scholarly journals Time-course of adaptations for electroretinography and pupillography

2021 ◽  
Vol 9 (4) ◽  
Author(s):  
Ken Asakawa
Keyword(s):  
Dark Adaptation ◽  
Time Course ◽  
Light Adaptation ◽  
Light Condition ◽  
Pupillary Response ◽  
Implicit Time ◽  
Scotopic Vision ◽  
Adaptation Time ◽  
Practical Applications ◽  
Rod Response

Cones are primarily involved in photopic vision and light adaptation. Rods are responsible for scotopic vision and dark adaptation. The typical time-courses of light and dark adaptations have been known for century. However, information regarding the minimal adaptation time for electroretinography (ERG) and pupillography would be helpful for practical applications and clinical efficiency. Therefore, we investigated the relationship between adaptation time and the parameters of ERG and pupillography. Forty-six eyes of 23 healthy women (mean age, 21.7 years) were enrolled. ERG and pupillography were tested for right and left eyes, respectively. ERG with a skin electrode was used to determine amplitude (µV) and implicit time (msec) by the records of rod-, flash-, cone-, and flicker-responses with white light (0.01–30 cd·s/m2). Infrared pupillography was used to record the pupillary response to 1-sec stimulation of red light (100 cd/m2). Cone- and flicker- (rod-, flash-, and pupil) responses were recorded after light (dark) adaptation at 1, 5, 10, 15, and 20 min. Amplitude was significantly different between 1 min and ≥5 or ≥10 min after adaptation in b-wave of cone- or rod-response, respectively. Implicit time differed significantly between 1 min and ≥5 min after adaptation with b-wave of cone- and rod-response. There were significant differences between 1 min and ≥10 or ≥5 min after dark adaptation in parameter of minimum pupil diameter or constriction rate, respectively. Consequently, light-adapted ERGs can be recorded, even in 5 min of light adaptation time without special light condition, whereas dark-adapted ERGs and pupillary response results can be obtained in 10 min or longer of dark adaptation time in complete darkness.

The Effect of Changed Extracellular Calcium and Sodium Concentration on the Electroretinogram of the Crayfish Retina

1980 ◽  
Vol 35 (3-4) ◽  
pp. 308-318 ◽  
Author(s):  
H. Stieve ◽  
I. Claßen-Linke
Keyword(s):  
Dark Adaptation ◽  
Time Course ◽  
Calcium Concentration ◽  
Light Adaptation ◽  
Sodium Concentration ◽  
Strong Increase ◽  
Calcium Stores ◽  
Half Time ◽  
Astacus Leptodactylus ◽  
External Calcium

Abstract The electroretinogram (ERG) of the isolated retina of the crayfish Astacus leptodactylus evoked by strong 10 ms light flashes at constant 5 min intervals was measured while the retina was continuously superfused with various salines which differed in Ca2+ -and Na+ -concentrations. The osmotic pressure of test- and reference-saline was adjusted to be identical by adding sucrose. Results: 1. Upon raising the calcium-concentration of the superfusate in the range of 20-150 mmol/l (constant Na+ -concentration: 208 mmol/l) the peak amplitude hmax and the half time of decay t2 of the ERG both decrease gradually up to about 50% in respect to the corresponding value in reference saline. 2. The recovery of the ERG due to dark adaptation following the “weakly light adapted state” is greatly diminished in high external [Ca2+]ex. 3. Lowering the external calcium-concentration (10 →1 mmol/l) causes a small increase in hmax and a strong increase of the half time of decay t2 (about 180%). Upon lowering the calcium concentration of the superfusate to about 1 nmol/l by 1 mmol/l of the calcium buffer EDTA, a slowly augmenting diminution of the ERG height hm SLX occurs. How­ever, a strong retardation of the falling phase of the ERG characterized by an increase in t2 occurs quickly. Even after 90 min stay in the low calcium saline the retina is still not inexcitable; hmax is 5 - 10% of the reference value. The diminution of hmax occurs about six-fold faster when the buffer concentration is raised to 10 mmol/l EDTA. 4. Additional lowering of the Na+ -concentration (208 →20.8 mmol/l) in a superfusate with a calcium concentration raised to 150 mmol/l causes a strong reduction of the ERG amplitude hmax to about 10%. 5. In a superfusate containing 1 nmol/l calcium such lowering of the sodium concentration (208 → 20.8 mmol/l) causes a diminution of the ERG height to about 40% and the shape of the ERG to become polyphasic; at least two maxima with different time to peak values are observed. Interpretation: 1. The similarity of effects, namely raising external calcium concentration and light adaptation on the one hand and lowering external calcium and dark adaptation on the other hand may indicate that the external calcium is acting on the adaptation mechanism of the photoreceptor cells, presumably by influencing the intracellular [Ca2+]. 2. The great tolerance of the retina against Ca2+ -deficiency in the superfusate might be effected by calcium stores in the retina which need high Ca2+ -buffer concentrations in the superfusate to become exhausted. 3. In contrast to the Limulus ventral nerve photoreceptor there does not seem to be an antagonis­ tic effect of sodium and calcium in the crayfish retina on the control of the light channels. 4. The crayfish receptor potential seems to be composed of at least two different processes. Lowering calcium-and lowering external sodium-concentration both diminish the height and change the time course of the two components to a different degree. This could be caused by in­ fluencing the state of adaptation and thereby making the two maxima separately visible.

