scholarly journals THE DARK ADAPTATION OF THE HUMAN EYE

1920 ◽  
Vol 2 (5) ◽  
pp. 499-517 ◽  
Author(s):  
Selig Hecht
Keyword(s):  
Dark Adaptation ◽  
Photochemical Reaction ◽  
Quantitative Data ◽  
Dark Reaction ◽  
Human Eye ◽  
Visual Threshold ◽  
Bimolecular Chemical Reaction ◽  
Dim Light ◽  
Visual Reception ◽  
Photosensitive Substance

During the dark adaptation of the human eye, its visual threshold decreases to a small fraction of its original value in the light. An analysis of the quantitative data describing this adaptation shows that it follows the course of a bimolecular chemical reaction. On the basis of these findings it is suggested that visual reception in dim light is conditioned by a reversible photochemical reaction involving a photosensitive substance and its two products of decomposition. Accordingly, dark adaptation depends on the course of the "dark" reaction during which the two products of decomposition reunite to synthesize the original photosensitive substance.

scholarly journals SENSORY EQUILIBRIUM AND DARK ADAPTATION IN MYA ARENARIA

1919 ◽  
Vol 1 (5) ◽  
pp. 545-558 ◽  
Author(s):  
Selig Hecht
Keyword(s):  
Reaction Time ◽  
Latent Period ◽  
Dark Adaptation ◽  
Photochemical Reaction ◽  
Short Interval ◽  
Bimolecular Reaction ◽  
Mya Arenaria ◽  
Rational Explanation ◽  
Order Of Magnitude ◽  
Photosensitive Substance

1. The reaction time of Mya to light is composed of two parts. The first, a sensitization period, is an exceedingly short interval of the order of magnitude associated with photographic processes. The second is a latent period of about 1.3 seconds, during which Mya need not remain exposed to the stimulating light. 2. The process of dark adaptation in Mya is orderly. Its progress may be represented by the formation of a photosensitive substance according to the dynamics of a bimolecular reaction. See PDF for Structure 3. Photosensory equilibrium as represented by the light- and dark-adapted conditions finds a rational explanation in terms of the "stationary state" of a reversible photochemical reaction involving a photosensitive substance and its two precursors. 4. There are two corollaries to this hypothesis. The first requires that the reaction time at sensory equilibrium for a given intensity should vary inversely with the temperature; the second, that the rate of dark adaptation should vary directly with the temperature. Experiments verified both of these requirements.

scholarly journals THE NATURE OF FOVEAL DARK ADAPTATION

1921 ◽  
Vol 4 (2) ◽  
pp. 113-139 ◽  
Author(s):  
Selig Hecht
Keyword(s):  
Stationary State ◽  
Dark Adaptation ◽  
Light Adaptation ◽  
Bimolecular Reaction ◽  
Dark Side ◽  
Light Perception ◽  
Foveal Vision ◽  
Dark Reaction ◽  
Initial Event ◽  
Photosensitive Substance

1. After a discussion of the sources of error involved in the study of dark adaptation, an apparatus and a procedure are described which avoid these errors. The method includes a control of the initial light adaptation, a record of the exact beginning of dark adaptation, and an accurate means of measuring the threshold of the fovea after different intervals in the dark. 2. The results show that dark adaptation of the eye as measured by foveal vision proceeds at a very precipitous rate during the first few seconds, that most of the adaptation takes place during the first 30 seconds, and that the process practically ceases after 10 minutes. These findings explain much of the irregularity of the older data. 3. The changes which correspond to those in the fovea alone are secured by correcting the above results in terms of the movements of the pupil during dark adaptation. 4. On the assumption that the photochemical effect of the light is a linear function of the intensity, it is shown that the dark adaptation of the fovea itself follows the course of a bimolecular reaction. This is interpreted to mean that there are two photolytic products in the fovea; that they are disappearing because they are recombining to form anew the photosensitive substance of the fovea; and that the concentration of these products of photolysis in the sense cell must be increased by a definite fraction in order to produce a visual effect. 5. It is then suggested that the basis of the initial event in foveal light perception is some mechanism that involves a reversible photochemical reaction of which the "dark" reaction is bimolecular. Dark adaptation follows the "dark" reaction; sensory equilibrium is represented by the stationary state; and light adaptation by the shifting of the stationary state to a fresh point of equilibrium toward the "dark" side of the reaction.

scholarly journals Thresholds and noise limitations of colour vision in dim light

