What ophthalmic side effects can chlorthalidone cause?

Ophthalmic Side Effects of Chlorthalidone

Chlorthalidone can cause acute bilateral angle-closure glaucoma with uveal effusions and acute myopia, typically occurring within the first week of treatment—this is a rare but serious idiosyncratic reaction requiring immediate drug cessation. 1, 2

Primary Ocular Adverse Effects

Acute Angle-Closure Glaucoma with Uveal Effusions

• Chlorthalidone induces bilateral ciliochoroidal effusions that mechanically push the lens-iris diaphragm forward, causing appositional angle closure and elevated intraocular pressure. 1
• This reaction typically manifests within 1 week of initiating chlorthalidone therapy. 1
• Clinical presentation includes:
  • Bilateral shallow anterior chambers 1
  • Elevated intraocular pressure 1
  • Acute myopic shift (sudden worsening of distance vision) 1, 2
  • Suspected ciliary body edema on ultrasound examination 1

Acute Myopia

• Sudden development of myopia occurs due to ciliary spasm and forward displacement of the lens-iris diaphragm from choroidal effusions. 2
• Associated findings include:
  • Shallow peripheral choroidal effusion 2
  • Retinal striae at the macula 2
  • Increased macular thickness on optical coherence tomography 2
• This represents a transient refractive change distinct from the chronic myopia seen with other medications. 3

Management of Chlorthalidone-Induced Ocular Reactions

Immediate Intervention

• Discontinue chlorthalidone immediately upon recognition of angle-closure or acute myopia. 1, 2
• Administer cycloplegics to relax ciliary spasm and deepen the anterior chamber. 1
• Use ocular antihypertensives to control intraocular pressure acutely. 1

Expected Resolution

• Complete reversal of all ocular findings occurs promptly after drug cessation—including normalization of anterior chamber depth, intraocular pressure, refractive error, and choroidal effusions. 1, 2
• Macular thickness and retinal striae resolve completely once the drug is withdrawn. 2

Additional Ocular Considerations from FDA Labeling

The FDA drug label for chlorthalidone does not specifically list ophthalmic adverse reactions in its adverse reactions section, focusing instead on systemic effects (gastrointestinal, CNS, hematologic, dermatologic, cardiovascular, and metabolic reactions). 4 However, the case reports establish a clear causal relationship for the acute angle-closure and myopia syndrome.

Clinical Pitfalls and Monitoring

Key Warning Signs

• Any patient reporting sudden bilateral blurred vision or eye pain within the first 1-2 weeks of starting chlorthalidone should be evaluated emergently for angle-closure glaucoma. 1, 2
• Unlike anticholinergic-induced angle closure (which occurs in predisposed narrow-angle patients), chlorthalidone causes a unique mechanism via uveal effusions that can affect patients without pre-existing narrow angles. 1

Distinction from Other Drug-Induced Angle Closure

• Thiazide diuretics as a class can cause transient refractive changes 3, but chlorthalidone's specific mechanism of bilateral uveal effusions with angle closure is an idiosyncratic reaction distinct from the pupillary block mechanism seen with anticholinergic agents. 1
• This reaction is not dose-dependent and represents an allergic-type hypersensitivity response. 1

Patient Education

• Warn patients starting chlorthalidone to report immediately any sudden vision changes, eye pain, or seeing halos around lights—particularly in the first week of therapy. 1, 2
• Emphasize that this is a reversible condition if recognized early and the medication is stopped. 1, 2