Changes of Acuity during Light and Dark Adaptation in the Dragonfly Compound Eye

1990 ◽  
Vol 45 (1-2) ◽  
pp. 137-142 ◽  
Author(s):  
Eric J. Warrant ◽  
Robert B. Pinter
Keyword(s):  
Dark Adaptation ◽  
Time Course ◽  
Light Adaptation ◽  
Compound Eye ◽  
Sensitivity Function ◽  
The State ◽  
Intracellular Recordings ◽  
Acceptance Angle ◽  
Angular Sensitivity ◽  
Rapid Reduction

Abstract Intracellular recordings of angular sensitivity from the photoreceptors of Aeschnid dragonflies (Hemianax papuensis and Aeschna brevistyla) are used to determine the magnitude and time course of acuity changes following alterations of the state of light or dark adaptation. Acuity is defined on the basis of the acceptance angle, Δρ (the half-width of the angular-sensitivity function). The maximally light-adapted value of Δρ is half the dark-adapted value, indicating greater acuity during light adaptation. Following a change from light to dark adaptation, Δρ increases slowly, requiring at least 3 min to reach its dark-adapted value. In contrast, the reverse change (dark to light) induces a rapid reduction of Δρ , and at maximal adapting luminances, this reduction takes place in less than 10 sec.

scholarly journals Light and dark adaptation in Phycomyces phototropism.

1984 ◽  
Vol 84 (1) ◽  
pp. 101-118 ◽  
Author(s):  
P Galland ◽  
V E Russo
Keyword(s):  
Dark Adaptation ◽  
Time Course ◽  
Growth Response ◽  
Light Adaptation ◽  
Abnormal Behavior ◽  
Adaptation Level ◽  
Intensity Level ◽  
Wild Type ◽  
Adaptation Mechanism ◽  
Intensity Range

Light and dark adaptation of the phototropism of Phycomyces sporangiophores were analyzed in the intensity range of 10(-7)-6 W X m-2. The experiments were designed to test the validity of the Delbrück-Reichardt model of adaptation (Delbrück, M., and W. Reichardt, 1956, Cellular Mechanisms in Differentiation and Growth, 3-44), and the kinetics were measured by the phototropic delay method. We found that their model describes adequately only changes of the adaptation level after small, relatively short intensity changes. For dark adaptation, we found a biphasic decay with two time constants of b1 = 1-2 min and b2 = 6.5-10 min. The model fails for light adaptation, in which the level of adaptation can overshoot the actual intensity level before it relaxes to the new intensity. The light adaptation kinetics depend critically on the height of the applied pulse as well as the intensity range. Both these features are incompatible with the Delbrück-Reichardt model and indicate that light and dark adaptation are regulated by different mechanisms. The comparison of the dark adaptation kinetics with the time course of the dark growth response shows that Phycomyces has two adaptation mechanisms: an input adaptation, which operates for the range adjustment, and an output adaptation, which directly modulates the growth response. The analysis of four different types of behavioral mutants permitted a partial genetic dissection of the adaptation mechanism. The hypertropic strain L82 and mutants with defects in the madA gene have qualitatively the same adaptation behavior as the wild type; however, the adaptation constants are altered in these strains. Mutation of the madB gene leads to loss of the fast component of the dark adaptation kinetics and to overshooting of the light adaptation under conditions where the wild type does not overshoot. Another mutant with a defect in the madC gene shows abnormal behavior after steps up in light intensity. Since the madB and madC mutants have been associated with the receptor pigment, we infer that at least part of the adaptation process is mediated by the receptor pigment.

