-
DE
Miosis: Pupil Constriction – Causes & Treatment
Miosis is the constriction of the pupil of the eye to a diameter of less than 2 mm. It can occur naturally in bright light or be caused by medications, drugs, or neurological conditions.
Add as Preferred SourceThings worth knowing about "Miosis"
Miosis is the constriction of the pupil of the eye to a diameter of less than 2 mm. It can occur naturally in bright light or be caused by medications, drugs, or neurological conditions.
What is Miosis?
Miosis refers to the constriction (narrowing) of the pupil to a diameter of less than 2 mm. The size of the pupil is controlled by two muscles within the iris: the sphincter pupillae muscle, which constricts the pupil, and the dilator pupillae muscle, which widens it. Miosis occurs when the sphincter muscle dominates. It can be physiological (normal), pharmacological (caused by drugs or medications), or pathological (caused by disease).
Causes
Physiological Causes
- Light exposure: The most common cause of miosis is increased light intensity. The pupillary light reflex automatically constricts the pupil in bright light to protect the retina.
- Near response (accommodation): When focusing on close objects, the pupil also constricts as part of the accommodation reflex.
- Aging: In older adults, a physiological miosis known as senile miosis may occur due to age-related changes in iris muscles.
Pharmacological Causes
- Opioid analgesics (e.g., morphine, heroin): These substances activate the parasympathetic nervous system and produce characteristic pinpoint pupils.
- Miotic eye drops (e.g., pilocarpine): Used in the treatment of glaucoma to lower intraocular pressure.
- Cholinergic agents and anticholinesterase inhibitors (e.g., organophosphates, physostigmine).
- Antipsychotics and certain antidepressants.
Pathological Causes
- Horner syndrome: Damage to the sympathetic nerve pathway leads to miosis, drooping of the upper eyelid (ptosis), and sinking of the eyeball (enophthalmos) on the affected side.
- Pontine lesions: Hemorrhages or infarcts in the brainstem (pons) can cause bilateral, pronounced miosis.
- Iritis / Uveitis: Inflammation in the anterior segment of the eye can reflexively trigger miosis.
- Organophosphate poisoning (pesticides, nerve agents): A classic sign of a cholinergic crisis.
Symptoms and Clinical Presentation
Miosis itself is a clinical sign, not a standalone disease. The pupil appears very small and may respond less strongly to light stimuli. Associated symptoms depend on the underlying cause and may include:
- Blurred vision or reduced contrast sensitivity in low-light conditions
- Ptosis (drooping of the upper eyelid) in Horner syndrome
- Pain, redness, or photophobia in inflammatory causes
- Neurological symptoms in brainstem lesions (dizziness, double vision, swallowing difficulties)
- Altered consciousness in opioid intoxication
Diagnosis
Miosis is diagnosed through a clinical examination of the eye, which typically includes:
- Pupillometry: Assessment of pupil size and symmetry (isocoria vs. anisocoria).
- Pupillary reflex testing: Evaluation of the direct and consensual light response.
- Slit-lamp examination: Assessment of the anterior eye segment for signs of inflammation.
- Neurological examination: Performed when a central cause is suspected (brainstem lesion, Horner syndrome).
- Imaging (MRI/CT): In cases of suspected cerebral or vascular causes.
- Toxicological screening: When poisoning or drug use is suspected.
Treatment
Treatment is directed at the underlying cause of miosis:
- Pharmacological miosis due to opioid overdose: Administration of naloxone as an antidote.
- Organophosphate poisoning: Treatment with atropine and pralidoxime.
- Horner syndrome: Management of the underlying condition (e.g., tumor, vascular injury).
- Iritis/Uveitis: Topical corticosteroids and mydriatic eye drops (pupil-dilating agents).
- Glaucoma-related miosis from pilocarpine: A desired therapeutic effect to reduce intraocular pressure.
References
- Kanski, J. J. & Bowling, B. (2016). Clinical Ophthalmology: A Systematic Approach. Elsevier.
- Bhatti, M. T. & Bhatti, A. (2017). Pupillary disorders: Diagnostic approach. Seminars in Neurology, 37(5), 508–518. PubMed PMID: 29207412.
- World Health Organization (WHO) (2022). Management of substance abuse: Opioid overdose. Retrieved from https://www.who.int/substance_abuse/information-sheet/en/
Building Blocks for a Healthy Life
As an integrated manufacturer, we develop & produce evidence-based, patented, and non-patented formulations. We work exclusively with plant and natural extracts according to the strictest purity & quality standards.
The combination of science & modern technology with the laws of nature creates solutions consistently tailored to humans – for the highest good: health.
Skip product gallery
Subscription available
Floral
For Healthy Oral Flora & Dental Care
Formulated lozenges with Dentalac®, lactic acid bacteria, and Lactoferrin CLN®30 lozenges
Regular price:
22,90 €
Discount
Subscription available
Lactoferrin 60 Capsules
For your universal protection
As one of the most valuable proteins in the body, lactoferrin is a natural component of the immune system.
60 Capsules
Sale price:
50,00 €
Regular price:
59,90 €
Discount
Subscription available
Multivitamin Mineral Complex
Daily basic supply: the complete spectrum of micronutrients
Natural multivitamin complex for the immune system, energy, and central body functions
30 Capsules
Sale price:
27,90 €
Regular price:
29,90 €
Subscription available
Natural Iron
For your iron balance
Specially formulated for your iron balance with plant-based curry leaf iron, Lactoferrin CLN®, and natural Vitamin C from rose hips.
30 Capsules
Regular price:
35,90 €
Most read entries
3 Posts in this encyclopedia categoryMagnesiumcarbonat
Magnesiumcarbonat ist eine anorganische Magnesiumverbindung mit säure-neutralisierender (antazidischer) Wirkung. Erfahre mehr über Vorteile, Einsatzgebiete und Unterschiede zu besser resorbierbaren Magnesiumformen.
Calorie content
The choice of food influences our energy intake. The calorie content varies greatly - some provide little energy, others a lot.
Cologne list
The Cologne List ® is an important initiative in competitive sports that offers athletes guidance in the selection of nutritional supplements.