What is the treatment for myiasis ocular?

Treatment of Ocular Myiasis

The treatment of ocular myiasis requires immediate mechanical removal of all larvae under topical anesthesia, followed by thorough surgical debridement of necrotic tissue, broad-spectrum topical and systemic antibiotics, and tetanus prophylaxis. 1, 2, 3

Immediate Management

Larval Removal

• Mechanical removal of all visible larvae is the cornerstone of treatment and must be performed urgently to prevent rapid tissue destruction and potential intracranial extension 1, 2, 3
• Immobilize larvae with topical 4% lignocaine (lidocaine) before removal to facilitate extraction 4
• Use topical anesthesia for patient comfort during the removal procedure 5, 4
• Remove larvae meticulously from all conjunctival fornices and affected tissues using forceps under slit-lamp or direct visualization 1, 5, 4

Surgical Debridement

• Perform aggressive surgical debridement of all necrotic and infested tissue immediately after larval removal 1, 2, 3
• In cases of extensive orbital involvement with complete tissue destruction, orbital exenteration may be necessary to remove all necrotic tissue and remaining larvae 2, 3
• Reconstruction with pedicled musculocutaneous flaps may be required for large defects following exenteration 3

Antimicrobial Therapy

Topical Treatment

• Apply topical antibiotics (such as tobramycin or fluoroquinolones) to prevent secondary bacterial infection 1, 4
• Consider topical corticosteroids for 2 weeks to reduce inflammation after larval removal in superficial cases 4
• Use cycloplegic agents (cyclopentolate 1%) to reduce pain and prevent synechiae formation 5

Systemic Antibiotics

• Administer broad-spectrum systemic antibiotics immediately to prevent or treat secondary bacterial infection 1, 3
• Continue antibiotic therapy throughout the healing period 3

Tetanus Prophylaxis

• Provide tetanus toxoid therapy as myiasis represents a contaminated wound 3

Imaging and Extent Assessment

• Obtain CT scan to evaluate for orbital and intracranial extension before definitive treatment 1, 3
• MRI may provide additional detail regarding soft tissue involvement and eyeball integrity 3
• Imaging is critical because ophthalmomyiasis progresses rapidly and can lead to life-threatening intracranial extension 1, 2

Wound Management

• Dress wounds regularly following debridement 1
• Allow healing by secondary intention for smaller defects 1
• Monitor closely for recurrence or residual larvae 3

Clinical Pitfalls and Considerations

Risk Factors to Recognize

• Advanced age, debilitation, poor general health, and disorders of consciousness increase susceptibility 2, 3
• Previous ocular trauma or untreated eye injuries are major risk factors 3
• History of eyelid malignancy or previous ocular surgery may predispose to infestation 2

Presentation Patterns

• Ophthalmomyiasis can mimic unilateral conjunctivitis, keratitis, foreign body sensation, or uveitis, making early diagnosis challenging 5, 4
• The disease progresses extremely rapidly and can completely destroy orbital tissues within days, especially in debilitated patients 2
• Larvae may be visible wriggling out of tissues or detected on slit-lamp examination 3, 5

Species Considerations

• Chrysomya bezziana (Old World screwworm) causes particularly aggressive tissue destruction 1, 2
• Oestrus ovis (sheep nasal botfly) is the most common cause and typically causes less severe external ophthalmomyiasis 5, 4

Expected Outcomes

• With prompt mechanical removal and appropriate antibiotic therapy, superficial cases typically show symptom regression within 48 hours 4
• Extensive orbital cases require prolonged follow-up (at least 6 months) to ensure adequate wound healing 3
• Delayed treatment can result in complete eyeball destruction, orbital tissue loss, and potentially fatal intracranial extension 1, 2