scholarly journals Simulating Human Visual Perception in Tunnel Portals

2021 ◽  
Vol 13 (7) ◽  
pp. 3741
Author(s):  
Changjiang Liu ◽  
Qiuping Wang
Keyword(s):  
Experimental Data ◽  
Visual Perception ◽  
Dark Adaptation ◽  
Light Adaptation ◽  
Human Vision ◽  
Adaptation Process ◽  
Human Visual Perception ◽  
Recognition Time ◽  
Design Data ◽  
Adaptation Time

To study the characteristics of light and dark adaptation in tunnel portals, and to determine the influencing factors in light–dark vision adaptation, basic tunnel lighting and linear design data were obtained. In this study, we used a light-shielded tent to simulate the dark environment of a tunnel, observe the driver recognition time for target objects during the light–dark adaptation process, and analyze the light–dark adaptation time of human vision. Based on the experimental data, we examined the relationships between age, gender, illuminance, and light and dark adaptation times, and established a model for these relationships. The experimental results show that the dark adaptation time is generally longer than the light adaptation time. The dark adaptation time is positively related to age and exhibits a cubic relationship. There is no significant correlation between the light adaptation time and age, but the overall trend is for the light adaptation time to gradually increase with increasing age. There is no correlation between gender and light and dark adaptation times, but there is a notable correlation between light and dark adaptation times and illuminance. When the illuminance ranges from 11,000 to 13,000 lux, the light and dark adaptation times are the longest.

scholarly journals Preferred E-mirror luminance levels for diverse ambient light conditions

2019 ◽  
Vol 63 (1) ◽  
pp. 2255-2255
Author(s):  
Seonghyeok Park ◽  
Kitae Hwang ◽  
Sohyun Yoon ◽  
Gyouhyung Kyung
Keyword(s):  
Dark Adaptation ◽  
Light Adaptation ◽  
Light Condition ◽  
Adaptation Period ◽  
Ambient Light ◽  
Light Conditions ◽  
Tablet Pcs ◽  
Ambient Light Condition ◽  
The Mean ◽  
Nighttime Driving

