Anisocoria is an ophthalmosyndrome, manifested by different diameters of the right and left pupils. It is observed in a number of ocular and neurological diseases. Pronounced changes are accompanied by a disorder of spatial perception, distortion of the image under consideration, increased visual fatigue. Diagnostics includes the study of the characteristics of the reaction of the pupils, biomicroscopy of the eye, diaphanoscopy, research with M-cholinomimetics. Treatment tactics are determined by the underlying pathology. In case of eye injuries, surgery is indicated, in case of damage to the nerve ganglia, neurostimulation is indicated. When the iris is inflamed, antibacterial agents and NSAIDs are used.
Anisocoria is an important diagnostic criterion in clinical ophthalmology, indicating a direct lesion of the organ of vision or the presence of neurological disorders. There are no statistical data on the prevalence of this condition. Pathology can occur at any age, but such defects occur more often in young people. In childhood, prolonged anisocoria in 34% of cases entails the development of secondary complications in the form of refractive errors. The ratio of women and men with this disorder is – 2:1. This is due to the fact that female individuals are much more likely to have a tonic pupil of Adi.
Causes of anisocoria
The uneven size of the pupils is quite common, but the cause of this condition is not always possible to establish, so some cases are attributed to the idiopathic form. Such disorders can be a symptom of both organic defects of the membranes of the eye and dysfunction associated with pathology of the autonomic nervous system. The main reasons for the development of anisocoria are:
- The use of medicines. With unilateral instillation of M-cholinolytics or M-cholinomimetics, the pupil size changes for a while. Such disorders persist until the drug is removed from the body or before the introduction of drug antagonists.
- Gorner’s syndrome. With oculosympathetic syndrome, ophthalmic symptoms occur a second time against the background of other diseases. Gorner’s syndrome is based on central, post- or preganglionic damage to sympathetic nerve fibers.
- Irith. With inflammation of the iris of the eyeball, the pupillary opening on the side of the lesion narrows. As a rule, clinical manifestations of iritis are leveled after the use of NSAIDs. With the formation of synechiae between the pupillary edge and the anterior surface of the lens, anisocoria persists for a long time.
- Argyle Robertson syndrome. This phenomenon is based on a specific infection of the eyes with neurosyphilis, less often diabetic neuropathy. The peculiarity of the condition is the preservation of the ability of the pupils to accommodate in the absence of a reaction to light fluctuations.
- Holmes-Adi syndrome. With this neurological disorder, there is a monotonous dilation of the pupil in combination with a delayed reaction to light. The accommodative ability is characterized as a vividly close dissociation, which is paradoxical in the described case.
- Traumatic injuries. Violation of the function of the dilator or sphincter of the pupil is often caused by a rupture of the pupillary edge of the iris, which is caused by penetrating wounds of the eyeball. Anisocoria may be a consequence of the formation of peripheral slit-like defects of the iris.
- Oculomotor nerve paralysis. When the third pair of cranial nerves is damaged, the pathology of the pupil is accompanied by ptosis and total atony of the external muscles of the eyeball. The use of cholinergic drugs in medium and high dosages can temporarily change the parameters of the pupillary opening.
Unilateral use of M-cholinolytics leads to temporary blocking of M-cholinergic receptors of parasympathetic nerve endings, which potentiates pupil dilation. M-cholinomimetics have the opposite effect, since they play the role of a mediator. Normally, acetylcholine, interacting with the receptor apparatus, leads to a narrowing of the pupillary opening. The severity of the ciliospinal reflex in Gorner’s syndrome is reduced due to direct damage to the sympathetic nerves. In case of violation of the transmission of the neuromuscular impulse along the oculomotor nerve, the sphincter and dilator of the pupil do not function.
A complete rupture of the sphincter leads to a total expansion of the pupillary opening. When the dilator is injured, the pupil narrows due to the preservation of the function of the antagonist muscle. Organic defects of the iris lead to the development of anisocoria. The muscles responsible for changing the diameter of the pupil pass through the thickness of the iris, so inflammation, defects or anomalies of the structure cause a violation of their functions. A similar pattern is observed in infections with the penetration of the virus into the membranes of the anterior part of the eyeball. The prolonged course of the inflammatory process provokes the formation of dense connective tissue junctions that interfere with the normal operation of the accommodation apparatus.
