Recent Developments in Vision Research (1966) / Chapter Skim
Currently Skimming:
PUPILLARY REACTIONS TO LIGHT
PUPILLARY REACTIONS TO LIGHT
Pages 20-68
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 20... ...
, by filters (paper, parchment, opal glass, milkglass or frosted glass, and later neutral gray gelatine filters or neutral gray glass filters or wedges) , by rotating Nichol prisms or by rotating crossed polaroid filters.
|
From page 21... ...
Experimental Work in Which Stimulus Intensity Was Varied in Connection with Other Problems Year Author Chief problem Year Author Chief problem 1892-93 Bordier visual acuity 1939-40 Hecht ft Pirenne color (owl) 1892,93 Sachs color 1942 Bart ley frequency, ocular discomfort 1900 Abelsdorff color 1903 Friberger speed 1942 Wagman 4 Gulberg color 1903 Schafer color 1948 Barany & Hallden retinal rivalry 1904 Abelsdorff & Feilchenfeld 1948 Morone dazzling, fatigue color 1952 Wirth retinal rivalry 190S Easier color 1956.59 Van der Tweel various 1907 Hess retinal position 1957 Bleichert servo-analysis 1907 Polimanti color 1957 Bleichert & Wagner se rvo - analy gis (frequency)
|
From page 22... ...
Note: Symbols: static = eye adapted to light stimuli; flash n - light pulse; flash |~* = sudden increment; threshold = threshold reactions of dark -adapted eye; difference threshold = increment or decrement of previously steady illumination; darkness = sudden or gradual withdrawal of light.
|
From page 23... ...
In these investigations, different kinds of light stimuli were used: (1) the subject's eye was successively adapted to different levels of brightness of the source, and the pupillary diameter was noted for each intensity step ("static" in Table 2C)
|
From page 24... ...
Using appropriate recording techniques (Lowenstein & Loewenfeld, 1958) , small but distinct pupillary reactions usually can be obtained well within the first log unit of stimulus luminance above the subject's scotopic visual threshold.
|
From page 25... ...
plotted against stimulus luminance, with arrow T marking subject's scotopic visual threshold. Log luminance = .6 - 9.6 above visual threshold for 1-sec light flashes emitted by Sylvania glow modulator tube (with 31 mm condensing lens = slightly divergent beam measuring approximately 20 mm at subject's left cornea)
|
From page 26... ...
. Human scotopic visual threshold marked by white arrows; human visual threshold when using red filter marked by black arrows.
|
From page 27... ...
3. Schematic representation of pupillary light reflex pathway (Fig.
|
From page 28... ...
descending connections from cortex, thalamus and hypothalamus. Note: a£ = anterior commissure; as_ = aqueduct of Sylvius; av = subclavian ansa of Vieussens; £ = cortex; cb_ = cliliospinal center of Budge; ££ = corpus callosum; cg = ciliary ganglion; cis = short ciliary nerves; cil = long ciliary nerves; f_= fornix; gg_ = Gasserian ganglion; gs = ganglion stellatum; ha = habenular nucleus; m = mammillary body; mcg = middle cervical ganglion; mi = massa intermedia; nc = naso-ciliary branch of the ophthalmic 5th nerve; oc = optic chiasm; on = optic nerve; p = pons; p_£ = posterior commissure; p_i = pineal body; scg = superior cervical ganglion; III = (Westphal-Edinger)
|
From page 29... ...
In line A, 1-sec light flashes were presented at times framed (intensity 8-9 log units above scotopic visual threshold)
|
From page 30... ...
The light reflex, however, does not benefit by the large pupillary diameter in darkness; it is supressed when the degree of supranuclear inhibition and sympathetic excitation exceeds an optimal level (Fig.
|
From page 31... ...
. These mechanisms are active to a remarkably similar degree in all mammals, and pupillary reactions elicited under similar experimental conditions show relatively minor variations among species (see Figures 7,8)
|
From page 32... ...
a = Normal light reflex in alert but not excited rat; b-d = inhibited reactions, elicited after sensory stimulation~with increasing emotional excitement, the pupil enlarged and the light reflexes became less and less extensive, showing characteristic w-and v-shapes found in all mammals under similar conditions; £-_£-_£_= light reflexes elicited while the animal was sleepy. Note the square, w-and flattened vshapes of the responses.
|
From page 33... ...
irritation Parasympathetic (nonirritative) nuclear or postnuclear lesion of the third nerve Lesion in the afferent pathways of the light reflex 8 Very large pupils and absence of light reflex, or sluggish, in1 tensive reflex of short duration; bilateral W- or V- shaped light reflex; pupils larger than normal; bilateral Prolonged latent period; pupils slightly larger than normal; sluggish, inextensive light reflex; unilateral or bilateral Prolonged latent period; slower than normal, W- or V- shaped light reflex; pupils remain equal, even in unilateral lesions A normal optimal reactions to light E Peripheral sympathetic lesion Central (diencephalic)
|
From page 34... ...
