Discoria: Definition, Symptoms, Causes, Types, Diagnosis and Treatment

The pupil is the black central part of the eye. The pupils enlarge (dilate) in dim light and get smaller (contract) in bright light.

Discoria is when human pupils differ in size. Discoria is the medical term used to refer to any abnormality in the shape of the pupil of the eye .

Some people have pupils that are slightly different in size or shape, so the variations can be normal and are generally harmless.

It is generally considered benign, although it must be distinguished from congenital Horner syndrome, drug dilation, or other conditions related to the sympathetic nervous system.

The prevalence of Discoria has not been found to be influenced by the subject’s sex, age, or iris color.

However, if there is a significant difference or if one of the pupils has recently changed, there could be an underlying problem.

The pupil is the hole in the center of the iris (the colored part of the eye) and its main function is to control the amount of light that enters the eye. The pupils do this by contracting and dilating, making them appear smaller and larger respectively.

When your pupils are different sizes, it is called anisocoria and there are several different causes.

Sometimes your pupils will return to normal size without the need for treatment, but you should seek medical attention if the condition persists or trauma or head injury has followed.

Is it serious?

Discoria is not a disease in itself and may not have any effect on the patient’s health, but it can also be a sign caused by various conditions, from eye nerve damage caused by strokes to tumors or trauma.

Therefore, if a difference in pupil size is detected, it is imperative to urgently go to the ophthalmologist to rule out any risky situation.

In that case, an appointment should be made with the Department of Neuro-ophthalmology, in which all the necessary tests will be performed.

historical note

Around AD 200, Galen compared the iris to an elastic circular ring that was passively inflated or deflated by vital spirits sent from the brain to improve vision.

It was not until the first half of the 18th century that it was widely accepted that the movement of the iris and the size of the pupil were due to the active interaction of two muscles of the iris: a longitudinal radial dilator and a circular sphincter muscle.

Many contributions were made to our understanding of the physiology and pathology of the pupils in the 20th century, including the description of the oscillating lantern test to assess a relative afferent pupillary defect by Thompson in 2003.

Discoria Symptoms

If the size of the pupils is very uneven, a person may notice the discrepancy. More often, uneven pupils are noticed only during a medical exam.

The unequal pupils themselves usually cause no symptoms, but occasionally a person may have trouble focusing on nearby objects.

The main distinguishing feature of Discoria is a difference in the shape and size of the pupil or both pupils, such that the pupils differ between the two eyes.

In any given eye exam, up to 41% of healthy patients may show an anisocoria of 0.4 mm or more at one time or another. It can also happen since the difference between the two pupils varies from day to day.

A normal population survey showed that, in low light or near dark conditions, differences of 1 mm were found on average between the pupils.

The presence of Discoria has been estimated in 20% of the normal population, so a certain degree of pupil difference can be expected in at least 1 in 5 clinical patients.

These more noticeable symptoms are often the reason people seek medical attention. If you have no other symptoms, you can compare the size of your pupils with old photos of yourself to try to figure out when it happened.

This is rare, but it can be a sign of a bigger problem if the anisocoria just occurs or if the size of your two pupils is suddenly different for no reason.

Causes of Discoria

The pupil is an opening in the center of the iris through which light enters the eye. The size of the pupil can vary in response to the intensity of light and neurological stimuli.

Increased brightness causes pupillary constriction ( miosis ), while increased darkness causes pupillary dilation ( mydriasis ). Pupillary abnormalities can be caused by a variety of conditions.

Any disorder that physically damages the mechanical compliance of the iris or the iris musculature can result in an irregular pupil. Blunt trauma to the eye can cause focal tears in the sphincter muscle.

An iridodialysis occurs when the outer edge of the iris separates from its ciliary connection. Intraocular inflammation can damage the iris or cause it to adhere to the lens or cornea (synechiae).

Neovascularization can also distort the iris and alter pupillary reactivity. Iris malformation, such as coloboma and aniridia, will affect the size and function of the pupil.

The main cause of a deformed pupil in an adult is probably cataract surgery, but any surgical procedure in the anterior segment can have similar results.

To avoid unnecessary extensive neurological evaluation, it is essential to recognize these structural abnormalities of the iris as the cause of abnormal pupil size, shape, and reactivity.

When detected during childhood, without any other symptoms and when other disorders are ruled out through clinical testing, it should be considered a genetic or developmental phenomenon.

Asymmetric pupil or slag, potential causes of anisocoria, refer to an abnormal shape of the pupil that can occur due to developmental and intrauterine abnormalities.

There are many causes of pupillary abnormalities. Any process that affects the autonomic innervation of the iris muscles or damages the iris muscles itself will cause an abnormality in the pupil.

For example, a dorsolateral brain stem stroke can damage the central neuron of the oculosympathetic pathway to cause ipsilateral myiosis and poor pupillary dilation (Horner syndrome).

