Pupils are generally equal in size. They control the amount of light entering the eye. Pupillary function is an important objective clinical sign in patient with visual loss and neurologic diseases and it should be examined in every patient. Anisocoria is a condition characterized by an unequal size of the eyes' pupils.

Although previous studies shows that approximately 20% of the healthy people have essential anisocoria, several causes of anisocoria are life threatening. Adie's tonic pupil (ATP), Oculomotor nerve palsy and Horner disease are three causes of pathologic anisocoria. Unfortunately, individuals with pupillary disturbance like anisocoria may not be aware of any abnormality. May times, these abnormalities are discovered by patients' relatives or friends.

The examiner should assiduously determine the duration of anisocoria. Inspecting a series of old photographs can frequently prove that the anisocoria is not as "newly acquired" as thought. Obviously, acquired anisocoria of recent onset has more ominous implications than anisocoria that dates back many years or even a lifetime.

Many causes of anisocoria are completely benign, although the unnecessary evaluation of these disorders may produce morbidity inadvertently. O-Glass can help clinicians and also patient to evaluate pupil specifications and function.

 Main Reasons of Anisocoria

Adie's Tonic Pupil

The patient with ATP may be totally asymptomatic, and is often brought to a physician's office by a friend or relative who notices that he or she has one large pupil. About 80 percent of patients with ATP may have symptoms such as anisocoria, photophobia, and difficulty with dark adaptation. ATP prevalence is about two cases per 1000 population. The mean age is 32 years, and there is a female predominance (2.6:1) for the idiopathic variety

Oculomotor Nerve Palsy

For a unilateral dilated pupil, the most important condition to look for is an oculomotor nerve palsy. Other signs to look for include ipsilateral ptosis, squint (the eye is deviated downwards and outwards). In pupil-involving oculomotor nerve palsy, it is vital to consider a space-occupying lesion (such as an aneurysm) compressing on the nerve on its route from the brainstem towards the eye.

Horner Disease

Horner syndrome occurs

because of any lesion along the oculosympathetic pathway. With this syndrome, anisocoria is more obvious in dim illumination and the affected pupil shows dilation lag when the room light is abruptly turned off. Miotic pupil is abnormal in this syndrome.