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Distribution of cones and rods on and near the horizontal meridian. (From G. Østerberg, 1935.)
Relation between wave-length and relative energy required to produce a specific visual effect at high and at low illuminations, respectively. The lower data (rods) are from Hecht and Williams (1922) and represent the relative energy necessary to produce a barely perceptible brightness after prolonged dark adaptation. The upper data (cones) are from Hyde, Forsythe, and Cady (1918) and give the relative energy required to produce a given high brightness, using the fovea (cones) only. The two curves are drawn accurately; the vertical separation has been arranged so that they are nearly coincident at the red end of the spectrum.
Dark adaptation of the fovea as measured with red light. Each point is the average of thirty measurements with fifteen subjects. Intensities are in micromillilamberts. (From Hecht, 1921.)
Dark adaptation of the eye as a whole. Measurements of Engelmann’s eye made by Piper (1903). Note the initial stage of cone adaptation followed by rod adaptation.
The relative ranges of intensity of illumination concerned with cone (high brightness levels) and rod (low brightness levels) vision, respectively. The transition between cone and rod vision is shown as though it occurred suddenly at 0.01 millilambert. The transition actually takes place more gradually in the range of 0.1 to 0.01 millilambert.
Curves of dark adaptation obtained with an area 1 degree in diameter, situated 5 degrees above the fovea. Red1 is the only color which limits the measurements to cones. The other two red filters let through more orange and yellow radiation and hence demonstrate rod adaptation. Cone adaptation is barely perceptible with blue light. (From Kohlrausch, 1922 and 1931.)
The curves of dark adaptation as measured with violet light subsequent to different degrees of light adaptation. These curves show that there is evidence of cone adaptation, as measured with violet light, if the intensity of light adaptation is sufficiently high. The filled-in symbols indicate that a violet color was apparent at the threshold, while the unfilled symbols indicate that the threshold was colorless. (From Hecht and Haig, 1936.)
Dark adaptation of the eye after preadaptation to 3000 luxes for one, two, five, ten, twenty, and forty minutes, respectively. The time axis is the same for all curves; the ordinates are applicable only to the lowest curve; each curve is displaced 0.5 log unit above the preceding curve. The inset at the right hand brings the data together and shows that the longer the preadaptation period (a) the more evident is the dark adaptation of the cones and (b) the more delayed is the secondary rod adaptation. (From Müller, 1931.)
Curves of dark adaptation for the cones and rods for centrally fixated areas whose diameters (in degrees) are shown in the diagram. The larger the field, the sooner does the secondary rod response appear and the greater is the range of intensities covered. (From Hecht, Haig, and Wald, 1935.)
Dark adaptation as measured with a 2-degree retinal stimulus area placed at 2.5, 5, and 10 degrees from the center (0 degrees). Comparison of these data should be made with the data in Fig. 9 for centrally fixated fields of different size. It is to be noted that the farther in the periphery the measurements are made, the sooner does the rod adaptation appear and the lower is the final threshold. (From Hecht, Haig, and Wald, 1935.)
Dark adaptation in fields fixated 15 degrees above the fovea. The thresholds for the 5-degree field are in millilamberts. The remaining curves have been displaced uniformly on the “log threshold” axis to emphasize the identity of form. (From Wald, 1938.)
Graphic analysis of the threshold-area relationship, 25 degrees above the fovea. The open circles were calculated from the averaged data of Table I as discussed in the text. The distribution curves conform to the equation 0.54 log (
Curve illustrating the two portions of dark adaptation; one portion rapid (cones), the other (rods) slower in recovery. The black dots (●) and crosses (×) represent data obtained under similar conditions, time of test and ingestion of food on two different occasions. (From Steffens, Bair, and Sheard, 1940.)
The course of dark adaptation in a group of subjects. The upper and lower curves are of the two persons who yielded the highest and lowest final rod thresholds, respectively, of the group of 110 persons tested. The filled-in circles (●) represent colored response and the open circles (○) indicate colorless light vision. The stippled area contains 80 percent of those tested. (From Hecht and Mandelbaum, 1939.)
Diagrammatic sketch of optical bench and accessories which serve as a satisfactory dark adaptometer. (From Steffens, Bair, and Sheard, 1940.)
Distribution of dark adaptation levels of a group of air pilots. The area between curves 2 and 3 includes 75 to 80 percent of all the readings obtained on the group (Sheard).
Distribution and mean of dark adaptation levels of a group of young school children after a preadaptation exposure for three minutes to a field brightness of 1500 millilamberts (Sheard).
Dark adaptation following four minutes’ exposure to approximately 3000 millilamberts. Open circles: data of monocular test displaced 1 log unit upward. Solid circles: data of four binocular tests on different days. Field 2 degrees in diameter, centered 6 degrees below the fixation point, one-fiftieth second test flashes. (From Wald, 1941.)
Distribution of cone threshold, rod threshold, and cone-rod transition time. The stippled areas represent the female portion of the population tested. (From Hecht and Mandelbaum, 1939.)
Distribution of dark adaptation characteristics according to age. The cone threshold is most affected by age, the rod threshold only slightly, and the cone-rod transition time not at all. (From Hecht and Mandelbaum, 1939.)
Relation between final rod threshold and final cone threshold in a group of twenty-four persons. There is a general tendency for the two thresholds to vary in the same direction (Sheard).
