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Eye - Wikipedia, the free encyclopedia   (Site not responding. Last check: 2007-10-10) With each eye viewing a different angle, a fused image from all the eyes is produced in the brain providing a very wide angle high resolution image. As far as the vertebrate/mollusk eye is concerned, intermediate, functioning stages have existed in nature, which is also an illustration of the many varieties and peculiarities of eye construction. Having two eyes is an added complication, because the brain must point both of them accurately enough that the object of regard falls on corresponding points of the two retinas; otherwise, double vison would occur. www.davidson.edu /personal/arbugosh/eyewik.htm   (4531 words)

Adaptation (disambiguation) - Wikipedia, the free encyclopedia Adaptation (biology), an anatomical structure, physiological process or behavioral trait that has evolved Neural adaptation, the ability of neural systems to change their response behaviour depending on the recent stimulus history adaptation (eye), ability of the eye to adjust to various levels of darkness and light en.wikipedia.org /wiki/Adaptation_(disambiguation)   (149 words)

Adaptation (eye) - Wikipedia, the free encyclopedia In ocular physiology, adaptation is the ability of the eye to adjust to various levels of darkness and light. This means that the brightest and the darkest light signal that the eye can sense are a factor of roughly one thousand million apart. However, in any given moment of time, the eye can only sense a contrast ratio of one thousand. en.wikipedia.org /wiki/Adaptation_(eye)   (506 words)

Eye -   (Site not responding. Last check: 2007-10-10) In most vertebrates and some mollusks the eye works by allowing light to enter it and project onto a light-sensitive panel of cells known as the retina at the rear of the eye, where the light is detected and converted into electrical signals, which are then transmitted to the brain via the optic nerve. Such eyes are typically roughly spherical, filled with a transparent gel-like substance called the vitreous humour, with a focusing lens and often an iris which regulates the intensity of the light that enters the eye. However, the development of the eye is considered by many experts to be monophyletic; that is, all modern eyes, varied as they are, have their origins in a proto-eye believed to have evolved some 540 million years ago (Mya). psychcentral.com /psypsych/Eye   (5352 words)

Reference.com/Encyclopedia/Adaptation (eye) In ocular physiology, adaptation is the ability of the eye to adjust to various levels of darkness and light. This means that the brightest and the darkest light signal that the eye can sense are a factor of roughly one thousand million apart. The eye takes approximately 30 minutes to fully adapt from bright sunlight to complete darkness and become one million times more sensitive than at full daylight. www.reference.com /browse/wiki/Adaptation_(eye)   (231 words)

Life Sciences Program Tasks and Bibliography for FY 2000 Details During adaptation, for 5 min a visual display moves so as to ask for a gain of 0 with the head rolled left or pitched up, then for 5 min a gain of 2 is asked for with the head rolled right or pitched down. Adaptation to the centrifugation does occur; three 10-min adaptation sessions produced adaptation that was retained (at reduced level) a week later. Using vertical eye position as a context cue, the initial acceleration of the eyes, when presented with a moving target, can be made to decrease with the eyes elevated, and to increase with the eyes depressed. peer1.nasaprs.com /cfpro/peer_review/ltb1_00.cfm?id=138   (1838 words)

The Ultimate Eye Dog Breeds Information Guide and Reference The eye is typically roughly spherical, filled with a transparent gel-like substance called the vitreous humour, with a focusing lens and often a muscle called the iris that controls how much light enters. How a complex structure like the eye could have evolved is often said to be a difficult question for the theory of evolution, on the basis that intermediate forms of an eye would presumably have been of little use, and light-sensitive organs are present in a variety of different creatures without any clear evolutionary link. However, eyes in different levels various animals show adaption to their requirements (for example, birds of prey have much greater visual acuity than humans), and the different forms of eye in, for example, vertebrates and mollusks are often cited as examples of parallel evolution. www.dogluvers.com /dog_breeds/Eye   (624 words)

