Normally, both pupils are the same size and are round in shape. However when it happens pupillary abnormalities, size between the right and left pupils may not be the same and the shape can change. Abnormalities in the pupil need to be recognized, because it can signal a dangerous condition.
The pupil is the part in the center of the eye that is round and black in color. The function of the pupil is to regulate how much light enters the eye.
To perform its function, the pupil will dilate when you are in a dark place, to capture more light. Conversely, the pupil will shrink when you are in a brighter place or when the eye is exposed to bright light. In addition to being affected by light, both pupils usually shrink when the eye is focused on close objects.
Various Abnormalities in the Eye Pupil
Under light conditions, the normal pupil of an adult eye will be 2-4 mm in diameter. Whereas in dark conditions, the pupil will dilate to 4-8 mm. The pupils in both eyes are normally the same size.
However, if there is an abnormality of the pupil of the eye, the size of the two pupils can be not the same. Pupillary abnormalities can also cause the pupil to not dilate when it's dark and not shrink when it's bright or when looking at objects up close.
The following are some abnormalities that can occur in the pupil of the eye:
Different pupil size
Anisocoria is a condition in which the pupil size of the right and left eyes differs greatly, up to more than 3-5 mm. This condition is nothing to worry about if you were born with this condition or do not experience other disturbing complaints.
However, if the pupil size of the eye suddenly becomes unequal, can't return to its original size, or is accompanied by visual disturbances, it's likely anisocoria it is caused by certain medical conditions, such as:
- Impact or injury to the eye.
- Bleeding in the brain.
- Brain injury.
- Convulsions.
- Migraine.
- Glaucoma.
- Increased pressure inside the head, for example due to a brain tumor.
- Brain infections, such as brain abscess, meningitis, and encephalitis.
- Stroke or paralysis of the optic nerve.
In addition to disease, pupil dilation or shrinkage to unequal size can also be caused by organophosphate poisoning or side effects of drugs, such as:
- Asthma medicine.
- Certain narcotics, for example methadone, heroin and morphine.
- Atropine.
- Adrenaline or epinephrine.
The shape of the pupil of the eye is not round
The pupil of the human eye should be perfectly round. However, in pupillary abnormalities, the shape can change to be rectangular, elongate vertically or horizontally, or look like a crescent moon.
This abnormal pupil shape can be caused by congenital abnormalities, eye injury, Horner's syndrome, adhesions between the iris (the colored part of the eye) and the lens of the eye, or in patients who have recently had cataract surgery.
The pupil of the eye does not react to light
Normally, the pupil of the eye reacts to light by dilating when it is in the dark, or shrinking when it is exposed to light. In people who have pupillary abnormalities, the light reflex in the pupil of the eye will not occur.
Loss of light reflex in the pupil of the eye can be caused by several things, such as:
- Injury or impact on the eye.
- Brain injury.
- Brain hemorrhage, for example due to a brain aneurysm or hemorrhagic stroke.
- Brainstem death, which can also be considered a sign of death.
Indeed, pupillary abnormalities are not always dangerous, especially if they are not accompanied by other complaints or diseases. However, you need to be careful if your pupil sizes are not the same, accompanied by sudden blurred or blind vision, double or ghosting vision, easy glare, eye pain, watery and red eyes, and headaches.
If abnormalities in the pupil of the eye are accompanied by these symptoms, you should immediately consult an ophthalmologist to determine the cause and get treatment.