Surveys of the threshold levels from the fovea to a region 40° above the macula using fields of
Dark adaptation after short exposures to various intensities. The initial portions of rod dark adaptation increase in velocity as the light adapting intensity falls. (From Wald and Clark, 1937.)
Dark adaptation after various lengths of exposure to 333 millilamberts. As light adaptation proceeds, the visual threshold rises and independently the speed of rod dark adaptation decreases. (From Wald and Clark, 1937.)
Curves showing the effects of the breathing of oxygen and of the ingestion of a carbohydrate meal on a subject who evidenced fatigue. (From Sheard, Brown, and Wilson.)
Curves 1 and 2 are the course of dark adaptation for the rods and the cones, respectively, in a condition of achromatopsia. Curves 3 and 4 give the corresponding data in the case of an eye of normal acuity and adaptation. (From Sheard and Bair.)
Curves showing the levels of cone and rod adaptation with various sizes of field (R.S.A.) in a case of achromatopsia. (From Sheard and Bair.)
Dark adaptation curves made at various periods during a diet deficient in vitamin A. (From Hecht and Mandelbaum, 1938.)
Final rod and cone thresholds of two subjects on a vitamin A controlled diet. The diagonally shaded part represents a normal diet; the clear part represents a vitamin-free (practically) diet, while the blackened part indicates a normal diet with 50,000 units of vitamin A daily. (From Hecht and Mandelbaum, 1938.)
Thresholds of completely dark-adapted cones and rods (cone and rod “plateaus”) during thirty days of optimal vitamin A nutrition (left portion) and during thirty days on a diet deficient in vitamin A (right portion). Open and closed circles show the thresholds of the right and left eyes, respectively. On the thirtieth day of deficient diet, vitamin A was administered: the course of the curve is shown in Fig. 31,
Relief of hemeralopia by administration of vitamin A and carotene. Measurements preceding administration show terminal portions of dark adaptation. In each section of the illustration, a broken line indicates the average threshold of the normal dark-adapted eye. (From Wald, Jeghers, and Arminio, 1938.)
Composite curves of the courses of dark adaptation for the macula (curves 1, 2, and 3) and for an area (
Curves showing the course of dark adaptation in a subject who was poorly nourished and who had been placed on a restricted diet for many months. The areas investigated were the macula and 10 degrees above the macula, using a
The course of dark adaptation 10 degrees above the macula in a case in which the condition was diagnosed clinically and histologically as pityriasis rubra pilaris, on different days after treatment. Curve 1 was obtained on the day on which treatment was instituted. Curves 2, 3, and 4 represent the courses of dark adaptation which were obtained on the third, eighth, and thirteenth (also on the forty-first) days of continuous treatment. Curve 4 closely approximates the threshold values of a normal subject. (From Brunsting and Sheard, 1941.)
Changes in the dark adaptation curves and thresholds of four subjects suffering from cirrhosis of the liver during the administration of vitamin A. The upper curves from cases
Final rod thresholds of five subjects who were given 20 ml of alcohol and of a control subject without alcohol. (From Yudkin, 1941.)
Final rod thresholds of four subjects to whom were administered 10 mg of benzedrine and of a control subject. (From Yudkin, 1941.)
Dark adaptation curves before and subsequent to the administration of vitamin A to a subject suffering from A avitaminosis. (From Yudkin, 1941.)
The effects of insulin, oxygen, and glucose on light intensity. When the concentration of sugar in the blood was lowered by insulin the thresholds increased. (From McFarland and Forbes, 1940.)
Alterations of dark adaptation under reduced oxygen tensions. As the oxygen tension is diminished the entire curve is displaced upward, indicating impaired sensitivity. The inhalation of oxygen at 15,100 feet (4600 meters) produced a rapid return to normal levels. (From McFarland and Evans, 1939.)
Dark adaptation thresholds at an altitude of 5000 feet (1500 meters) above ground (6000 feet [1800 meters] above sea level) with and without the use of oxygen. (From Sheard, Brown, and Wilson.)
Dark adaptation thresholds at an equivalent altitude of 18,000 feet (5500 meters), showing the marked advantage of oxygen as compared with air. A threefold to fourfold improvement of levels is demonstrated when oxygen is used. (From Sheard, Brown, and Wilson.)
Mean dark adaptation curves showing that, if the oxygen tension was low, the thresholds were high. (From McFarland and Forbes, 1940.)
The effects of anoxia and of glucose on the average dark adaptation curve for four subjects. The solid circles (control curve) are based on measurements obtained in normal air, and the open circles in concentrations of oxygen averaging 10.4 percent. The extent to which glucose counteracted the effects of anoxia on each subject is shown in the difference between the numbered lines at the end of the graph. Each number represents an individual subject. (From McFarland and Forbes, 1940.)
The combined effects of insulin and low oxygen on light sensitivity. The control curve contains measurements in normal air; the open circles indicate data obtained in reduced oxygen and after the injection of 4 units of insulin. These effects were largely counteracted by the ingestion of glucose (indicated readings are triangles), the oxygen tension remaining at its previous level, 13.2 percent. (From McFarland and Forbes, 1940.)
Table III Dark adaptation in total color blindness and in macular degeneration. Values of the logarithms of the threshold levels (micromillilamberts) after various periods of dark adaptation. Retinal stimulus area
Table IV Dark adaptation in follicular hyperkeratosis. Values of the logarithm of the threshold levels (micromillilamberts) after various periods (minutes) of dark adaptation on days subsequent to treatment. Retinal stimulus area=
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