The Eye and Night Vision The anterior portion of the eye is essentially a lens system, made up of the cornea and crystalline lens, whose primary purpose is to focus light onto the retina. It is caused by the position of the optic nerve in the rear of the eye. While dark adaptation of the rods develops rather slowly over a period of 20 to 30 minutes, it can be lost in a few seconds of exposure to bright light. www.narcap.org /TheEyeandNightVision.htm   (4531 words)

ADAPTATION The narrowing is the objective manifestation of the mechanism's adaptation. Just the same criterion for adaptation may be used in judging the behavior of the free-living animal in its learned reactions. Adaptation can occur in several levels of an organizational hierarchy and may even apply to itself as in "amplifying adaptation" (Ashby) which is "adaptation to adapt" and has the properties of self-organization. pespmc1.vub.ac.be /ASC/ADAPTATION.html   (658 words)

Veg Cultivars, Southernpea   (Site not responding. Last check: 2007-10-10) Adaptation: for use as a home garden and fresh market cultivar for spring, midseason, and fall plantings throughout the southeastern United States, and for processing for the frozen food industry. Adaptation: for use by the frozen food industry throughout the southeastern United States as a replacement for White Acre. Adaptation: for use in Alabama "because of its special appeal to pick-your-own consumers, as well as fresh-market production for wholesale lots in the pod or retail sale of shelled peas." Ala. cuke.hort.ncsu.edu /cucurbit/wehner/vegcult/southernpea.html   (3251 words)

Adaptation | Chromatic Adaptation | Light Adaptation | Dark Adaptation | Transient Adaptation | Transient Adaptation ... Since there are several types of receptive cells in the eye, which are sensitive to different bands in the visible spectrum, the adaptation also manages the "white balance" of the eye, by chromatic adaptation. Transient Adaptation is a special case, where the human eye has to adapt from low to high light levels and back in short intervals. The Transient Adaptation Factor (TAF) defines the relative amount by which the equivalent contrast is reduced due to readaptation from one luminous background to another. www.schorsch.com /kbase/glossary/adaptation.html   (453 words)

Evolution: Library: Evolution of the Eye Darwin acknowledged from the start that the eye would be a difficult case for his new theory to explain. Through natural selection, different types of eyes have emerged in evolutionary history -- and the human eye isn't even the best one, from some standpoints. Here's how some scientists think some eyes may have evolved: The simple light-sensitive spot on the skin of some ancestral creature gave it some tiny survival advantage, perhaps allowing it to evade a predator. www.pbs.org /wgbh/evolution/library/01/1/l_011_01.html   (557 words)

Susanne Ferber - Recent Findings Thus, before and after PA he was aware of the fact that the stimuli he had been exploring consisted of full faces but he was not aware of the fact that the emotional expression of the two halves of the faces did not match. We conclude that while the exploratory eye movements of a patient with neglect were clearly shifted after PA, he still showed no awareness for the left side of the stimuli he was now actively exploring. Prism adaptation modulates functions of the parietal lobe, such as the control of eye movements, but fails to influence the underlying mechanisms of neglect. www.psych.utoronto.ca /~ferber/findings.html   (399 words)

View Study [NEI Clinical Studies]   (Site not responding. Last check: 2007-10-10) Preliminary studies from two eye care centers reported that the use of prisms on eyeglasses for about a month before surgery led to good results after a single operation in more than 90 percent of patients. During the surgery, the muscles are detached from the eye and moved back a certain distance based on the amount of misalignment. The prism adaptation process appears to result in a higher percentage of patients with well-aligned eyes after surgery and a lower rate of re-operation. www.nei.nih.gov /neitrials/viewStudyWeb.aspx?id=20   (887 words)

