What are the symptoms and treatment options for parasitic eye infections?

Symptoms and Treatment of Parasitic Eye Infections

Parasitic eye infections present with pain, photophobia, decreased vision, and ocular inflammation, with specific symptoms varying by parasite type—toxoplasmosis causes retinochoroiditis, Acanthamoeba causes severe painful keratitis, and ocular toxocariasis presents with visual changes and retinal granulomas. 1

Common Symptoms Across Parasitic Eye Infections

General Presentation

• Pain and photophobia are hallmark symptoms of most parasitic keratitis and intraocular infections 1
• Decreased or blurred vision occurs as the primary complaint in parasitic retinal infections 2, 3
• Ocular inflammation manifests as conjunctival injection, anterior chamber reaction, or vitritis depending on the location of infection 1, 4

Specific Parasitic Presentations

Toxoplasmosis (Most Common Parasitic Eye Infection)

• Causes retinochoroiditis with characteristic retinal lesions 1
• Patients report blurred vision as the main complaint 2
• Can present with recurrent necrotizing retinitis near old scars, requiring long-term monitoring 1
• The Central and South American genotype causes more severe inflammatory response 1

Acanthamoeba Keratitis

• Presents with severe, excruciating pain disproportionate to clinical findings 5
• Associated with contact lens wear in most cases, though non-contact lens wearers are increasingly affected 1, 5
• Can cause corneal ulceration, loss of visual acuity, and potentially blindness or enucleation if untreated 5
• Confocal microscopy is particularly useful for identifying this organism 1

Ocular Toxocariasis

• Presents with visual changes, retinal granuloma, or uveitis 6, 7
• Typically a monocular disease of young children 3
• Eosinophilia is less common in isolated ocular disease compared to systemic toxocariasis 6, 7
• May cause epiretinal membrane formation, traction retinal detachment, and combined traction-rhegmatogenous detachment 3

Onchocerciasis (River Blindness)

• Causes keratitis, uveitis, and choroidoretinitis leading to eventual blindness 1
• Travelers typically present with mild to intense pruritus and limb swelling rather than full-blown ocular disease 1
• Requires urgent ophthalmology assessment before treatment 1

Malaria Retinopathy

• Pathogenesis involves vessel occlusion and ischemia similar to cerebral malaria 1
• Retinal ischemia in severe malaria indicates poor prognosis 4
• No specific treatment exists for malaria retinopathy itself 1

Treatment Approaches

Toxoplasmosis Treatment

• Requires combination drug therapy to eliminate the parasite and control inflammation 2
• Multiple drug combinations are used, though specific regimens vary 2
• Untreated cases can lead to vision loss 2

Ocular Toxocariasis Treatment

• Albendazole 400 mg twice daily for 2 weeks combined with corticosteroids is the recommended treatment 6
• Joint management with an ophthalmologist is essential 6
• Corticosteroid therapy controls the inflammatory response 6
• For significant vitreous involvement, intravitreal injections may be considered 6
• Vitrectomy should be considered in cases with significant vitreous opacity 6

Acanthamoeba Keratitis Treatment

• Requires emergency ophthalmologic intervention with topical antifungal therapy 1
• Systemic antifungal therapy with amphotericin B, voriconazole, or itraconazole is recommended 1
• Treatment is challenging due to the highly resistant cyst stage of Acanthamoeba 5
• Misdiagnosis or late diagnosis leads to severe outcomes 5

Onchocerciasis Treatment

• Exclude loiasis prior to treatment and seek expert advice in co-infection 1
• 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
• Repeat ivermectin every 3-6 months until asymptomatic, then annually if necessary 1

General Principles for Parasitic Endophthalmitis

• Intravitreal amphotericin B (10 mg dose) plus pars plana vitrectomy may be sight-saving 1
• Voriconazole administered intravitreally or systemically is an alternative regimen 1
• Systemic amphotericin B and itraconazole penetration into vitreous and aqueous humor is often inadequate 1

Critical Diagnostic Considerations

When to Suspect Parasitic Infection

• Travel history to tropical and subtropical regions is essential 1
• Contact lens wear raises suspicion for Acanthamoeba 1, 5
• Consumption of undercooked meat or shellfish suggests toxoplasmosis 1
• Contact with contaminated soil or infected puppies indicates possible toxocariasis 7, 3

Diagnostic Pitfalls

• Medication toxicity can mimic worsening infection, causing persistent inflammation or corneal melting 1
• Confocal microscopy is particularly helpful for identifying Acanthamoeba and other parasites 1
• Reculture may be necessary if there is lack of favorable clinical response, with discontinuation of antibiotics for 12-24 hours prior to increase yield 1
• Vitreous or aqueous humor culture is required for definitive diagnosis of endophthalmitis 1

Geographic Risk Factors

• Toxoplasmosis prevalence reaches 80% in Brazil with more virulent genotypes in Central and South America 1
• Malaria retinopathy occurs particularly in Sub-Saharan Africa 1
• Onchocerciasis is found near fast-flowing rivers in Africa south of the Sahara, Yemen, and parts of South America 1

Prevention Strategies

• Effective chemoprophylaxis is available for malaria, including hydroxychloroquine (though retinopathy risk exists with long-term use) 1
• Insect repellent, minimizing skin exposure, and avoiding forested and still water environments reduce malaria and onchocerciasis risk 1
• Proper contact lens hygiene reduces Acanthamoeba keratitis risk 1, 5
• Washing fruits and vegetables thoroughly and avoiding contaminated soil prevents toxocariasis 7