What is the treatment for constricted pupils (miosis)?

Treatment of Constricted Pupils (Miosis)

The treatment for constricted pupils (miosis) depends on the underlying cause, with medical therapy typically initiated first to address the condition, followed by definitive treatment such as laser iridotomy in cases of angle closure.

Causes and Evaluation of Miosis

Before initiating treatment, it's essential to identify the underlying cause of miosis:

1. Angle-closure related miosis:

   • Primary angle-closure disease
   • Acute angle-closure crisis (AACC)
   • Pupillary block

2. Drug-induced miosis:

   • Opioid use 1, 2
   • Topical medications

3. Neurological causes:

   • Horner's syndrome
   • Cluster headache 3

Treatment Algorithm for Miosis

1. For Angle-Closure Related Miosis

A. Acute Angle-Closure Crisis (AACC)

This is a medical emergency requiring immediate intervention to prevent vision loss.

1. Initial Medical Therapy 4:

   • Topical beta-adrenergic antagonists
   • Topical alpha2-adrenergic agonists
   • Topical, oral, or intravenous carbonic anhydrase inhibitors
   • Oral or intravenous hyperosmotic agents

2. Important Note: While parasympathomimetics (miotics like pilocarpine) are typically used for glaucoma, they may be ineffective in AACC when IOP is markedly elevated due to pressure-induced ischemia of the pupillary sphincter 4.

3. Definitive Treatment:

   • Laser iridotomy is the preferred surgical treatment due to its favorable risk-benefit ratio 4
   • Performed as soon as corneal edema clears
   • Relieves pupillary block and prevents peripheral anterior synechiae formation

4. Alternative Approaches when laser iridotomy isn't possible:

   • Corneal indentation with gonioscopic lens or cotton-tipped applicator
   • Anterior chamber paracentesis
   • Incisional iridectomy
   • Peripheral laser iridoplasty

B. Chronic Angle-Closure Glaucoma

After addressing pupillary block:

• Additional IOP-lowering therapy similar to open-angle glaucoma
• Consider lens extraction, which can significantly widen the anterior chamber angle 4

2. For Drug-Induced Miosis

A. Opioid-Induced Miosis

• Discontinue or reduce opioid dose if possible
• Pupil diameter typically remains between 2-3mm even with significant opioid toxicity 2
• The pupillary light reflex remains quantifiable even during opioid-induced respiratory depression 2

B. Medication-Related Miosis

• Identify and discontinue the causative agent
• Consider temporary use of mydriatic agents if clinically indicated

3. For Neurological Causes

A. Horner's Syndrome

• Diagnostic testing with apraclonidine 1% can help confirm diagnosis 5
• Treatment targets the underlying cause (tumor, stroke, etc.)

B. Cluster Headache

• Treat the underlying headache condition
• Note that there may be unilateral impairment of pupillary response on the affected side 3

Special Considerations

1. Mydriatics vs. Miotics: In cases of secondary pupillary block due to intraocular gas, oil, vitreous, or lens-related issues, mydriatics may be more effective than miotics 4.

2. Pilocarpine: While useful in open-angle glaucoma, pilocarpine can also be used in acute closed-angle glaucoma, often in combination with other agents to relieve pressure prior to emergency surgery 6.

3. Timing of Assessment: When using diagnostic agents like apraclonidine, the effect is most pronounced 30-60 minutes after instillation 5.

Pitfalls to Avoid

1. Don't delay definitive treatment in acute angle-closure - laser iridotomy should be performed as soon as possible after initial medical therapy 4.

2. Don't assume all miosis requires dilation - treatment should target the underlying cause rather than simply reversing the miosis.

3. Don't miss secondary causes of angle closure that may persist after iridotomy, such as plateau iris syndrome or phacomorphic angle closure 4.

4. Don't overlook the fellow eye in cases of angle-closure, as it is at high risk for a similar event and should receive prophylactic laser iridotomy if anatomically narrow 4.