Sunset science. III. Visual adaptation and green flashes The colors perceived by an eye viewing some light while in a neutral state of adaptation, an eye that has become adapted to this light (or to some other), or an eye viewing a color photograph of the light, all differ. In 1905, von Kries explicitly stated that after red­fatigue, he saw light of the D lines' wavelength (589 nm) as a green­yellow hue matching 556 nm seen in a retinal area that was not fatigued [29]. To confirm the connection between sunsets and visual adaptation, it is necessary to show that the physical circumstances of an observer staring at the setting Sun are those that elicit hue shifts in the laboratory. mintaka.sdsu.edu /GF/papers/JOSA/GF-vis.html   (7537 words)

APStracts 4:166N, 1997.   (Site not responding. Last check: 2007-10-10) To investigate the site of gaze adaptation in primates, we reduced the gain of large head-restrained gaze shifts made to 50­ target steps by jumping the target 40% backwards during a targeting saccade and then tested gain transfer to the eye- and head-movement components of head-unrestrained gaze shifts. However, the adapted peak eye and head velocities were appropriate for the adapted, smaller gaze amplitudes. Therefore, gaze adaptation is most likely to occur upstream of the creation of separate eye and head movement commands. www.uth.tmc.edu /apstracts/1997/jn/August/166N.html   (336 words)

The Inverted Retina: Maladaptation or Pre-adaptation?. Origins & Design 19:2. Denton, Michael J. In all non-vertebrate eyes, and in the pineal or dorsal eyes of primitive vertebrates, the photoreceptors point toward the light. However, in the vertebrate lateral eye, the photoreceptors point backwards away from the light towards the retinal epithelium and the choroidal blood sinuses. This arrangement necessitates the placement of the neural cell layer--which relays the visual image from the retina to the brain--between the photoreceptors and the light, and results in the blind spot where the axons of these neural cells leave the retina for the brain via the optic nerve. www.arn.org /docs/odesign/od192/invertedretina192.htm   (2065 words)

Cole Eye Institute - Research Center After overnight dark adaptation, mice were anesthetized (ketamine/xylazine) and placed on a heating pad. Conclusion: In the mouse eye, the process that underlies the adaptation-induced changes of the cone ERG is influenced by rod activity. This is different from the human eye, wherein these adaptation-induced changes appear to be intrinsic to the cone system. www.clevelandclinic.org /eye/research/retina22.asp   (291 words)

Normal and Adapted Visuooculomotor Reflexes in Goldfish -- Marsh and Baker 77 (3): 1099 -- Journal of Neurophysiology VOR eye velocity with a ratio of 0.6 to 1 to that measured for Eye movements were recorded using the scleral search coil technique with a bandwidth of 0-200 Hz and a sensitivity of 0.2°. The occurrence of an oscillation in eye velocity jn.physiology.org /cgi/content/full/77/3/1099   (8528 words)

Eye - Beat love keys sharp Ginsberg adaptation - 06.03.99 Arguably the most important poem in post-war American literature, Allen Ginsberg's "Howl" (1956) was a classic embodiment of Beat poetry, a movement whose radical influence changed the face of cultural and political life in America in the 1950s and beyond. Threshold Theatre's new adaptation of Howl -- which, sadly, opened and closed last week at Buddies in Bad Times with little fanfare -- is the latest example of the influence of Ginsberg's work. The most striking feature of this gutsy adaptation is its ability to balance a wide range of components. www.eye.net /eye/issue/issue_06.03.99/arts/theatre.html   (555 words)

Two Laboratory Exercises Demonstrating Neural Adaptation: Eye-Hand Coordination and Anticipatory Postural Adjustments ... Then, the student dons a special pair of prismatic goggles that requires the eyes to deviate 15° to the right in order to focus on objects that are straight ahead. Experiments reported in the scientific literature link this example of adaptation to neural plasticity specifically in cerebellar circuits.3,5 Critical reading of such literature is appropriate for advanced students. In addition to adaptation, the cerebellum also contributes to coordination and anticipation.5 The prism adaptation experiment provides a clear example of control over eye-hand coordination. findarticles.com /p/articles/mi_qa3969/is_200504/ai_n13639985   (881 words)

