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The pupillary light reflex (PLR) or photopupillary reflex is a reflex that controls the diameter of the pupil, in response to the intensity of light that falls on the retinal ganglion cells of the retina in the back of the eye, thereby assisting in adaptation of vision to various levels of lightness/darkness.
The ability of the rodless, coneless mice to retain a pupillary light reflex was suggestive of an additional photoreceptor cell. [11] In the 1980s, research in rod- and cone-deficient rats showed regulation of dopamine in the retina, a known neuromodulator for light adaptation and photoentrainment. [3]
In humans the ipRGCs contribute to non-image-forming functions like circadian rhythms, behavior and pupillary light reflex. [14] Peak spectral sensitivity of the receptor is between 460 and 482 nm. [14] However, they may also contribute to a rudimentary visual pathway enabling conscious sight and brightness detection. [14]
Melanopsin: in vertebrate retina, mediates pupillary reflex, involved in regulation of circadian rhythms; Photopsin: reception of various colors of light in the cone cells of vertebrate retina; Rhodopsin: green-blue light reception in the rod cells of vertebrate retina; Protein Kinase C: mediates photoreceptor deactivation, and retinal ...
Normally, as part of the pupillary light reflex, the pupil dilates in the dark and constricts in the light to respectively improve vividity at night and to protect the retina from sunlight damage during the day. A mydriatic pupil will remain excessively large even in a bright environment. The excitation of the radial fibres of the iris which ...
Light from a single point of a distant object and light from a single point of a near object being brought to a focus. The accommodation reflex (or accommodation-convergence reflex) is a reflex action of the eye, in response to focusing on a near object, then looking at a distant object (and vice versa), comprising coordinated changes in vergence, lens shape (accommodation) and pupil size.
Although the pupillary response, in which the pupil dilates or constricts due to light is not usually called a "reflex", it is still usually considered a part of this topic. Adjustment to close-range vision is known as "the near response", while relaxation of the ciliary muscle to view distant objects is known as the "far response".
There are about 0.7 to 1.5 million retinal ganglion cells in the human retina. [2] With about 4.6 million cone cells and 92 million rod cells, or 96.6 million photoreceptors per retina, [3] on average each retinal ganglion cell receives inputs from about 100 rods and cones.