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Contractions of the iris dilator muscle, a smooth muscle of the eye running radially in the iris, [2] can cause irregular distortion of the pupil, thus making the pupil look tadpole shaped and giving this condition its name. Episodic segmental iris mydriasis was first described and termed “tadpole pupil” in 1912 by HS Thompson. [1]
Dilation of the pupil in an eye with synechia can cause the pupil to take an irregular, non-circular shape (dyscoria) as shown in the photograph. If the pupil can be fully dilated during the treatment of iritis, the prognosis for recovery from synechia is good. This is a treatable status. To subdue inflammation, topical corticosteroids can be used.
Anisocoria has various causes: [3] Physiological anisocoria: About 20% of the 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 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. [7] In an eye without polycoria, the sphincter muscle is a part of the iris that functions to constrict and dilate the pupil.
Dyscoria, a potential cause of anisocoria, refers to an abnormal shape of the pupil which may be due to developmental and intrauterine anomalies. [4] [verification needed] If the abnormal eye remains dilated when shined with light, it is a pathological small pupil. [citation needed]
The effect of spherical aberration (a fourth-order aberration) increases as the fourth power of the pupil diameter. Doubling pupil diameter increases the spherical aberration component by a factor of 16. [7] Thus, a small change in pupil size can cause a significant change in spherical aberration.
Few people have spent time gazing into a sheep’s eyes, but if you have, you may have noticed something very strange about their pupils. Instead of being round, as is the case with humans, they ...
Nerves involved in the resizing of the pupil connect to the pretectal nucleus of the high midbrain, bypassing the lateral geniculate nucleus and the primary visual cortex. From the pretectal nucleus neurons send axons to neurons of the Edinger-Westphal nucleus whose visceromotor axons run along both the left and right oculomotor nerves .