Effects on Visual Acuity and Stereoacuity of Oculomotor Changes Produced by Pre-Flight Adaptation Training   (Site not responding. Last check: 2007-10-10) Because stereopsis requires accurate fixation by both eyes simultaneously, it may be sensitive to smaller discrepancies in the direction or velocity of gaze of the two eyes than those that affect visual acuity. The motion to be detected was internal to the pursuit or fixation target and was either in the direction of eye or head movement, or orthogonal to it. The velocity of uncompensated retinal image motion should be higher and the duration of eye and head movements should be longer after adaptation to microgravity or TTD stimulation, suggesting that the impairment of motion sensitivity during gaze shifts should be larger and more protracted. www.isso.uh.edu /publications/A9798/bedell.htm   (2272 words)

Cross-Axis Adaptation of Pursuit Initiation in Humans -- Hayakawa et al. 42 (3): 668 -- Investigative Ophthalmology & ... The ordinates and the abscissas of the graphs represent vertical and horizontal angles (in degrees) for pursuit traces for the 500-msec segment after the target onset, respectively. Early in training, the eye began moving left in response to the initial leftward target movement. Eye movements were not affected on the reference side. www.iovs.org /cgi/content/full/42/3/668   (3587 words)

Eye Position Specificity of Saccadic Adaptation -- Alahyane and Pélisson 45 (1): 123 -- Investigative ... adaptation with the eyes 25° downward) and alternated from adaptations the efficacy of the BDA and the UDA protocols. Time course of saccadic adaptation in all subjects (A–H), showing plots of the slope of the regression lines illustrated in Figure 4 for subject F.) Comparison of the time course of backward adaptation versus forward adaptation in the BDA and in the UDA condition. www.iovs.org /cgi/content/full/45/1/123   (4822 words)

Prism Adaptation Study (PAS), The [NEI Clinical Studies] Acquired esotropia (crossed eyes that develop after a child reaches the age of 6 months) accounts for 25 percent of all patients with misaligned eyes. The Prism Adaptation Study was a double randomization trial involving 286 patients. Prism adaptation prior to surgery for acquired esotropia (crossed eyes) better aligns eyes, thus decreasing the possible need for additional surgery. www.nei.nih.gov /neitrials/static/study20.asp   (910 words)

Webvision: Light and Dark Adaptation Aubert (1865) was the first to estimate the threshold stimulus of the eye in the dark by measuring the electrical current required to render the glow on a platinum wire just visible. When the same size test spot is used in the peripheral retina during dark adaptation, the typical break appears in the curve representing the cone branch and the rod branch (figure 5). With light adaptation, the eye has to quickly adapt to the background illumination to be able to distinguish objects in this background. webvision.med.utah.edu /light_dark.html   (2369 words)

A local model of eye adaptation for high dynamic range images. — Centro de Ciências e Tecnologias da Computação In the real world, the human eye is confronted with a wide range of luminances from bright sunshine to low night light. Our eyes cope with this vast range of intensities by adaptation; changing their sensitivity to be responsive at different illumination levels. This adaptation is highly localized, allowing us to see both dark and bright regions of a high dynamic range environment. cctc.di.uminho.pt /publications/pub-2004-042   (198 words)

About exotropia, types and treatment, eye turns out, wandering eyes As long as the eyes are straight some of the time, the brain will develop some normal functioning of the eyes (stereoscopic depth perception). This is because the turn usually occurs during times of inattention, fatigue, or distance viewing not during the anxiety-provoking eye examination. Though prisms are effective they are not as effective as vision therapy and may result in adaptation problems so that more prism is necessary in the future to alleviate symptoms. www.strabismus.org /exotropia_eye_turns_out.html   (642 words)

Long-lasting modifications of saccadic eye movements following adaptation induced in the double-step target paradigm -- ... The adaptation of saccadic eye movements to environmental changes Adaptation was more effective and more resistant to recovery of saccade gain related to adaptation were accompanied by a decrease www.learnmem.org /cgi/content/abstract/12/4/433   (308 words)

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