Understanding Drug-Induced Glaucoma
Drug-induced glaucoma is a form of secondary glaucoma that arises as an adverse effect of certain medications. This condition can manifest as either open-angle glaucoma or the more acute angle-closure glaucoma. Both forms can lead to increased intraocular pressure (IOP), potentially causing optic nerve damage and vision loss if not managed. Awareness of medications that can cause this reaction and understanding their mechanisms are crucial for prevention.
Corticosteroids and Open-Angle Glaucoma
Corticosteroids are frequently implicated in medication-induced glaucoma, typically the open-angle type. The risk of elevated IOP from steroids is influenced by factors like potency, dosage, duration, and individual susceptibility. Steroid-induced ocular hypertension occurs due to increased resistance to aqueous humor outflow at the trabecular meshwork.
This can happen through various routes:
- Topical drops: Eye drops (e.g., dexamethasone, prednisolone) for conditions like uveitis or allergic conjunctivitis are a common cause.
- Systemic use: Oral or intravenous steroids used for widespread inflammatory conditions can increase IOP.
- Inhaled and nasal sprays: Used for asthma and allergies, these carry a lower risk than topical or systemic routes.
- Dermatological creams: Steroid creams applied to eyelids can raise eye pressure, especially with long-term use.
Medications Causing Acute Angle-Closure Glaucoma
Acute angle-closure glaucoma (AACG) triggered by medication is an urgent condition requiring immediate medical attention. Certain drugs can cause AACG in individuals with anatomically narrow drainage angles. The main mechanism is pupillary dilation (mydriasis), where the iris blocks the trabecular meshwork, preventing aqueous humor drainage.
Medication classes that can cause AACG via pupillary block include:
- Anticholinergics: Found in some antihistamines, cold remedies, and medications for incontinence and motion sickness.
- Adrenergic agonists: Sympathomimetic drugs in decongestants (e.g., phenylephrine, pseudoephedrine) can dilate the pupil.
- Certain Antidepressants: Tricyclic antidepressants and some SSRIs have weak anticholinergic effects that increase risk in susceptible patients.
- Botulinum Toxin: Injections near the eyes can cause pupillary dilation.
Sulfa Drugs and Idiosyncratic Angle Closure
An idiosyncratic reaction to certain sulfa-based medications can cause a distinct and severe type of AACG. This reaction doesn't depend on pre-existing narrow angles and involves a forward displacement of the iris-lens diaphragm due to ciliary body swelling and choroidal effusion. This bilateral condition often occurs soon after starting the medication and is accompanied by acute myopia, blurred vision, and eye pain.
A notable example is the medication topiramate (Topamax). Other sulfa-containing drugs, like some antibiotics (trimethoprim-sulfamethoxazole) and diuretics (acetazolamide, hydrochlorothiazide), can also cause this reaction. Treatment involves immediately stopping the medication and using specific eyedrops, as standard angle-closure treatments may be ineffective or harmful.
Comparison of Medication-Induced Glaucoma Types
| Feature | Steroid-Induced Open-Angle Glaucoma | Drug-Induced Acute Angle-Closure Glaucoma | Sulfa-Induced Acute Angle-Closure Glaucoma |
|---|---|---|---|
| Onset | Gradual (weeks to months) | Rapid (hours to days) | Rapid (days to weeks) |
| Mechanism | Increased resistance to aqueous outflow in the trabecular meshwork | Pupillary block from mydriasis in a narrow-angle eye | Ciliary body swelling and choroidal effusion causing anterior lens displacement |
| Affected Eye(s) | Can be unilateral or bilateral, depending on administration | Typically unilateral, unless both eyes have narrow angles | Usually bilateral |
| Associated Symptoms | Often asymptomatic until advanced damage; may have blurred vision | Severe eye pain, headache, nausea, blurred vision, halos | Acute myopia (nearsightedness), blurred vision, eye pain, headache |
| Predisposing Factors | Pre-existing glaucoma, family history, high myopia, diabetes | Narrow anterior chamber angles, farsightedness, female, Asian ethnicity | Idiosyncratic reaction; can occur in eyes with open or narrow angles |
| Example Medications | Dexamethasone, Prednisolone | Antihistamines, Antidepressants, Decongestants | Topiramate, Trimethoprim-sulfamethoxazole |
| Management | Discontinue steroid if possible; use IOP-lowering medication; laser or surgery if needed | Discontinue drug; use IOP-lowering medication; laser peripheral iridotomy may be needed | Discontinue drug; use cycloplegics and IOP-lowering medication; laser iridotomy is ineffective |
Communicating with Your Healthcare Team
Patients should provide their ophthalmologist with a complete list of all medications, including over-the-counter drugs, supplements, and eyedrops. Any new medication or changes in vision, eye pain, or other symptoms should be reported promptly. For those at high risk for glaucoma, such as individuals with narrow angles or a family history, prophylactic laser iridotomy might be considered before starting certain medications. Timely identification and communication are vital for preventing vision loss from medication-induced glaucoma.
Conclusion
Medication-induced glaucoma is a serious condition, though relatively uncommon. Both patients and physicians must be vigilant. The condition can range from the gradual open-angle changes caused by corticosteroids to the acute emergencies triggered by anticholinergics and sulfa drugs, with varying mechanisms and risk factors. Proactive steps, including a comprehensive medication history and monitoring for high-risk patients, are crucial. The best prevention involves informing your healthcare providers about all medications to ensure a safe treatment plan that protects your ocular health.