2017 ◽  
Vol 372 (1717) ◽  
pp. 20160065 ◽  
Author(s):  
Almut Kelber ◽  
Carola Yovanovich ◽  
Peter Olsson
Keyword(s):  
Shot Noise ◽  
Colour Vision ◽  
Absolute Threshold ◽  
Colour Discrimination ◽  
Dark Noise ◽  
Visual Threshold ◽  
Light Intensities ◽  
Purkinje Shift ◽  
Dim Light ◽  
Receptor Noise

Colour discrimination is based on opponent photoreceptor interactions, and limited by receptor noise. In dim light, photon shot noise impairs colour vision, and in vertebrates, the absolute threshold of colour vision is set by dark noise in cones. Nocturnal insects (e.g. moths and nocturnal bees) and vertebrates lacking rods (geckos) have adaptations to reduce receptor noise and use chromatic vision even in very dim light. In contrast, vertebrates with duplex retinae use colour-blind rod vision when noisy cone signals become unreliable, and their transition from cone- to rod-based vision is marked by the Purkinje shift. Rod–cone interactions have not been shown to improve colour vision in dim light, but may contribute to colour vision in mesopic light intensities. Frogs and toads that have two types of rods use opponent signals from these rods to control phototaxis even at their visual threshold. However, for tasks such as prey or mate choice, their colour discrimination abilities fail at brighter light intensities, similar to other vertebrates, probably limited by the dark noise in cones. This article is part of the themed issue 'Vision in dim light’.

scholarly journals THE PHOTIC SENSITIVITY OF CIONA INTESTINALIS

1918 ◽  
Vol 1 (2) ◽  
pp. 147-166 ◽  
Author(s):  
Selig Hecht
Keyword(s):  
Reaction Time ◽  
Latent Period ◽  
Dark Adaptation ◽  
Local Reaction ◽  
The Body ◽  
Chemical System ◽  
Intensity Analysis ◽  
Constant Ratio ◽  
Neural Mass ◽  
Photosensitive Substance

1. Ciona possesses two means of responding to an increase in the intensity of illumination. One is by means of a local reaction; the other is by a retraction reflex of the body as a whole. 2. The "ocelli" are not photoreceptors. The photosensitive area is in the intersiphonal region containing the neural mass. This area contains no pigment. 3. The reaction time to light is composed of a sensitization period during which Ciona must be exposed to the light, and of a latent period during which it need not be illuminated in order to react to the stimulus received during the sensitization period. 4. The duration of the reaction time varies inversely as the intensity. Analysis shows the latent period to be constant. The relation between the sensitization period and the intensity follows the Bunsen-Roscoe rule. 5. During dark adaptation the reaction time is at first large, then it decreases until a constant minimum is reached. 6. A photochemical system consisting of a reversible reaction is suggested in order to account for the phenomena observed. This system includes a photosensitive substance and its precursor, the dynamics of the reaction following closely the peculiarities of the photosensitivity of Ciona. 7. It is shown that in order to produce a reaction, a constant ratio must be reached between the amount of sensitive substance broken down by the stimulus and the amount previously broken down. 8. From the chemical system suggested certain experimental predictions were made. The actual experiments verified these predictions exactly. 9. The results obtained with regularly repeated stimulation not only fail to show any basis for a learning process or for the presence of a "higher behavior," but follow the requirements of the photochemical system suggested before.

scholarly journals DARK ADAPTATION AND THE LIGHT-GROWTH RESPONSE OF PHYCOMYCES

1929 ◽  
Vol 12 (3) ◽  
pp. 391-400 ◽  
Author(s):  
E. S. Castle
Keyword(s):  
Latent Period ◽  
Dark Adaptation ◽  
Growth Response ◽  
Light Adaptation ◽  
Exposure Period ◽  
Bimolecular Reaction ◽  
Dark Reaction ◽  
Action Time ◽  
Kinetics Of ◽  
Photochemical Action

1. A single-celled, elongating sporangiophore of Phycomyces responds to a sufficient increase in intensity of illumination by a brief increase in growth rate. This is the "light-growth response" of Blaauw. 2. The reaction time is compound, consisting of an exposure period and a latent period (this comprising both the true latent period resulting from photochemical action and any "action time" necessary for the response). During the latter period the plant may be in darkness, responding nevertheless at the end of the latent period. 3. Both light adaptation and dark adaptation occur in the sporangiophore. The kinetics of dark adaptation can be accounted for on the basis of a bimolecular reaction, perhaps modified by autocatalysis. Attention is called to the bimolecular nature of the "dark" reaction in all other photosensory systems that have been studied, in spite of the diversity of the photosensitive substances themselves and of the different forms of the responses to light.

