What is the diagnosis for a patient presenting with photophobia, hyperemia, ocular pain, and pressure, but no visible corneal abrasion on exam?

Diagnosis: Bacterial Keratitis

The most likely diagnosis is bacterial keratitis, which presents with identical symptoms to corneal abrasion (photophobia, redness, pain, and pressure sensation) but without a visible epithelial defect on examination. 1

Key Diagnostic Features

Bacterial keratitis characteristically presents with:

• Pain, redness, photophobia, and foreign body sensation - the exact symptom constellation mimicking corneal abrasion 1
• Suppurative stromal infiltrates with indistinct edges, typically >1 mm in size 1
• Anterior chamber reaction often present even without visible epithelial defect 1
• White cell infiltration in surrounding stroma with edema 1

Critical Examination Findings to Confirm

On slit-lamp biomicroscopy, specifically look for:

• Stromal infiltrates - the hallmark finding that distinguishes this from simple abrasion 1
• Corneal edema surrounding the infiltrate 1
• Anterior chamber cells and flare indicating intraocular inflammation 1
• Conjunctival injection and chemosis 1
• Epithelial defect may be present or absent 1

Differential Considerations

While bacterial keratitis is most likely, also consider:

Corneal edema from other causes if symptoms include:

• Diurnal variation (worse upon waking, better later in day) 1
• Blurred or variable vision as primary complaint 1
• History of elevated intraocular pressure or recent corticosteroid use 1

Herpes simplex keratitis - typically unilateral presentation 1

Immediate Management Algorithm

1. Perform fluorescein staining under cobalt-blue light to identify any subtle epithelial defects 2, 3

2. Assess for risk factors that increase bacterial keratitis likelihood:

   • Contact lens wear (especially overnight wear) 1
   • Recent ocular trauma 1
   • Previous corneal surgery 1
   • Dry eye or ocular surface disease 1
   • Immunosuppression 1

3. Obtain cultures if indicated - specifically when infiltrate is:

   • Central location 1
   • Large (>2 mm) 1
   • Associated with significant stromal involvement 1
   • Multiple locations on cornea 1

4. Initiate empiric broad-spectrum topical antibiotics immediately - do not delay for culture results in suspected bacterial keratitis 1

5. Add cycloplegic agent when substantial anterior chamber inflammation is present to decrease pain and prevent synechia formation 1

Critical Pitfalls to Avoid

• Never patch an eye with suspected infection or in contact lens wearers - this increases risk of bacterial keratitis progression 1
• Do not assume absence of visible abrasion excludes serious pathology - bacterial keratitis can present without obvious epithelial defect 1
• Avoid topical corticosteroids initially until organism is identified and infection is responding to therapy (wait 24-48 hours minimum) 1
• Be aware of fluoroquinolone resistance in MRSA and Pseudomonas aeruginosa when selecting empiric therapy 1

Follow-Up Requirements

• Re-evaluate within 24 hours for all suspected bacterial keratitis cases 1
• Monitor for progression of infiltrate, worsening anterior chamber reaction, or development of corneal melting 1
• Adjust antibiotic therapy based on clinical response and culture results if obtained 1