. Eyes in darkness = a; during 1-sec intervals b, exposed to light stimuli about 8-9 log units above scotopic visual threshold.
|
From page 35... ...
One-second white light stimuli, approximately 2 log units above subject's scotopic visual threshold, were presented at times framed at L^- • First line: Reactions elicited while the subject gradually fell asleep showed enhanced contractions with no redilation in darkness; at c c_c_the subject closed his eyes. Second line: Shortly before 4th light reflex, the subject was awakened by a verbal stimulus ("wake up !
|
From page 36... ...
1929 Barbie ri electric contact 1957-63 Lowenstein electronic tube * 1932 Poursines falling cam shutter 1957-63 Shakhnovitch mechanical shutter *
|
From page 37... ...
Moderate intensity range: It has been mentioned above that the duration of a pupillary contraction to a timed light flash depends on the intensity of the stimulus. The effect of changes in stimulus duration, likewise, is different for dim and for bright light.
|
From page 38... ...
: Dim light was used, about 3 log units above subject's scotopic visual threshold. Reactions to short (a)
|
From page 39... ...
marked by double arrow. Stimulus intensities: 2.6 log units above scotopic visual threshold for solid line, 4.6 log units for broken line, 6.6 log units for dash-dot line, and 8.6 log units for dotted line.
|
From page 40... ...
When the eye has been adapted to light up to about 8 log units above the visual threshold, and this light is suddenly turned off, the pupil re-dilates quickly and in a smooth curve, reaching nearly full dilation within less than one minute. Crawford (1936-37)
|
From page 41... ...
It should be realized, however, that in the intensity range used by Lowenstein for such examinations (8-9 log units above scotopic visual threshold) such a reduction is insignificant, because the stimulus luminance may be decreased by a factor of 100-1000 without significant changes in the reflex shape.
|
From page 42... ...
Such stimulus wave-forms were produced by changing the current to the lamp, or by inserting a rotating Nichol prism, rotating disk shutter, or rotating crossed polaroid filters into the light path. The majority of these studies were chiefly concerned with problems of servo-analysis that fall outside the scope of this review.
|
From page 43... ...
Light source, Sylvania glow modulator tube; light intensity = about 9 log units above scotopic visual threshold; area = about 5°, centrally fixated, with rest of retina illuminated by intraocular stray light. In mammals, the slow smooth-muscle pupillary sphincter is driven into tetanic contraction at low stimulus frequencies.
|
From page 44... ...
13. Pupillary oscillations in pigeon elicited by repeated short light flashes Moments of presentation of 5 ms white light flashes (same as in Fig.
|
From page 45... ...
It is obvious that extent and rate of the pupillary oscillations differ with different stimulus intensities With weak light the pupillary contraction was followed almost immediately by redilation. The pupil regained its dark-adapted diameter within seconds, and showed no more oscillations than it did in darkness (solid line)
|
From page 46... ...
Abscissa showing light intensity in log units above subject's scotopic visual threshold (marked by arrow) ; left-hand ordinate and solid columns representing number of pupillary oscillations within 2-minute periods of steady illumination (averaged numbers of 3 experiments per intensity step)
|
From page 47... ...
It should be mentioned, however, that changes in stimulus luminance due to shading by the iris, giving rise to such marked pupillary movements, should be expected to be visible; but in the experience of the author it was precisely in the medium-intensity range, in which the light looked entirely unchanging to the subject, that the pupillary oscillations were most pronounced, while with weak light, which appeared to come and go throughout the 2-minute period, the pupil was stable. It must be concluded that the mechanism of these movements is yet unexplained.
|
From page 48... ...
have determined the interrelation between the duration of the dark interval and the amount by which the re-appearing light may be reduced in order to cause only a small, standardized pupillary contraction, and have found a gain of about 1 -5 log units in the sensitivity of the pupillary receptor system within the first 2 sec in darkness. This experiment points to a most fascinating field of application, because it appears possible in this manner to test objectively the adaptive effects of very short dark periods.
|
From page 49... ...