Miosis can also result from local trauma to the iris that causes mechanical restriction of pupillary movement.

Systemic autonomic neuropathies, such as diabetes mellitus, can denervate the iris sphincter muscle and cause a poor pupillary lumen reaction. A tonic pupil can also result from local inflammation of the ciliary ganglion.

The larger or smaller pupil may be abnormal depending on the cause.

Types of Discoria

Pupillary discoria can involve the afferent or efferent pathways. Anisocoria, where it is not physiological, indicates a problem with the efferent pupillary pathway, either parasympathetic or sympathetic.

Disorders of the parasympathetic system affect light response and include third nerve palsy and a tonic pupil. Iris disorders, including the application of cholinergic agents, should also be considered in the impaired pupillary light reaction.

There are several main types of abnormalities in the pupil (Discoria):

Unilateral

Uneven pupil size (anisocoria), irregular pupil shape, pupil displacement (corectopia), asymmetric pupillary reaction (relative afferent pupillary defect), and episodic abnormalities.

large unilateral pupil

This is a pupil that shows poor constriction in a well-lit room. Causes include:

  • Traumatic damage to the iris.
  • Third nerve palsy.
  • Rubeosis iridis (neovascular eye disease).
  • Holmes-Adie syndrome: can also be irregular, unusually one-sided.
  • Drug dilation (i.e. dilation drops).
Small unilateral pupil

This is a pupil that shows poor dilation in low light conditions. Causes include:

  • Physiologically small pupil.
  • Uveitis with synaechiae. Horner’s syndrome.
  • Argyll Robertson pupil (can also be irregular, usually bilateral).
  • Drug constriction (constriction of drops).

Bilateral

Poorly reactive to light with a good near response (near light dissociation), abnormal shape or position (corectopia), and change in size and reactivity.

The abnormality can be transient or constant. Pupillary abnormalities are often asymptomatic or observed by an observer.

Occasionally, patients complain of photophobia in an eye with a large pupil (mydriatic) because the increased light reaches the retina through the widest opening.

Because the parasympathetic system innervates the pupilloconstrictor and ciliary muscle to accommodate itself, patients with oculomotor nerve palsy or short ciliary nerve damage may report blurred near vision (such as while reading) in addition to the larger pupil size. .

Abnormal pupil shape

The human pupil must be round. Many other pupillary shapes are seen in nature, including vertical and horizontal slits, rectangles, and crescents.

A fixed oval pupil, associated with severe pain, red eye, cloudy cornea, and systemic discomfort, suggests acute angle-closure glaucoma.

Conditions that could be affecting the size or shape of the pupils

These are some of the reasons why the pupils can be different sizes or shapes.

Migraines

Dilated pupils can be a symptom of certain migraines. This specific type of severe headache is believed to cause abnormal paralysis of the motor nerves in the eye.

This not only causes persistent dilated pupils but the headache is focused around the eyes. Those who suffer also often complain of blurred vision.

Holmes-Adie syndrome

Holmes-Adie syndrome (JHS) is a neurological disorder in which one pupil is significantly larger than the other and contracts slowly under bright lights.

It is believed to be caused by a viral infection that causes inflammation and damage to the part of the brain that controls eye movement.

The condition generally progresses slowly in one eye before developing in the other. People with Holmes-Adie syndrome can also experience profuse sweating and it is more common in young women.

Horner syndrome

Horner syndrome is another neurological disease that can arise for a number of reasons, including tumors and medical treatments. The condition affects the sympathetic nervous system, which is responsible for the body’s fight or flight mechanism.

Horner is characterized by abnormally small pupils and can be accompanied by a droopy eyelid and bloodshot eyes. Decreased sweating on the affected side of the body is also common.

colobomas

A coloboma is a gap in one of the structures of the eye, and when it affects the iris it can make the pupil appear misshapen. Colobomas are most common in the lower half of the iris, giving the pupil a characteristic keyhole shape.

Colobomas are congenital, which means they are present from birth and are due to the baby’s eyes not developing properly during pregnancy.

The impact on your vision will depend on where the coloboma is located, although those in the iris generally have a limited effect on vision.

Iritis

When the iris becomes inflamed it is called iritis. The condition is classified as traumatic, due to an injury to the eye, or non-traumatic, which is usually due to infection or disease.

The most common symptoms include bloodshot eyes, eye pain, headaches, blurred vision, and small or misshapen pupils. You are also likely to experience pain when a bright light is shone on the affected eye.

Other underlying causes

Without visiting an optometrist, it is difficult to diagnose why you may have differently sized or irregularly shaped pupils. However, there are a number of more serious reasons for suffering from anisocoria. These include:

  • Brain abscess.
  • Tumor cerebral.
  • Meningitis.
  • Seizures
  • Aneurysms
  • Bleeding in the brain .

