I have a persistent eye infection despite trying two antibiotics, and I've developed a painful black dot on the inside of my eye, what could this be?

Urgent Ophthalmology Referral Required

You need to see an ophthalmologist immediately—this is not a simple infection that can be managed with antibiotics alone. A painful black dot inside the eye that persists despite two courses of antibiotics suggests either a non-bacterial infection (fungal or parasitic), a corneal foreign body, or severe bacterial keratitis that requires specialized evaluation and treatment 1.

Why This Requires Urgent Specialist Care

The Black Dot Is a Critical Warning Sign

• A visible dark lesion with severe pain disproportionate to clinical findings is characteristic of Acanthamoeba keratitis, a parasitic infection that mimics bacterial infection but doesn't respond to standard antibiotics 1
• Acanthamoeba typically presents with severe pain in excess of findings, and can show ring infiltrates or dark lesions 1
• Fungal keratitis can also appear as a dark infiltrate with a dry appearance, feathered edges, or satellite lesions—features that distinguish it from bacterial infection 1

Antibiotic Failure Demands Broader Investigation

• When two antibiotics fail, the differential diagnosis expands beyond bacteria to include fungi, parasites (Acanthamoeba, microsporidia), and even viral causes with secondary infection 1
• Bacterial keratitis from highly virulent organisms can cause rapid tissue destruction within 24 hours, potentially leading to corneal perforation and endophthalmitis (infection inside the eye) 1
• The ophthalmologist needs to perform corneal cultures and specialized staining to identify the actual pathogen 1

What the Ophthalmologist Will Do

Diagnostic Workup

• Corneal scraping and culture to identify the specific organism (bacterial, fungal, or parasitic) 1
• Confocal microscopy may be used to directly visualize Acanthamoeba cysts or fungal elements 1
• Slit-lamp examination to assess depth of corneal involvement and check for complications like anterior chamber inflammation 1

Specialized Treatment Options

• If Acanthamoeba is confirmed, treatment requires specific anti-amoebic agents (not standard antibiotics), and the condition can take months to resolve 1
• Fungal keratitis requires antifungal medications (topical and sometimes systemic), not antibiotics 1
• Severe bacterial keratitis may need fortified antibiotics (higher concentrations than commercially available) that only specialists typically prescribe 1

Potential Serious Complications Without Proper Treatment

• Corneal perforation leading to loss of the eye 1
• Endophthalmitis (infection spreading inside the eye) 1
• Permanent corneal scarring causing vision loss, even if infection is eventually controlled 1
• Need for corneal transplantation if scarring is severe 1

Critical Pitfalls to Avoid

• Do not continue empiric antibiotic treatment without proper diagnosis—this delays appropriate therapy and allows progression of non-bacterial infections 1
• Do not assume this will resolve on its own—untreated keratitis can progress to blindness within days with virulent organisms 1
• Do not use topical corticosteroids without confirming the diagnosis, as steroids can worsen fungal and Acanthamoeba infections catastrophically 1

Immediate Action Required

Seek ophthalmology evaluation within 24 hours (same-day if possible), as this represents a vision-threatening condition that requires specialized diagnostic equipment and treatment not available in primary care 1, 2, 3. If you experience worsening pain, decreased vision, or increased redness, go to an emergency department immediately 4, 3.