What is the treatment for eye pain caused by parasites?

Treatment of Eye Pain Caused by Parasites

For parasitic eye infections causing pain, treatment depends on the specific parasite identified, with Acanthamoeba keratitis requiring emergency topical and systemic antifungal therapy, ocular toxocariasis requiring albendazole 400 mg twice daily for 2 weeks plus corticosteroids, and neurocysticercosis requiring specialist consultation with consideration of albendazole plus corticosteroids after excluding retinal involvement. 1

Immediate Diagnostic Priorities

Before initiating treatment, specific diagnostic steps are critical:

• Obtain travel history to tropical and subtropical regions, as this raises suspicion for specific parasites 1
• Assess contact lens use, which strongly suggests Acanthamoeba keratitis 1, 2
• Perform confocal microscopy when available, as this is particularly useful for identifying Acanthamoeba and other parasites in corneal tissue 3, 1
• Conduct dilated fundoscopic examination to identify retinal lesions, particularly before treating neurocysticercosis, as retinal involvement contraindicates antiparasitic therapy due to risk of inflammatory damage 3, 4
• Screen for ocular cysticercosis using indirect funduscopy or ocular ultrasound before initiating treatment for neurocysticercosis 3

Treatment by Specific Parasite

Acanthamoeba Keratitis

This is an ophthalmologic emergency requiring immediate specialist intervention:

• Emergency ophthalmologic consultation with topical antifungal therapy is mandatory 1, 5
• Systemic antifungal therapy with amphotericin B, voriconazole, or itraconazole is recommended 1, 5
• Discontinue contact lens use immediately in all cases 5
• This infection is severe, painful, and can lead to corneal ulceration and blindness if not treated promptly 2

Ocular Toxocariasis

Joint management with ophthalmology is essential:

• Albendazole 400 mg twice daily for 2 weeks combined with corticosteroids 3, 1
• Corticosteroid therapy (topical or systemic) controls the inflammatory response that causes vision loss 1
• Intravitreal injections may be considered for significant vitreous involvement 1
• Vitrectomy should be considered in cases with significant vitreous opacity 1
• Note that eosinophilia is less common in isolated ocular toxocariasis compared to systemic disease 3, 1

Neurocysticercosis with Ocular Symptoms

Critical warning: Exclude retinal involvement before treatment:

• Perform fundoscopic examination before initiating antiparasitic therapy, as retinal cysticercosis is a contraindication to albendazole due to risk of inflammatory retinal damage 3, 4
• Discuss with specialist parasitology center before initiating treatment 3
• Corticosteroids must be started one day before praziquantel to prevent inflammatory complications 3
• Dexamethasone 6-8 mg/day for 10-28 days has been used, with higher doses associated with fewer seizures 3
• Praziquantel plus albendazole is superior to albendazole alone in patients with >2 cysts 3
• Monitor for hepatotoxicity with liver enzymes before each cycle and every 2 weeks during treatment with albendazole 4
• Monitor blood counts at the beginning of each 28-day cycle and every 2 weeks, as albendazole can cause bone marrow suppression 4

Onchocerciasis

For travelers with ocular onchocerciasis:

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

Parasitic Endophthalmitis

This is a sight-threatening emergency:

• Intravitreal amphotericin B (5-10 μg/0.1 mL sterile water) plus pars plana vitrectomy may be sight-saving 3, 6, 1
• Voriconazole (100 μg/0.1 mL) administered intravitreally is an alternative 3, 6
• Systemic antifungal therapy with liposomal amphotericin B 3-5 mg/kg IV daily with or without oral flucytosine 25 mg/kg four times daily 3, 6
• Treatment duration should be at least 4-6 weeks, with final duration depending on resolution of lesions 3, 6
• Vitrectomy decreases organism burden and removes fungal abscesses inaccessible to systemic agents 3, 6

Critical Pitfalls to Avoid

• Never initiate antiparasitic therapy for neurocysticercosis without first excluding retinal involvement, as inflammatory death of retinal parasites can cause permanent vision loss 3, 4
• Never use antiparasitic agents in patients with increased intracranial pressure from diffuse cerebral edema or untreated hydrocephalus, as they can worsen cerebral edema 3
• Always start corticosteroids before antiparasitic therapy in neurocysticercosis to prevent inflammatory complications including seizures 3, 4
• Do not use subconjunctival antibiotic injections alone for endophthalmitis, as they are ineffective without intravitreal administration 6
• Exclude strongyloidiasis before initiating prolonged corticosteroid therapy, as steroids can cause fatal hyperinfection syndrome 3
• Monitor for rebound perilesional edema when tapering corticosteroids in patients with calcified lesions 3

Special Monitoring Requirements

• Hepatic enzymes should be monitored before each treatment cycle and every 2 weeks during albendazole therapy; discontinue if levels exceed twice the upper limit of normal 4
• Blood counts require monitoring at the beginning of each 28-day cycle and every 2 weeks, with more frequent monitoring in patients with liver disease 4
• Pregnancy testing is recommended for females of reproductive potential before initiating albendazole, and effective contraception should continue during treatment and for 3 days after the final dose 4
• Ophthalmologic follow-up is essential to monitor response to treatment and assess for complications 6, 1