society of America.

[10]  W. Rushton,et al.  Visual Purple Level and the Course of Dark Adaptation , 1954, Nature.

[11]  R. Weale,et al.  Nervous mechanisms and dark‐adaptation , 1954, The Journal of physiology.

[12]  W A RUSHTON,et al.  The difference spectrum and the photosensitivity of rhodopsin in the living human eye , 1956, The Journal of physiology.

[13]  J. Heck,et al.  Relation of Size of Electroretinogram to Rhodopsin Concentration in Normal Human Beings and one Totally Colour Blind , 1957, Nature.

[14]  H. Barlow,et al.  Change of organization in the receptive fields of the cat's retina during dark adaptation , 1957, The Journal of physiology.

[15]  R. Gunkel,et al.  Automatic intensity control in testing dark adaptation. , 1957, A.M.A. archives of ophthalmology.

[16]  J. Dowling,et al.  THE BIOLOGICAL FUNCTION OF VITAMIN A ACID. , 1960, Proceedings of the National Academy of Sciences of the United States of America.

[17]  W A RUSHTON,et al.  Dark‐adaptation and the regeneration of rhodopsin , 1961, The Journal of physiology.

[18]  R D GUNKEL,et al.  Increment thresholds in a subject deficient in cone vision , 1961, The Journal of physiology.