What is the treatment for parasitic infections in the eyes?

Treatment of Parasitic Eye Infections

For parasitic eye infections, treatment depends critically on the specific parasite and location of infection, with ocular toxocariasis requiring albendazole 400 mg twice daily for 2 weeks plus corticosteroids under joint ophthalmology management, while onchocerciasis demands urgent ophthalmology assessment and doxycycline 200 mg daily for 6 weeks plus ivermectin. 1, 2

Initial Assessment and Diagnosis

Before initiating any antiparasitic therapy, perform these critical steps:

• Obtain indirect funduscopic examination or ocular ultrasound to screen for intraocular parasites, particularly in neurocysticercosis cases where retinal involvement contraindicates treatment 2, 3
• Examine for retinal lesions before starting therapy, as albendazole-induced parasite death can cause inflammatory retinal damage 3
• Obtain pregnancy testing in females of reproductive potential prior to albendazole therapy 3
• Monitor baseline blood counts and liver enzymes before treatment initiation 3

Treatment by Specific Parasite

Ocular Toxocariasis (Toxocara canis/cati)

Primary regimen:

• Albendazole 400 mg orally twice daily for 2 weeks 1
• Concurrent corticosteroids to control inflammation 1
• Mandatory joint management with ophthalmology 1

For complicated cases with vitreous involvement:

• Consider intravitreal injections similar to fungal endophthalmitis management 1
• Vitrectomy may be necessary for significant vitreous opacity 1

Critical caveat: Ocular toxocariasis often presents without systemic eosinophilia, making diagnosis challenging 1, 4

Onchocerciasis (River Blindness)

This requires urgent ophthalmology assessment due to risk of blindness 2

Before treatment:

• Exclude loiasis co-infection - seek expert advice if present 2
• Perform slit lamp examination for microfilariae 2

Treatment protocol:

• Doxycycline 200 mg orally once daily for 6 weeks (targets symbiotic Wolbachia) 2
• Starting day 1 of doxycycline: Ivermectin 200 μg/kg orally monthly for 3 months 2
• Continue ivermectin every 3-6 months until asymptomatic, then annually for several years 2, 5

Clinical presentation includes: severe pruritus, skin depigmentation, keratitis, uveitis, and choroidoretinitis 2

Cutaneous Larva Migrans (Eye Involvement)

• Ivermectin 200 μg/kg orally as single dose OR albendazole 400 mg orally once daily for 3 days 2
• Presents with characteristic serpiginous rash migrating 1-2 cm per day 2

Lymphatic Filariasis with Ocular Involvement

Critical pre-treatment step:

• Exclude onchocerciasis and loiasis if patient traveled to co-endemic areas 2

Treatment:

• Diethylcarbamazine (DEC) 6 mg/kg orally in 3 divided doses 2
• Specialist input strongly advised 2

Toxoplasmosis Retinochoroiditis

While specific treatment protocols are not detailed in the provided guidelines, this is noted as one of the most common parasitic ocular infections, particularly in travelers to Central and South America where more virulent genotypes exist 2. Requires long-term monitoring due to high recurrence risk 2.

Fungal Endophthalmitis (For Comparison/Differential)

Since fungal infections can mimic parasitic disease:

For Aspergillus endophthalmitis:

• Intravenous amphotericin B PLUS intravitreal amphotericin B (10 μg/0.1 mL) following diagnostic vitreous tap 2
• Voriconazole (intravitreal or systemic) is an alternative 2
• Pars plana vitrectomy is sight-saving by removing inflammatory debris 2

For Candida endophthalmitis:

• Fluconazole 800 mg loading dose, then 400-800 mg daily for susceptible isolates 2
• Voriconazole 400 mg IV twice daily for 2 doses, then 300 mg twice daily as alternative 2
• Treatment duration: at least 4-6 weeks 2

Critical Monitoring Requirements During Albendazole Therapy

Albendazole carries significant risks requiring vigilant monitoring 3:

• Monitor blood counts at beginning of each 28-day cycle AND every 2 weeks during therapy 3
• Monitor liver enzymes (transaminases) at beginning of each cycle AND at least every 2 weeks 3
• Discontinue if hepatic enzymes exceed 2x upper limit of normal 3
• Discontinue if clinically significant decreases in blood cell counts occur 3

Fatal outcomes have been reported due to granulocytopenia or pancytopenia with albendazole use 3

Essential Pitfalls to Avoid

• Never start albendazole for neurocysticercosis without ophthalmology screening - retinal cysticercosis can cause devastating inflammatory damage when parasites die 2, 3
• Never treat onchocerciasis without excluding loiasis - can cause severe complications 2
• Never use albendazole in pregnancy - causes embryotoxicity and skeletal malformations 3
• Ensure contraception during albendazole treatment and for 3 days after final dose 3
• Screen for co-infections before prolonged corticosteroid therapy to prevent hyperinfection 1
• For neurocysticercosis patients, always provide concurrent steroids and anticonvulsants to prevent seizures and increased intracranial pressure from inflammatory reactions 3

Geographic and Epidemiologic Considerations

• Toxoplasmosis: Up to 80% seroprevalence in Brazil; more severe genotypes in Central/South America 2
• Onchocerciasis: Near fast-flowing rivers in sub-Saharan Africa, Yemen, and Yanomami areas of Brazil/Venezuela 2
• Malaria retinopathy: Sub-Saharan Africa; retinal ischemia indicates poor prognosis 2
• Lymphatic filariasis: Previously high in equatorial areas, now reduced; endemic in parts of Africa, West Pacific, Caribbean 2