scholarly journals THE REGENERATION OF VISUAL PURPLE IN THE LIVING ANIMAL

1942 ◽  
Vol 26 (1) ◽  
pp. 27-47 ◽  
Author(s):  
James C. Peskin
Keyword(s):  
Vitamin A ◽  
Dark Adaptation ◽  
Light Adaptation ◽  
Living Animal ◽  
First Order ◽  
Visual Threshold ◽  
Isolated Retina ◽  
Lower Temperature ◽  
Initial Delay ◽  
Sigmoid Shape

1. The accumulation of visual purple in the retina after bleaching by light has been studied in the intact eye of the frog. The data show that duration and intensity of light adaptation, which influence the course of human dark adaptation as measured in terms of visual threshold, have a similar influence on the course of visual purple regeneration. 2. At 25°C. frogs which have been light adapted to 1700 millilamberts and then placed in the dark, show an increase in visual purple concentration which begins immediately and continues for 70 minutes until a maximum concentration is attained. The increase, although beginning at once, is slow at first, then proceeds rapidly, and finally slows up towards the end. Frogs which have been adapted to 9500 millilamberts show essentially the same phenomenon except that the initial slow period is strongly delayed so that almost no visual purple is formed in the first 10 minutes. 3. At 15°C. the initial delay in visual purple regeneration occurs following light adaptation to both 1700 and 9500 millilamberts. The delay is about 10 minutes and is slightly longer following the higher light adaptation. 4. The entire course of visual purple accumulation in the dark takes longer at the lower temperature than at the higher. The temperature coefficient for 10°C. is about 1.8. 5. In contrast to the behavior of the isolated retina which has small amounts of vitamin A and large amounts of retinene immediately after exposure to light, the intact eye has large amounts of vitamin A and little retinene after exposure to light for 10 minutes. In the intact eye during dark adaptation, the amount of vitamin A decreases markedly while retinene decreases only slightly in amount. If retinene is formed in the intact eye, the change from retinene to vitamin A must therefore occur rapidly in contrast to the slow change in the isolated retina. 6. The course of visual purple regeneration may be described by the equation for a first order autocatalyzed reaction. This supposes that the regeneration of visual purple is catalyzed by visual purple itself and accounts for the sigmoid shape of the data.

scholarly journals THE COURSE OF ROD DARK ADAPTATION AS INFLUENCED BY THE INTENSITY AND DURATION OF PRE-ADAPTATION TO LIGHT

1941 ◽  
Vol 24 (6) ◽  
pp. 735-751 ◽  
Author(s):  
Charles Haig
Keyword(s):  
Dark Adaptation ◽  
Light Adaptation ◽  
Prolonged Exposure ◽  
Bright Light ◽  
Time Axis ◽  
Reciprocity Law ◽  
Wide Range ◽  
Dim Light ◽  
The Right

An increase in the degree of light adaptation causes a decrease in the slope of the subsequent rod dark adaptation function and a displacement of the function to the right on the time axis. Over a wide range, these changes occur to the same extent whether the increase in the degree of light adaptation is produced by raising the intensity or by prolonging the exposure. Within these limits, the Bunsen-Roscoe reciprocity law applies to the intensity and duration of pre-exposure. Over a still wider range, dark adaptation has the same course following brief exposure to a bright light as it has following prolonged exposure to a dim light, provided the degree of light adaptation is the same in both instances (as indicated by identical initial dark adaptation thresholds).

scholarly journals Monkeys use the rod-dense retinal region rather than the fovea to visually fixate small targets in scotopic vision

2018 ◽  
Author(s):  
Oleg Spivak ◽  
Peter Thier ◽  
Shabtai Barash
Keyword(s):  
Dark Adaptation ◽  
Scotopic Vision ◽  
Photopic Vision ◽  
Dark Background ◽  
Retinal Region ◽  
Dim Light ◽  
Small Targets ◽  
Visual Conditions

AbstractMonkeys appear to visually fixate targets in scotopic conditions. The function fixations fulfill in photopic vision, keeping the target’s image on the fovea, is nullified in scotopic vision, because the fovea, with its cones, is desensitized in dim light. Here we followed the hypothesis that a previously described retinal region, the locus of maximal rod density, functionally replaces the fovea; we found that with dark background, most of the fixations direct the fovea above the target, so that the target’s image appears to fall on the line connecting the fovea with the locus of maximal rod density. There is considerable trial-by-trial variation in the fixation positions along this line. On the whole, the closer the visual conditions are to full scotopic, the higher is this gaze upshift, indicating the closer does the target fall to the locus of maximal rod density. Mesopic background induces low mean upshift. Full (45-min) dark adaptation was essential to achieving high upshift values. There is no analogous photopic effect – 45-min ‘bright adaptation’ did not shift the locus of photopic fixation.

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