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Tadpole pupil is diagnosed and characterized by the abnormality of the pupil shape. The pupil can disorient itself in different ways before it returns to its original shape. [6] For example, the pupil may stretch out to a 7 o'clock position, [6] i.e. the pupil points in the same direction the hour hand on a clock would at 7 o'clock.
A coloboma (from the Greek κολόβωμα, meaning "defect") [1] is a hole in one of the structures of the eye, such as the iris, retina, choroid, or optic disc.The hole is present from birth and can be caused when a gap called the choroid fissure, which is present during early stages of prenatal development, fails to close up completely before a child is born.
Some skates and rays have crescent shaped pupils, [16] gecko pupils range from circular, to a slit, to a series of pinholes, [17] and the cuttlefish pupil is a smoothly curving W shape. Although human pupils are normally circular, abnormalities like colobomas can result in unusual pupil shapes, such as teardrop, keyhole or oval pupil shapes.
The size of the pupil, which controls the amount of light entering the eye, is adjusted by the iris' dilator and sphincter muscles. Light energy enters the eye through the cornea, through the pupil and then through the lens. The lens shape is changed for near focus (accommodation) and is controlled by the ciliary muscle.
The extraneous pupil is c. 2.5mm away from the principal pupil. In cases of true polycoria there is an intact sphincter muscle , which contracts and dilates the pupils. [ 5 ] In an eye without polycoria, the sphincter muscle is a part of the iris that functions to constrict and dilate the pupil.
The iris (pl.: irides or irises) is a thin, annular structure in the eye in most mammals and birds that is responsible for controlling the diameter and size of the pupil, and thus the amount of light reaching the retina. In optical terms, the pupil is the eye's aperture, while the iris is the diaphragm. Eye color is defined by the iris.
The main characteristic that distinguishes physiological anisocoria is an increase of pupil size with lower light or reduced illumination, such that the pupils differ in size between the two eyes. At any given eye examination, up to 41% of healthy patients can show an anisocoria of 0.4 mm or more at one time or another.
Adie's pupil is supersensitive to ACh so a muscarinic agonist (e.g. pilocarpine) whose dose would not be able to cause pupillary constriction in a normal patient, would cause it in a patient with Adie's Syndrome. The circuitry for the pupillary constriction does not descend below the upper midbrain, henceforth impaired pupillary constriction is ...