E-mirrors comprised of cameras and visual displays are expected to replace current side mirrors. Although previous studies have extensively examined the effects of E-mirror size and location on drivers’ performance, safety, and preference, little is known about the required E-mirror luminance levels for diverse ambient light conditions that are typically involved in driving. This study examined the effects of ambient light conditions on the preferred E-mirror luminance levels. Sixteen individuals with a mean (SD) age of 25.7 (5.8) years participated in this study. All participants were recruited from a university student population and had more than two years of driving experience. All participants reported no color deficiency. A local institutional review board approved this study. This study considered four levels of ambient light conditions, two levels of eye adaptation (light and dark), and two levels of eye adaptation phase (initial and final). The four illuminance levels simulated daytime driving (600 lux), tunnel driving (daytime and nighttime; 100 lux), nighttime driving (3 lux), and sunlight condition. The daytime, tunnel, and nighttime driving involved looking at a corresponding driving scene projected on the front screen under a specific illuminance level, which was controlled by the indoor lighting system. The sunlight condition involved looking outside through the room window instead of looking at the front screen. A driving simulator was implemented using a car seat, a gaming steering wheel, and a beam projector. Two tablet PCs with an 8.0-inch screen of 9.8 (height) × 6.13 (width) cm (Galaxy Tab A 8.0 2017, Samsung Electronics, South Korea) were used as E-mirror displays. The E-mirror brightness could be manually adjusted using the steering wheel buttons, which were connected to the two tablet PCs. The SCANeRTM studio (v1.1, Oktal, France) driving scenes corresponding to each illumination condition were used in this study. Two distinct driving scenarios were considered. The first driving scenario was for daytime ambient light conditions, and consisted of the first daytime driving (DD1), first daytime tunnel driving (DTD1), DD2, DTD2, DD3, and daytime sunlight driving (DSD). In this scenario, DTD induced dark adaptation, and DD induced light adaptation. The second scenario was for nighttime driving, and consisted of the first nighttime driving (ND1), first nighttime tunnel driving (NTD1), ND2, NTD2, ND3, and nighttime sunlight driving NSD. ND involved dark adaptation, whereas NTD involved light adaptation. Both DD1 and ND1 were included to reduce the effect of the ambient light condition outside of the experimental room. The E-mirror brightness could increase or decrease by 10 within the range of 0-200 using the tablet PC brightness control function. The brightness of both tablet PCs was adjusted synchronously. For data analysis, the mean luminance (nit, cd/m2) of the image displayed on the left E-mirror was used. The luminance levels of the E-mirror images for the daytime, tunnel, and nighttime driving ranged from 1.5-184.4, 0-3.0, and 0-3.0 nit, respectively. The preferred luminance levels during eye adaptation were obtained every 15 s for the first 5 min and every 30 s for the remaining period of 5-30 min. The preferred luminance level after completion of each eye adaptation was measured using an ascending-descending series. During the eye adaptation period, the preferred luminance levels for ND1 were significantly different from those for ND3, which could be largely due to the carryover effects of pre-ambient light condition. The final difference in the preferred luminance levels between ND1 and ND3 was observed at 1,215s (20.25 min). In addition, significant differences in the preferred luminance were observed during the first min between DSD and NSD. The results of nighttime driving and sunlight driving indicated that the E-mirror luminance should be adjusted during the first 1,000 to 1,200 s for dark adaptation and the first 60 s for light adaptation. Eye adaptation inside the tunnel was completed during the first 15s for DTD1 and NTD1. However, there was no significant difference between DTD2 and NTD2 except for the time of 0s. Therefore, light and dark adaptation during tunnel driving appeared to be completed within 15 s. During the post-eye adaptation period, the effect of the pre-ambient light condition on the preferred luminance levels disappeared. The mean (SE) preferred luminance (nit) in the post-adaptation phase for the daytime, tunnel, nighttime, and sunlight driving was 126.1 (3.4), 1.5 (0.1), 0.8 (0.1), and 138.9 (3.7), respectively. The mean (SD) illuminance (lux) for DSD and NSD was 1404.7 (265.7) and 1339.9 (239.4), respectively. Some conditions showed significant differences between the initial and final preferred luminance levels. The preferred luminance levels decreased for ND1 and ND2, whereas the preferred luminance levels increased for NSD. Dark adaptation to the nighttime driving illuminance and light adaption to the extreme illuminance both affected the preferred luminance levels. These findings support the need for gradual luminance adjustment of E-mirrors during eye adaptation. Overall, this study showed that the preferred E-mirror luminance levels were affected by previous and current ambient light conditions. Several limitations of this study should be addressed in future studies. First, this study considered the preferred E-mirror luminance only and did not consider driving performance measures. Second, although the illuminance conditions considered in this study were carefully selected to represent distinct ambient light conditions encountered during driving, it is still necessary to examine additional illuminance conditions representing diverse driving contexts. Thus, in addition to the scenarios considered in this study, additional scenarios (e.g., different illuminance levels for daytime, tunnel, nighttime, and sunlight driving than those considered in this study as well as more rapid illuminance-changing cases) should be considered in future studies.

Photoresponses of human rods in vivo derived from paired-flash electroretinograms

1997 ◽  
Vol 14 (1) ◽  
pp. 73-82 ◽  
Author(s):  
David R. Pepperberg ◽  
David G. Birch ◽  
Donald C. Hood
Keyword(s):  
Time Course ◽  
Light Adaptation ◽  
Impulse Response Function ◽  
Test Flash ◽  
Rod Photoreceptor ◽  
Full Time ◽  
Flash Intensity ◽  
Rod Response