. In birds, with a striated sphincter, the minimal latent period is only about 0.06 sec, proving that, for bright light stimuli, the time delay consumed by the nervous reflex mechanism must be very short indeed.
|
From page 50... ...
Stimulus luminance in log units shown by abscissa, where O indicates subject's foveal visual threshold for 1° white light flashes of 1 sec duration; visual threshold for red stimuli (Wratten filter #29) of same area and location marked by arrow.
|
From page 51... ...
21, Lowenstein, etal., 1964a) Average latent periods of pigeon's light reflexes (extents shown in Fig.
|
From page 52... ...
1929 Barbierl 1956 Schweitzer 4 Bourn an * 1931.32 Braun 1956,59 Van der Tweel *
|
From page 53... ...
2. Pupillary movements elicited from the fovea and from the retinal periphery When the eye has been dark-adapted, it is not difficult to obtain pupillary reactions from the retinal periphery.
|
From page 54... ...
; compared pupillary threshold reactions and increment curves to visual thresholds and flicker fusion curves Note: a,b in Year column refers to order in References.
|
From page 55... ...
and pupillary thresholds (broken line) are parallel, with pupil about 1.5 log units less sensitive in this experiment (pupillary reactions detected by observation with infrared-sensitive converter-detector; the values for the pupil tend to become somewhat more sensitive when the reflexes are recorded)
|
From page 56... ...
against stimulus luminance (in arbitrary log units, with 100 per cent maximal intensity available in experiment)
|
From page 57... ...
Pupillary reactions are not unique in this respect. For example, when the visual flicker fusion curves are compared with pupillary increment curves, obtained with the same kind and intensity of stimuli, the low threshold and shallow increment curves for the retinal periphery, and the high threshold and steep increment curves for the fovea are very similar for the two functions (Fig.
|
From page 58... ...
Note the parallelism between the flicker fusion increment curves and the pupillary reflex increment curves of Fig.
|
From page 59... ...
* 0; van der Plank (1934)
|
From page 60... ...
2. Pupillary spectral sensitivity A summary of the results of these experiments follows: The pupillomotor effectiveness of a colored light stimulus is related to its apparent brightness; for each color, the threshold for pupillary reactions lies slightly above the corresponding visual threshold.
|
From page 61... ...
. In each line pupillary thresholds indicated by P, visual thresholds by V; light intensity indicated on abscissa in arbitrary log units, with 4 the maximal intensity available in the experiment.
|
From page 62... ...
In both experiments curves constructed by measuring energy of light of different wave lengths needed to obtain pupillary threshold reactions (0.3-0.5 mm) , with sudden exposure of eye to light, and with relatively large field illuminated (tungsten source and Wratten color filters)
|
From page 63... ...
When the stimulus luminance was increased, however, the effect of stray light was easily recognized: for equal increments in light intensity, the increases in pupillomotor activity were much steeper for blue, green, or white than for red light. Under the same experimental conditions, the visual flicker fusion curves, which are influenced far less by stray light than is the pupil, were precisely parallel for the four colors (Lowenstein, Kawabata, & Loewenfeld, 1964)
|
From page 64... ...
against stimulus luminance as abscissa (in arbitrary log units, with O marking subject's foveal visual threshold to 1-sec white light flashes of 1° area (white arrow)
|
From page 65... ...
Though it was often stated, as it had been at an earlier time about dim white light, that this illumination had only little pupillomotor effect, the results may have differed from those obtained in true darkness. Strictly speaking, then, dark adaptation existed only in those experiments in which the pupillary reactions were recorded by flash photography without other illumination, or were viewed or recorded by infrared-sensitive devices that operated with light beyond the visible spectrum.
|
From page 66... ...
, or adapted to diffuse, blue-green illumination, about 4.5 log units above subject's scotopic visual threshold (broken lines) ; during periods framed at b, bright, white light flashes presented, approximately 9 log units above absolute visual threshold.
|
From page 67... ...
. When the subject is tired, the same background light has a profoundly depressing effect: the pupil becomes quite small, and reflexes to standard light stimuli inextensive and pathological in shape (Fig.
|
From page 68... ...
. These experiments were, however, done without records of the pupillary movements; in view of the great difficulty in judging accurately the small, variable pupillary threshold responses, .especially in dim light, the question cannot be considered as settled.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.