What is the treatment for ocular parasitism (worms in the eyes)?

Treatment of Ocular Parasitism (Worms in the Eyes)

Surgical removal of the visible worm is the definitive treatment for intraocular parasites, followed by species-specific antiparasitic therapy and corticosteroids to prevent inflammatory damage. 1

Immediate Management Algorithm

Step 1: Emergency Ophthalmologic Consultation

• All cases of suspected ocular parasitism require immediate ophthalmologic intervention to prevent irreversible vision loss 2, 1
• Perform indirect funduscopic examination, which is more sensitive than direct examination for detecting intraocular parasites 2
• Obtain ocular ultrasound if direct visualization is inadequate 2
• Document the exact location of the parasite (anterior chamber, vitreous, subconjunctival, or retinal) 1, 3

Step 2: Surgical Extraction When Feasible

• For visible worms in the anterior chamber or subconjunctival space, immediate surgical removal is the treatment of choice 4, 5
• Incise overlying conjunctiva and extract the worm intact to confirm species identification 4
• For intraocular worms causing endophthalmitis, perform diagnostic vitreous tap followed by pars plana vitrectomy with intravitreal amphotericin B (10 mg dose) 2, 6, 1
• Vitrectomy removes inflammatory debris and infectious organisms, which is sight-saving 2, 6

Species-Specific Antiparasitic Therapy

For Loa loa (Most Common Cause of Visible Eye Worms)

• Administer diethylcarbamazine after surgical removal 4
• This is the most frequently reported cause of visible worms migrating across the eye in travelers from west and central Africa 4, 3
• Obtain thick blood films for microfilariae and filarial serology 4

For Ocular Toxocariasis

• Albendazole 400 mg twice daily for 2 weeks combined with corticosteroids 1
• Corticosteroids are essential to control the inflammatory response that can cause more damage than the parasite itself 1
• Consider intravitreal injections or vitrectomy for significant vitreous involvement 1
• Monitor for hepatotoxicity and leukopenia if treatment exceeds 14 days 2

For Neurocysticercosis with Ocular Involvement

• CRITICAL PITFALL: Do NOT give albendazole or praziquantel if intraocular cysts are present 2
• Antiparasitic agents can cause death of the parasite and trigger severe inflammatory reactions leading to permanent retinal damage 7
• Screen all neurocysticercosis patients for retinal lesions with indirect funduscopy before initiating systemic antiparasitic therapy 2
• If retinal lesions are visualized, weigh the need for anticysticeral therapy against the risk of retinal damage 7

For Onchocerciasis

• Doxycycline 200 mg once daily for 6 weeks to target symbiotic Wolbachia 1
• Ivermectin 200 μg/kg monthly for 3 months starting on day one of doxycycline 1

For Thelaziasis (Eyeworm)

• Mechanical removal of the worm from the conjunctival sac is curative 8
• No systemic antiparasitic therapy is typically required after complete removal 8

Adjunctive Anti-Inflammatory Therapy

Corticosteroid Regimens

• Systemic corticosteroids are mandatory when treating intraocular parasites with antiparasitic drugs to prevent inflammatory damage from dying parasites 1, 7
• Dexamethasone 0.1 mg/kg/day for the duration of antiparasitic therapy, OR 2
• Prednisone 1-2 mg/kg/day during therapy 2
• For neurocysticercosis patients, higher doses (dexamethasone 8 mg/day for 28 days with taper) reduce seizure risk 2

Anticonvulsant Therapy

• Patients with neurocysticercosis should receive anticonvulsant therapy to prevent seizures from inflammatory reactions 7
• Continue anticonvulsants until resolution of enhancing lesions on imaging 2

Treatment for Parasitic Endophthalmitis

Primary Therapy

• Intravenous amphotericin B plus intravitreal amphotericin B (10 mg dose) with pars plana vitrectomy 2, 6, 1
• Voriconazole (intravitreal or systemic) is an alternative regimen 2, 6, 1
• Treatment duration should continue for at least 4-6 weeks depending on resolution of lesions 6

Important Considerations

• Amphotericin B penetration into vitreous and aqueous humor is inadequate with systemic administration alone, necessitating intravitreal injection 2
• Direct macular involvement is a poor prognostic indicator for visual acuity recovery 2, 6
• Subconjunctival injections alone are ineffective and should not replace intravitreal administration 6

Critical Pitfalls to Avoid

1. Never administer systemic antiparasitic drugs before ruling out intraocular cysts in neurocysticercosis patients, as this can cause irreversible blindness 2, 7

2. Do not use antiparasitic agents in patients with increased intracranial pressure from diffuse cerebral edema or untreated hydrocephalus, as they worsen cerebral edema 2

3. Always combine antiparasitic therapy with corticosteroids when treating intraocular parasites to prevent inflammatory damage 1, 7

4. Obtain species identification whenever possible through surgical extraction, as treatment varies significantly by parasite type 1, 4, 3

5. Monitor for bone marrow suppression with albendazole therapy lasting >14 days by checking blood counts every 2 weeks 2, 7

6. Check liver enzymes before each treatment cycle and every 2 weeks during albendazole therapy, discontinuing if levels exceed twice the upper limit of normal 7

Geographic and Epidemiologic Clues

• Travel to west and central Africa suggests Loa loa 4, 3
• Rural areas in China with dog exposure suggest Thelaziasis 8
• Contact with contaminated soil or infected puppies indicates toxocariasis 1
• Consumption of undercooked meat or shellfish suggests toxoplasmosis 1
• Proximity to fast-flowing rivers in sub-Saharan Africa, Yemen, or South America suggests onchocerciasis 1