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It may also be of unknown cause. 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 ...
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 ...
A 2012 review could not find strong evidence for any single cause, although many theories have been discredited. [35] Twin studies indicate that at least some genetic factors are involved. [ 27 ] [ 36 ] [ 37 ] Myopia has been increasing rapidly throughout the developed world, suggesting environmental factors are involved.
Dilation and constriction of the pupil. Pupillary response is a physiological response that varies the size of the pupil, via the optic and oculomotor cranial nerve.. A constriction response (), [1] is the narrowing of the pupil, which may be caused by scleral buckles or drugs such as opiates/opioids or anti-hypertension medications.
Anisocoria has various causes: [3] Physiological anisocoria: About 20% of population has a slight difference in pupil size which is known as physiological anisocoria. In this condition, the difference between pupils is usually less than 1 mm. [4] Horner's syndrome
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.
In this condition the distance between the inner eye corners as well as the distance between the pupils is greater than normal. Hypertelorism should not be confused with telecanthus, in which the distance between the inner eye corners is increased but the distances between the outer eye corners and the pupils remain unchanged. [3]
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.