Synonyms for monocularly or Related words with monocularly
Examples of "monocularly"
The red-green duochrome test is performed
, and is used to refine the spherical component of the refraction. It is based on the principles of chromatic aberration; red (longer wavelength) is refracted less than green (the shorter wavelength). Therefore, a myope (generally with a longer axial length) sees red clearer as red focuses closer to retina than green. The examiner asks the patient: "Do the black letters stand out more on the red or green background? Or do they appear equal?"
Hering's law can be simplified as (1) points falling on the same visual line seem to come from the same location; (2) visual directions are relative to the a unique egocenter (also called cyclopean eye) and (3) the perceived direction of a cyclopean line is the line that intersects the point of fixation. In other words, when seen
a point appears in the direction of that point relative to the eye, but as if seen from the egocenter.
David Hubel and Torsten Wiesel (who won the Nobel prize in Physiology for their elucidation of receptive field properties of cells in primary visual cortex) first performed the technique in felines. Cats (or kittens), although less-closely related evolutionarily to humans even than rodents, have a remarkably similar visual system to humans. They found that ocular dominance columns (the orderly clustering of V1 neurons representing visual input from one or both eyes) were dramatically disrupted when one eye was sewn shut for 2 months. In the normal feline, about 85% of cells are responsive to input to both eyes; in the
-deprived animals, no cells receive input from both eyes.
In a similar experiment, Antonini and Stryker (1993) examined the anatomical changes that can be observed after monocular deprivation. They compared geniculocortical axonal arbors in
deprived animals in the long term (4- weeks) to short term (6–7 days) during the critical period established by Hubel and Wiesel (1993). They found that in the long term, monocular deprivation causes reduced branching at the end of neurons, while the amount of afferents allocated to the nondeprived eye increased. Even in the short term, Antonini and Stryker (1993) found that geniculocortical neurons were similarly affected. This supports the aforementioned concept of a critical period for proper neural development for vision in the cortex.
In rats, digestion of PNNs using the bacterial enzyme chondroitinase ABC reactivates the visual critical period. Specifically, digestion of PNNs in the visual cortex well after the closure of the critical period (postnatal day 70) reactivated critical period plasticity and allowed ocular dominance shift to occur. However, the effects of monocular deprivation in the reactivated case were not as strong as monocular deprivation during a normal critical period. Additionally, in adult rats that had been
deprivated since youth, digestion of PNNs brought about a full structural and functional recovery (recovery of ocular dominance, visual acuity, and dendritic spine density). However, this recovery only occurred once the open eye was sutured to allow the cortical representation of the deprived eye to recover.
The chameleon predator avoidance response is vision-mediated. In predator avoidance, chameleons use minimal head movement and a unique method to monitor potential threats. Due to nodal point separation, a chameleon can judge distance to a potential threat with minimal head movement needed. When confronted with a potential threat, chameleons rotate their slender bodies to the opposite side of their perch to avoid detection. They will keep moving around the branch to keep the branch between themselves and the threat and to keep the threat in their line of sight. If the branch is narrow, a chameleon can observe a threat binocularly around the branch. While a wide branch might present a difficulty in depth perception to another lizard as it is forced to view the threat
, a chameleon due to corneal accommodation and nodal point separation can judge distance between itself and a potential threat with only one eye viewing the threat.
The combination of a negative lens and a positive cornea in the chameleon eye allow for accurate focusing by corneal accommodation. Using corneal accommodation for depth perception makes the chameleon the only vertebrate to focus
. While sight is primarily independent in the two chameleon eyes, the eye that first detects prey will guide accommodation in the other eye. Contrary to previous thought that chameleons used stereopsis (both eyes) for depth perception, research has shown monocular focusing to be more likely. Corneal accommodation however can be coupled, depending on the chameleon's step in the predation sequence, coupled vision meaning the eyes independently focus on the same object. When scanning the environment and in judging distance to prey, vision and accommodation are uncoupled: the eyes are focusing on different objects, such as the environment and the newly-sighted prey. Immediately before the chameleon's characteristic tongue is extended, accommodation in both eyes is coupled: both eyes focus independently on the prey. Imprecise alignment of the images from each eye, as demonstrated by measuring various angles from eye to target, shows that stereopsis is unlikely for depth perception in the chameleon.
Copyright © 2017