Constricted pupils

Constricted Pupils

Constricted pupils, also known as miosis, refer to the condition where the pupils of the eye become smaller than normal. This physiological response can occur due to various factors, including exposure to bright light, certain medications, or underlying medical conditions.

Anatomy and Physiology

The pupil is the opening in the center of the iris that regulates the amount of light entering the retina. The size of the pupil is controlled by two sets of muscles: the sphincter pupillae, which constricts the pupil, and the dilator pupillae, which dilates it. The autonomic nervous system regulates these muscles, with the parasympathetic nervous system promoting constriction and the sympathetic nervous system promoting dilation.

Causes of Constricted Pupils

Physiological Causes

• Light Exposure: In bright light, the pupils constrict to reduce the amount of light entering the eye, protecting the retina from excessive light exposure.
• Accommodation Reflex: When focusing on a near object, the pupils constrict as part of the accommodation reflex to enhance depth of field and focus.

Pharmacological Causes

• Opioids: Drugs such as morphine and heroin can cause miosis as a side effect.
• Pilocarpine: This medication, used to treat glaucoma, can induce pupil constriction.

Pathological Causes

• Horner's Syndrome: A condition characterized by a triad of symptoms including ptosis, miosis, and anhidrosis due to disruption of sympathetic nerves.
• Brainstem Lesions: Damage to the brainstem can affect the pathways controlling pupil size, leading to miosis.

Diagnosis

Diagnosis of constricted pupils involves a thorough medical history and physical examination. The examination may include:

• Pupillary Light Reflex Test: Assessing the response of the pupils to light.
• Near Reflex Test: Evaluating the pupils' response to focusing on a near object.
• Pharmacological Testing: Using specific eye drops to determine the cause of miosis.

Treatment

Treatment of constricted pupils depends on the underlying cause. If due to medication, adjusting the dosage or switching drugs may be necessary. In cases of underlying medical conditions, treating the primary condition often resolves the miosis.

Also see

• Pupil
• Mydriasis
• Horner's Syndrome
• Autonomic Nervous System

External

• Age-Related Macular Degeneration

• Amblyopia (Lazy Eye)

• Anophthalmia and Microphthalmia

• Astigmatism

B

• Behçet's Disease* Bietti's Crystalline Dystrophy

• Blepharitis* Blepharospasm

C

• Cataracts

• Coloboma

• Color Blindness

• Corneal Conditions

D

• Diabetic Retinopathy

• Dry Eye

F

• Floaters

G

• Glaucoma

I

• Idiopathic Intracranial Hypertension

L

• Low Vision

M

• Macular Edema

• Macular Hole

• Macular Pucker

P

• Pink Eye

R

• Rare Diseases

• Refractive Errors

• Retinal Detachment

• Retinitis Pigmentosa

• Retinoblastoma

• Retinopathy of Prematurity

S

• Stargardt Disease

U

• Usher Syndrome

• Uveitis

V

• Vitreous Detachment