Uneven Pupil Dilation

Dilation of the eyes refers to the expansion of the pupils. The pupil is the central, circular opening in the eyes, located in the iris that allows the passage of light in. The pupils dilate or enlarge whenever there is dim and low light, in order to allow more light to pass through.

Normally, the pupils of both eyes are the same size, however, in about 1 out of 5 people, there may be a difference in the size of the pupils, leading to uneven dilation.

While pupil dilation is a normal phenomenon, sometimes, the difference in the size of both pupils may be as wide as 0.4 mm or even larger.

This condition is called Anisocoria in medical terms and it could be brought on due to varied reasons. In this following story, we will understand what these causes are and go into more details about the same.

Physiological Anisocoria
About 20% of the populace is affected by this lifelong condition wherein the difference between the dilation is brought on as a normal variation, without a specific cause. The pupils are naturally different in size and both function just as effectively in both, light and darkness. 

In addition to which, there are no symptoms that are recorded.

Holmes Aide Syndrome
This is a neurological disorder affecting the pupil and the autonomic nervous system. It is caused by a viral or bacterial infection which affects an area of the brain responsible for eye movements. Holmes Aide Syndrome (HAS) is known to cause uneven pupil dilation.

Head Trauma
Accidents which cause head trauma are one of the most common reasons that lead to dilated pupils. In an accident, one of the visible signs of head injury is uneven pupil dilation and eye problems. If someone has uneven pupils brought on after an accident, it could be a cause for worry; the victim needs to be taken to the ER immediately.

Tumors
Brain tumors may sometimes be the underlying cause of uneven pupils, as the movement of the eyes is controlled by neurons in the ciliary ganglio, an area of the brain. If pupil dilation is caused by brain tumors, it is generally accompanied by migraines and severe headaches as well.

Nerve Damage
Nerves that run from the base of the brain to other parts of the brain are susceptible to damage by injury. These cranial nerves control our movements and the cranial nerves in the oculomotor, specifically the somatic motor, control the movements of the eyes. If these are damaged, they can cause dilated pupils.

Visiting a neurologist for treatment is a necessity in such cases.

Eye Medication
Certain eye drops can lead to the uneven dilation of pupils. The effect of this is usually temporary. These include allergy medication eye drops, as well as specialized eye drops used for eye inspections by ophthalmologists.

These can prompt one eye to dilate more than the other.

Plants
The Brugmansia Plant, commonly known as Angels Trumpet, is poisonous and can cause dilated pupils. This plant is found in parts of America like Florida and Georgia. Other plants like Deadly Nightshade which are natives to Asia, can also lead to uneven pupils.

It is important to note the following signs, which may be an indication of an underlying condition. If any of these signs are observed, and they are not a temporary phenomenon, it is imperative to visit an ophthalmologist immediately.

► Double vision
► Drooping eyelids
► Eye pain
► Redness in the eye
► Loss of vision

► Blurry vision
► Recent head or eye injury
► Headaches
► Stiff neck
► Increased sensitivity to light

Upon observation, the doctor will first determine the cause of the condition. For this, he will conduct a number of routine eye examinations and exercises. So also, the patient's medical history will also be studied. Though pupil dilation cannot be treated by itself, the underlying condition that has led to the same can be looked into and the treatment for the same can be administered. Which will then automatically correct the uneven pupil dilation.

Though certain conditions that lead to the uneven dilation of pupils may only be a temporary effect, there are certain other underlying conditions that may prove to be detrimental to the eye health and the overall health of a person. Which is why, it is imperative to consult a doctor if any of the warning signs are observed.

Disclaimer: The information provided in this story is solely for educating the reader. It is not intended to be a substitute for the advice of a medical expert.