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Polycoria is a pathological condition of the eye characterized by more than one pupillary opening in the iris. [1] It may be congenital or result from a disease affecting the iris. [ 1 ] It results in decreased function of the iris and pupil, affecting the physical eye and visualization.
In very bright light, the slit-like pupil closes very narrowly over the eye, reducing the amount of light on the sensitive retina, and improving depth of field. Big cats have pupils that contract to a round point. Variation in color of cats' eyes in flash photographs is largely due to the reflection of the flash by the tapetum. A closeup of a ...
To see it, one must be in a dark room, with one eye closed; one must look straight ahead while moving a light back and forth in the field of the open eye. Then one should see the sixth Purkinje as a dimmer image moving in the opposite direction. The Purkinje tree is an image of the retinal blood vessels in one's own eye, first described by ...
The person then closes one eye, and then the other. The person should notice that the target appears larger to the eye that it is directly in front of. When this object is viewed with both eyes, it is seen with a small amount of aniseikonia. The principles behind this demonstration are relative distance magnification (closer objects appear ...
A mydriatic pupil will remain excessively large even in a bright environment. The excitation of the radial fibres of the iris which increases the pupillary aperture is referred to as a mydriasis. More generally, mydriasis also refers to the natural dilation of pupils, for instance in low light conditions or under sympathetic stimulation.
The Cat in the Hat shows his protégé, Young Cat, that while reading with one's eyes closed can be amazing, it can be a strain. When one reads with their eyes open, they will be able to learn a large amount of wonderful things, some of which are shown through illustrations.
Consider a pair of spectacles to correct for myopia with a prescription of −1.00 m −1 in one eye and −4.00 m −1 in the other. Suppose that for both eyes the other parameters are identical, namely t = 1 mm = 0.001 m, n = 1.6, P = 5 m −1 , and h = 15 mm = 0.015 m.
The pupil is a hole located in the center of the iris of the eye that allows light to strike the retina. [1] It appears black because light rays entering the pupil are either absorbed by the tissues inside the eye directly, or absorbed after diffuse reflections within the eye that mostly miss exiting the narrow pupil.