All lesions of the pupillary orifice can be conditionally divided into congenital and acquired. Variable pupil sizes can be persistent and transient, with an intermittent variant, the diameter is restored after the completion of the trigger factor, with a persistent one, it persists for a long time. There are two main forms of pathology:
- Physiological. It is often found in healthy people, can be traced at rest. The difference in the diameter of the pupils does not exceed 1 mm. Visual differences in the size of the pupil opening are preserved regardless of the lighting features.
- Pathological. This form of anisocoria is a symptom of a neurological or ophthalmological disease. The difference in pupils varies widely. The relationship between the size of the pupil and the reaction of the eye to changes in the intensity of illumination is noted.
Symptoms of anisocoria
With a slight difference in the diameter of the pupils, the only symptom is a cosmetic defect. With pronounced anisocoria, there are complaints of distortion of the image in front of the eyes, violation of spatial perception. Dizziness and severe headache develop, which can be stopped only for a short time by taking analgesics. Visual load (working at the computer, reading books, watching TV) is accompanied by increased fatigue. With sudden movements of the eyeballs, the general condition worsens. Visual acuity does not decrease, with Holmes-Adi syndrome, blurred vision is possible.
The clinical picture largely depends on the underlying pathology. In Bernard-Horner syndrome, the symptoms are most pronounced at low light levels, especially in the first few seconds. Sweating is disturbed on the affected side, the iris looks lighter. With isolated oculomotor nerve paralysis, in addition to anisocoria, diplopia, pain syndrome, difficulty closing the eyelid occurs. In patients with pathology of parasympathetic innervation, the size of the pupils differs only in bright light, photophobia is traced.
The most common complication of anisocoria is considered an ocular migraine. The lack of reaction of one of the pupils to changes in the brightness of illumination and uneven light penetration on the retina are the cause of visual perception disorders. There is a spasm of accommodation, which mimics the clinical picture of myopia. Secondary uveitis may occur in patients. Reactive changes on the part of the optic nerve disc are very rarely detected. Patients try to limit the participation of one eye in the act of vision, so the symptoms of false ptosis of the upper eyelid progress over time. Children have a high risk of developing amblyopia.
The diagnosis is based on the results of an objective examination and anamnestic information. During the examination, traumatic eye injuries, syphilis and the use of eye drops are excluded. During the examination, it is found out in which pupil there are pathological changes. The main diagnostic methods include:
- The study of the reaction of pupils to light. In the case of physiological anisocoria, the test result corresponds to the average indicators. In the pathological process, the pupil reacts sluggishly to light, with persistent morphological changes, there is no reaction.
- Examination of the anterior segment of the eye. Biomicroscopy of the eyeball makes it possible to visualize organic lesions. With anisocoria, traumatic injuries of the iris, sphincter or dilator of the pupil are detected.
- Diaphanoscopy. With the help of diaphanoscopy, diagnostic transillumination of eye tissues by a source of transmitted light is performed. The aim of the study was to detect slit–like defects of transillumination along the periphery of the iris.
- Test with M-cholinomimetic. Pilocarpine hydrochloride is usually used for the study. The hypersensitivity of the iris to low concentrations of the drug suggests that the anisocoria is based on the pupil of Adi.
Treatment of anisocoria
Treatment tactics depend on the etiology of the disease. With an oculosympathetic symptom complex, anisocoria can be eliminated through neurostimulation or hormone replacement therapy. If necessary, surgical correction of ptosis, dissection of the posterior synechiae is performed. If the pupil constriction is caused by iritis, nonsteroidal anti-inflammatory and antibacterial agents are included in the treatment package. With a tonic pupil, the symptoms of anisocoria can be leveled by instillation of M-cholinomimetics. With syphilis of the eyes, specific antibacterial therapy is indicated.
Prognosis and prevention
The prognosis is determined by the cause of the development of this condition. With physiological anisocoria, all changes are transient. In the case of organic damage to nerve fibers, the outcome is unfavorable, since the accommodative ability of the pupil is difficult to correct. After suffering oculomotor nerve paralysis, the lost functions, in case of a favorable outcome, are restored within 3 months. Specific preventive measures have not been developed. Nonspecific prevention is reduced to the rational use of medicines for instillation into the conjunctival cavity, timely treatment of inflammation of the iris, the use of personal protective equipment to prevent eye injury.