AbstractIn the human eye, domination of the electroretinogram (ERG) by the b−wave and other postreceptor components ordinarily obscures all but the first few milliseconds of the rod photoreceptor response to a stimulating flash. However, recovery of the rod response after a bright test flash can be analyzed using a paired-flash paradigm in which the test flash, presented at time zero, is followed at time t by a bright probe flash that rapidly saturates the rods (Birch et al., 1995). In ERG experiments on normal subjects, the hypothesis that a similar method can be used to obtain the full time course of the rod response to test flashes of subsaturating intensity was tested. Rod-only responses to probe flashes presented at varying times t after the test flash were used to derive a family of amplitudes A(t) that represented the putative rod response to the test flash. These rod-only responses to the probe flash were obtained by computational subtraction of the cone-mediated component of each probe flash response. With relatively weak test flashes (11–15 scot-td-s), the time course of the rod response to the test flash derived in this manner was consistent with a four-stage impulse response function of time-to-peak ≃170 ms. A(170), the amplitude of the derived response at 170 ms, increased with test flash intensity (Itest) to a maximum value Amo and exhibited a dependence on Itest given approximately by the relation, A(170)/Amo = 1 - exp(-kItest), where k = 0.092 (scot-td-s)−1. In steady background light, the falling (i.e. recovery) phase of the derived response began earlier, and the sensitivity parameter k was reduced several-fold from its dark-adapted value. As the sensitivity, kinetics, and light-adaptation properties of the derived response correspond closely with those of photocurrent flash responses previously obtained from isolated rods in vitro, it was concluded that the response derived here from the human ERG approximates the course of the massed in vivo rod response to a test flash.

scholarly journals Visual pigment and photoreceptor sensitivity in the isolated skate retina.

1978 ◽  
Vol 71 (4) ◽  
pp. 369-396 ◽  
Author(s):  
D R Pepperberg ◽  
P K Brown ◽  
M Lurie ◽  
J E Dowling
Keyword(s):  
Dark Adaptation ◽  
Visual Pigment ◽  
Response Curve ◽  
Time Course ◽  
Light Adaptation ◽  
Receptor Sensitivity ◽  
Strong Light ◽  
Receptor Response ◽  
Intensity Response ◽  
Isolated Retina

Photoreceptor potentials were recorded extracellularly from the aspartate-treated, isolated retina of the skate (Raja oscellata and R. erinacea), and the effects of externally applied retinal were studied both electrophysiologically and spectrophotometrically. In the absence of applied retinal, strong light adaptation leads to an irreversible depletion of rhodopsin and a sustained elevation of receptor threshold. For example, after the bleaching of 60% of the rhodopsin initially present in dark-adapted receptors, the threshold of the receptor response stabilizes at a level about 3 log units above the dark-adapted value. The application of 11-cis retinal to strongly light-adapted photoreceptors induces both a rapid, substantial lowering of receptor threshold and a shift of the entire intensity-response curve toward greater sensitivity. Exogenous 11-cis retinal also promotes the formation of rhodopsin in bleached photoreceptors with a time-course similar to that of the sensitization measured electrophysiologically. All-trans and 13-cis retinal, when applied to strongly light-adapted receptors, fail to promote either an increase in receptor sensitivity or the formation of significant amounts of light-sensitive pigment within the receptors. However, 9-cis retinal isin. These findings provide strong evidence that the regeneration of visual pigment in the photoreceptors directly regulates the process of photochemical dark adaptation.

scholarly journals Research on Light-Dark Adaptation of Human Vision in Tunnel Portals

2021 ◽  
Author(s):  
Changjiang Liu ◽  
Qiuping Wang
Keyword(s):  
Experimental Data ◽  
Dark Adaptation ◽  
Light Adaptation ◽  
Human Vision ◽  
Adaptation Process ◽  
Recognition Time ◽  
Design Data ◽  
Adaptation Time ◽  
The Relationship ◽  
Tunnel Portal

Abstract To study the characteristics of light and dark adaptation in tunnel portal sections and to determine the influencing factors of light-dark vision adaptation, basic tunnel lighting and linear design data are obtained. In this paper, we use a light-shielded tent to simulate the dark environment of a tunnel in experiments, observe the driver recognition time of target objects during the light-dark adaptation process, and analyze the light-dark adaptation time of human vision. Based on a large number of experimental data, we examined the relationship between age, gender, illuminance and light and dark adaptation times and established a model of the relationship between age, illuminance and light and dark adaptation times. The experimental results revealed that the dark adaptation time is generally longer than the light adaptation time. The dark adaptation time is positively related to age and basically exhibits a cubic relationship. There is no significant correlation between the light adaptation time and age, but the overall trend is that the light adaptation time gradually increases with increasing age. There is no correlation between gender and light and dark adaptation times, but there is a notable correlation between the light and dark adaptation times and illuminance. When the illuminance ranges from 11000-13000 lux, the light and dark adaptation times are the longest.

