Anisocoria is the pupils of the eyes of different sizes in one person. Anisocoria can develop due to eye injury, damage to the fibers that transmit nerve impulses to the muscle responsible for the constriction of the pupil or for its increase in size. 

Anisocoria can often occur when the eye is damaged by a blunt object. After that, the pupil first becomes smaller, then sharply expands and ceases to respond to light stimulation. The inflammatory process of the iris of the eye, as a rule, causes a significant constriction of the pupil. The ischemic state of the iris in the case of angle-closure glaucoma causes a sharp expansion of the pupil of the eye and the subsequent reduction of all reactions of the damaged pupil. As a rule, this causes pain in the eyeball, and vision in the affected eye deteriorates. The abnormal shape of the eye pupil most often indicates local injury to the iris.

Strengthening of anisocoria under the influence of light is a symptom of a disorder of the innervation of the eye of a parasympathetic nature, which most often occurs accompanied by an expansion of the pupil. The most common cause of this pathological phenomenon is damage to the nerve responsible for the movement of the eyeball.

Compression of the nerve of the movement of the eyeball can develop due to neoplasms, aneurysms. Another cause of this disorder is damage to the accumulation of nerve cells in the orbit area due to infectious reasons, trauma or ischemic conditions, for example, in diabetics. In such a situation, the response of the eye pupil to light stimulation is disturbed, but the accommodative response is normal. When “tuning” the eye pupil into the distance, it begins to grow very slowly. In the case of Adie syndrome, slow pupil dilation is combined with a disorder of vision clarity. This condition in ophthalmology is considered benign and often occurs in women at a young age.

In the case when anisocoria is aggravated by the distance of the light stimulus, it is related to the so-called Horner’s syndrome. This condition is sometimes referred to as simple anisocoria. Due to the specific location of the eyelids, from time to time there is a feeling that one eye is a little deeper than the other in the orbit. At the same time, the processes of accommodation of the eyeball and vision itself are not disturbed. Horner’s syndrome occurs for neurological reasons – it can be damage to the trunk or cervical spine, for example, during the development of a tumor in the specified area. In addition, oncology of the upper lung region can lead to this pathology. In pulmonary oncology, Horner’s syndrome is accompanied by painful sensations radiating to the middle of the arm, sharpening of the features of the hand.

In addition, sympathetic fibers can undergo compression due to the phenomenon of “cervical rib”, swelling of the cervical lymph nodes, thyroid cancer, injury or surgery, an inflammatory process in the skull, thrombosis of the carotid artery. In case of detachment of the carotid artery due to an injury, Horner’s syndrome is accompanied by pain in the face and circulatory disorders in the brain from the side of the lesion.

Simple anisocoria is common. In this disease, the difference in the size of the pupils of the eyes may be slight. In some cases, anisocoria may be unstable. But even with such a feature of the course of the disease, accommodative reactions and reactions to light stimuli remain normal.