These are rare conditions, but it is important to seek medical help if you have anisocoria and want to rule it out.

Drugs that affect the pupils

Many drugs can affect the size of the pupil, both topically applied and generally ingested.

Such drugs can be drops to treat eye disorders (for example, homatropine used for certain inflammatory disorders or lesions or pilocarpine used for glaucoma).

Pointed pupils caused by opiate use are a barrier to evaluation of the brain-injured patient.

Topical mydriatics are widely used in ophthalmic practice to allow a complete examination of the eye.

Topical drugs

Dilation : sympathomimetics (such as phenylephrine, adrenaline (epinephrine)) and antimuscarinics (such as cyclopentolate, tropicamide, atropine).

Constriction : muscarinic agonists (such as Pilocarpine).

Systemic drugs

Dilation : sympathomimetics (such as Adrenaline (epinephrine)) and antimuscarinics (such as Atropine), tricyclic antidepressants, amphetamines, and ecstasy.

Constriction : opiates (such as morphine and organophosphates).

Discoria Diagnosis

The goal is to decide whether the larger or smaller pupil represents the problem. This refers to uneven pupils. Discoria is physiological (and harmless) in about 20% of people.

New-onset Discoria may suggest a serious underlying condition, such as Horner syndrome due to carotid dissection, or third nerve palsy due to an aneurysm.

It is necessary to first determine which pupil is behaving abnormally. Compare the pupils in dim and light conditions:

If there is a poor reaction (slow, partial, or absent) to light in one eye and the anisocoria is more evident in a well-lit room, the affected pupil is abnormally large.

If there is a good reaction to light in both eyes but poor, slow, or absent dilation in the dark (ie, the Discoria is enlarged), the affected pupil is abnormally small.

The variation between the eyes should not be more than 1 mm: both eyes should react to light normally. Normally, the pupils react (that is, they contract) in the same way.

Comparing the direct and consensual reaction to light in both eyes is useful to localize a lesion, remembering that the retina and optic nerve are necessary for the afferent signal and that the oculomotor nerve provides the efferent component of the direct and consensual reflexes. .

If the optic nerve of the first eye is damaged: the reflection of direct light is lost in the first eye, as is the consensual effect in the second eye, since it does not receive any message.

However, the oculomotor nerve in the first eye is intact, so your pupil will still contract when light shines into the other eye.

If the optic nerve of the second eye is damaged, when the light is shone on the first (normal) eye, the second eye will still show a consensual constriction, as its oculomotor nerve is intact.

If the oculomotor nerve in the first eye is damaged, it cannot produce a direct light reflection as the motor component is lost. However, the optic nerve still transmits the afferent signal, so the other eye will contract consensually to the light.

If the oculomotor nerve of the second eye is damaged, when the light is shone in the normal first eye, there is no consensual constriction of the second.

When to see a doctor

People with warning signs should see a doctor immediately. People without warning signs but who have other symptoms should call a doctor.

The doctor can decide how quickly they should be seen based on your symptoms.

What the doctor does

Doctors first ask questions about the person’s symptoms and medical history, including questions about smoking.

Doctors then do a physical exam. What they find during the history and physical examination often suggests a cause for the uneven pupils and the tests that need to be done.

Doctors ask if the person has recently had a head or eye injury, what eye drops the person has used, and if they have ever had an eye disorder or eye surgery.

Doctors examine the entire eye, usually using a slit lamp (an instrument that allows the doctor to examine the eye under high magnification). Other ocular symptoms are evaluated as necessary.

Doctors may use eye drops to test how the pupils respond to medications that cause the pupils to contract or widen.

Tests for Discoria

Testing is usually unnecessary unless people have other symptoms.

Pupil testing can reveal severe neuroophthalmic and retinal disease and should therefore be incorporated into every comprehensive eye exam.

With careful clinical examination, this test can aid in the diagnosis and management of many of these conditions at the primary care level.

The pupil examination is to the eye what deep tendon reflexes are to the neurological examination: objective, useful, and difficult to falsify. The “without fail” examination of the pupil includes:

Measurement of pupil size in light and dark, evaluation of the light reaction of the pupil in each eye, and the oscillating flashlight test to determine the presence of a relative afferent pupillary defect. If 1 or both pupils do not react well to light, more tests are done.

People with Horner syndrome or third cranial nerve palsy usually require magnetic resonance imaging (MRI) or computed tomography (CT). People who have Horner syndrome may also need a chest CT scan.

Discoria Treatment

The treatment of uneven pupils is in itself unnecessary. However, the underlying disorder may need to be treated.

As it is not a disease in itself, discoria may, in several cases, not need treatment.

However, the causes of this anomaly are extremely diverse and may require urgent attention, which is why it is necessary to urgently go to an ophthalmologist in case a different size of the pupils is detected. Therefore, treatment will depend on the cause.