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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
Anisometropia causes some people to have mild vision problems, or occasionally more serious symptoms like alternating vision or frequent squinting. However, since most people do not show any clear symptoms, the condition usually is found during a routine eye exam. [8] For early detection in preverbal children, photoscreening can be used.
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.
A human adult exhibiting voluntary control over his iris muscles, where he can cause his pupil to dilate and constrict on command. A dilation response , is the widening of the pupil and may be caused by adrenaline; anticholinergic agents; stimulant drugs such as MDMA, cocaine, and amphetamines; and some hallucinogenics (e.g. LSD). [3]
Premature sclerosis of lens or ciliary muscle weaknesses due to systemic or local cases may cause accommodative insufficiency. [1] Systemic causes of ciliary muscle weakness include diabetes, pregnancy, stress, malnutrition etc. [1] Open angle glaucoma, Iridocyclitis etc. are known local causes. [1]
Other terminology include anisometropia, when the two eyes have unequal refractive power, [18] and aniseikonia which is when the magnification power between the eyes differ. [19] Refractive errors are typically measured using three numbers: sphere, cylinder, and axis. [20] Sphere: This number denotes the strength of the lens needed to correct ...
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.
Mydriasis is the dilation of the pupil, usually having a non-physiological cause, [3] or sometimes a physiological pupillary response. [4] Non-physiological causes of mydriasis include disease, trauma, or the use of certain types of drugs. It may also be of unknown cause.