What is the cause and management of eye irritation and discharge in an elderly male patient taking ivermectin for scabies and using Clear Eyes (tetrahydrozoline) drops?

Eye Irritation with Discharge in Elderly Male on Ivermectin

Most Likely Diagnosis and Immediate Management

This patient most likely has blepharitis (eyelid margin inflammation) or medication-induced keratoconjunctivitis from the tetrahydrozoline drops (Clear Eyes), and should immediately discontinue the vasoconstrictor drops and start preservative-free artificial tears 4 times daily. 1

The temporal relationship with ivermectin initiation raises concern for Demodex blepharitis, as scabies patients often have concurrent Demodex infestation, and the morning discharge with crusting is characteristic of blepharitis rather than simple conjunctivitis. 1

Critical First Step: Stop the Clear Eyes Drops

• Tetrahydrozoline (Clear Eyes) is a vasoconstrictor that causes rebound hyperemia (conjunctivitis medicamentosa) with prolonged use beyond 10 days, which can worsen the underlying condition and create a cycle of worsening symptoms. 2
• The patient has been using these drops for two weeks, which exceeds the safe duration and likely contributes to ongoing irritation. 2

Recommended Treatment Algorithm

Step 1: Initial Management (Start Immediately)

• Prescribe preservative-free artificial tears (lipid-based formulation preferred) 4 times daily to address tear film instability common in blepharitis patients. 1
• Initiate warm compresses to eyelids twice daily for 5-10 minutes followed by gentle eyelid margin cleansing to address meibomian gland dysfunction. 1
• Store artificial tears in refrigerator for additional cooling relief upon instillation. 2

Step 2: If No Improvement in 48-72 Hours

• Add olopatadine 0.1% ophthalmic solution twice daily as a dual-action antihistamine/mast cell stabilizer, which addresses both allergic and inflammatory components. 2, 3
• Continue preservative-free artificial tears and eyelid hygiene. 1

Step 3: If Symptoms Persist After 1-2 Weeks

Consider Demodex blepharitis given the scabies history and ivermectin use:

• Topical ivermectin cream 1% applied weekly to eyelid margins has been shown to significantly improve symptoms, ocular surface staining, eyelid debris, redness/swelling, and telangiectasias compared with eyelid hygiene alone. 1
• Alternative: Tea tree oil 50% eyelid scrubs weekly plus daily tea-tree-oil shampoo scrubs for minimum 6 weeks, though caution is needed regarding corneal epithelial toxicity at concentrations exceeding recommended levels. 1
• FDA-approved option: Lotilaner ophthalmic solution 0.25% twice daily for 6 weeks, which significantly reduces collarettes, decreases or eradicates mites, and reduces eyelid erythema. 1

Step 4: For Severe or Refractory Cases

• Brief course (1-2 weeks maximum) of loteprednol etabonate or fluorometholone for severe inflammation, with mandatory baseline and periodic intraocular pressure monitoring. 1, 2
• Oral doxycycline 50-100 mg daily if posterior blepharitis with meibomian gland dysfunction is prominent, as tetracyclines decrease lipase production and have anti-inflammatory properties. 1

Important Clinical Pearls

Why Ivermectin Connection Matters

• Oral ivermectin (taken for scabies) has been reported to benefit recalcitrant Demodex blepharitis, suggesting the patient may have concurrent Demodex infestation that could improve with continued systemic ivermectin therapy. 1
• Studies show topical and systemic ivermectin successfully reduce or eliminate D. folliculorum in epilated lashes of patients with blepharitis. 1
• The timing suggests this may be pre-existing Demodex blepharitis becoming apparent, rather than a side effect of ivermectin. 1

Critical Pitfalls to Avoid

• Never use punctal plugs in this patient, as they would prevent flushing of inflammatory mediators and debris from the ocular surface. 2
• Avoid topical antibiotics unless clear bacterial infection is present, as they provide no benefit for blepharitis, induce toxicity, and contribute to antibiotic resistance. 2
• Do not continue vasoconstrictor drops (Clear Eyes), as prolonged use beyond 10 days causes rebound vasodilation and worsens symptoms. 2
• If prescribing corticosteroids, strictly limit to 1-2 weeks maximum with mandatory intraocular pressure monitoring due to risks of glaucoma and cataract formation. 1, 2

Monitoring Requirements

• Reassess at 2 weeks to evaluate treatment response and adjust therapy accordingly. 1
• If corticosteroids are used, perform baseline intraocular pressure measurement and pupillary dilation to evaluate for glaucoma and cataract, with periodic monitoring throughout treatment. 2
• Monitor for corneal complications if using tea tree oil preparations, as concentrations exceeding 50% can cause corneal epithelial defects. 1

Red Flags Requiring Urgent Ophthalmology Referral

• Development of vision changes, severe pain, or photophobia. 1
• Unilateral presentation with nodular mass, ulceration, extensive scarring, or localized crusting (concern for eyelid malignancy such as sebaceous carcinoma). 1
• Persistent epithelial defect or corneal ulceration. 1, 4
• No improvement after 4 weeks of appropriate therapy. 1