Is There Any Difference in Human Pupillary Reaction to Acupuncture between Light- and Dark-Adaptive Conditions?

2012 ◽  
Vol 30 (2) ◽  
pp. 109-112
Author(s):  
Hidetoshi Mori ◽  
Hiroshi Kuge ◽  
Tim Hideaki Tanaka ◽  
Yuya Kikuchi ◽  
Hiroshi Nakajo ◽  
...  
Keyword(s):  
Dark Adaptation ◽  
Light Adaptation ◽  
Pupil Diameter ◽  
Acupuncture Point ◽  
Pupillary Response ◽  
Acupuncture Stimulation ◽  
Pupillary Responses ◽  
Significant Difference ◽  
Pupil Constriction ◽  
Adaptation Experiment

Objectives To determine if acupuncture stimulation elicits a pupillary response under light adaptation and whether there is any difference in the pupillary response between light and dark adaptation environments during acupuncture stimulation. Methods The participants consisted of 55 healthy individuals who had no known eye diseases or pupil abnormalities. Experiment 1 compared pupillary responses between acupuncture stimulation and no-stimulation groups under light adaptation. Experiment 2 compared pupillary responses to acupuncture between two conditions (dark and light adaptation) with a two-period repeated measurement crossover design. For both experiments the pupil diameter was continuously measured for 3 min before stimulation, during stimulation and for 3 min after stimulation. For all acupuncture stimulation interventions an acupuncture needle was inserted superficially at the TE5 acupuncture point followed by gentle tapping stimulation for 90 s. Results In experiment 1 the pupil diameter was significantly decreased during (p<0.01) and after stimulation (p<0.0001) compared with the pupil diameter before stimulation under light adaptation. No significant difference was noted in the serial changes in pupil diameter in the no-stimulation group. In experiment 2 the pupil diameter was significantly decreased 90 s after stimulation (p<0.05) and 150 s after stimulation (p<0.05) under light adaptation conditions. Furthermore, the pupil diameter was significantly decreased 120 s after stimulation (p<0.05) and 150 s after stimulation (p<0.01) under dark adaptation conditions. No significant difference in the serial changes in pupil diameter was noted between the groups. Conclusions This study shows that pupil constriction occurs following acupuncture stimulation under light adaptation and this response is no different from that seen under dark adaptation.

The Sensitivity of the Ventral Nerve Photoreceptor of Limulus Recovers after Light Adaptation in Two Phases of Dark Adaptation

1986 ◽  
Vol 41 (5-6) ◽  
pp. 657-667 ◽  
Author(s):  
I. Claßen-Linke ◽  
H. Stieve
Keyword(s):  
Dark Adaptation ◽  
Time Course ◽  
Light Adaptation ◽  
Light Flash ◽  
Light Response ◽  
Receptor Potential ◽  
Second Phase ◽  
Two Phases ◽  
Ventral Nerve Photoreceptor ◽  
External Calcium

The time course of the recovery of the sensitivity of the Limulus ventral nerve photoreceptor was measured during dark adaptation following light adaptation by a bright 1 or 5 s illumination. The stimulus intensity ICR of a 300 μs light flash evoking a response of criterion amplitude (receptor potential or receptor current under voltage clamp conditions) was used as measure of sensitivity.The time course of dark adaptation shows two phases with time constants in the range of 5-9 s and 300-500 s (15 °C). Only the first of the two phases is significantly changed when the extracel- lular Ca2+-concentration is varied.The power function ICR = a·Io-tDA-b gives a good data fit for each of the two phases of dark adaptation. In the first phase the factor ax and the exponent bx are decreased when the external calcium is lowered from 10 mmol/1 to 250 μmol/1. Conversely a1 and b1 are increased when the Ca2+-concentration is raised to 40 mmol/1. For the second phase neither a2 nor b2 is changed significantly upon the changes in calcium concentration in the same experiments.The two phases of dark adaptation reflect the behaviour of the two components C1 and C2 of the electrical light response (receptor potential or receptor current). Under the conditions described here C, determines the size of the light response during the first phase of dark adaptation whereas C2 mainly influences the size of the response during the second phase.Interpretation: The fast first phase of dark adaptation is determined by the change in intracellu- lar Ca2+-concentration. The slower second phase of dark adaptation is not primarily calcium- controlled.

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