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Corneal Ulcers Versus Infiltrates

Subjective
A 42-year-old daily - wear soft contact lens wearer presented with a history of red right eye for two days. The eye was mildly uncomfortable. After the first day of redness, she discontinued lens wear and, when it appeared no better after the second day, she came to the doctor. She has been wearing soft lenses successfully for eight years and this had never happened before.

Objective

• Visual acuity (VA): 6/6 (20/20) OU
• Eye is injected, mostly in the superior nasal quadrant
• Cornea: clear except for a small, whitish, cloudy lesion near the periphery at the 2 o'clock position (Fig. 1)
• Anterior chamber: deep and clear. The lacrimal lake was clear and devoid of microparticulant debris. Fluorescein instillation revealed a pinpoint epithelial defect over the anterior stromal lesion (Fig. 2)
  
  

  	Fig. 1 This small lesion appearing near the limbus represents an infiltrate secondary to corneal hypoxia from contact lens wear
  	Fig. 2 Epithelial tissue compromise has occurred in this infiltrate resulting in a corneal defect that stains with fluorescein. With an infiltrate, the size of the epithelial defect is usually smaller than the underlying area of stromal infiltration.

Assessment

• Infiltrative keratitis

Plan

• Dexamethasone/tobramycin (Tobradex) ophthalmic suspension q2h. x 2 days, then q.i.d. x 5 days
• In office cyclopentolate hydrochloride (Cyclogyl) 1% 1 gt. OD
• Re-evaluate in 1 to 2 days
• Continue to wear eyeglasses until complete resolution, which was 1 week

Comments: The prime question in this situation is: "Is this an ulcer or an infiltrate?" All findings pointed to an infiltrate. Regarding therapy, a less clinically seasoned or more conservative practitioner may choose to treat with a fluoroquinolone  hourly for a day or two, and then if only minimal improvement at the 1 day or 2nd day follow-up visit (and certainly no worsening since the offending lens is removed), add a steroid, and witness rapid resolution in 2 to 4 days.

It must be remembered that infiltrates are common and ulcers are relatively rare. These ratios vary from practice to practice, depending in large part on the safety and compliance of daily-wear schedules versus extended-wear schedules of contact lens patients. We work diligently to educate our patients about the importance of complying with recommended wearing schedules. Generally speaking, daily, every 2 week, or monthly replacement daily wear schedules are safe, effective, and well accepted by our patients. The newer silicone hydrogels represent a relatively safer approach to extended wearing schedules.

Discussion
Table I shows the differential diagnosis of corneal ulcers versus infiltrates.

Salient Features of Ulcers versus Infiltrates

Corneal Ulcer

• Epidemiology: relatively rare
• Represents active bacterial infection
• Generally causes significant pain
• Tends to be central, rather than peripheral (Staphylococcus exotoxin "peripheral ulcers" are toxic/inflammatory epithelial erosive defects)
• Size of the fluorescein epithelial staining defect closely mirrors the underlying stromal lesion
• Almost invariably a cellular inflammatory response in the anterior chamber
• Pattern of bulbar conjunctival injection is usually generalized, rather than sectorial
• Underlying iris anatomy is commonly obscured
• Treatment is aggressive use of a topical fluoroquinolone, possibly with polysporin ophthalmic ointment at bedtime and daily follow-up until good control is achieved. Therapeutic cycloplegia with 5% homatropine or 0.25% scopolamine is usually wise
  
• Staining, cultures, and sensitivities are mandatory for large, central, vision-threatening ulcers. However, recent articles have shown that for less severe peripheral ulcers, the community standard-of-care is empirical intensive therapy with a fluoroquinolone without culturing.

Medical Therapy

• Theraputic cycloplegia: homatropine 5% or scopolamine 0.25% t.i.d.
• Antibiotic: either levofloxacin 1.5%, moxifloxacin 0.5%, or gatifloxacin 0.3% hourly (while awake) and Polysporin (bacitracin with polymyxin B) ointment at bedtime.
  
• Follow daily
  If the ulcer is in the visual axis, add Pred Forte (prednisolone acetate) q.i.d. once the epithelial defect is nearly closed. This will reduce the potential for scarring. No steroid is needed for lesions outside the visual axis.
  
  We commonly start patients with true infectious keratitis on 100 mg tablets of doxycycline daily for a week or two to reduce the risk of corneal melting. The tetracycline family has excellent activity against collagenase.
  

Corneal Infiltrate

• Epidemiology: relatively common; usually the result of hypoxia
• Represents migration of inflammatory white blood cells from the limbal vasculature and precorneal tear film
• Pain is mild to moderate; rarely marked
• Tends to be peripheral because of the proximity of the cellular inflammatory mechanisms released from the limbal blood vessels
• Size of the fluorescein epithelial staining defect is usually much smaller than the underlying stromal lesion. In any situation where there is stromal inflammation, it is a real challenge for the overlying epithelial cells to remain physiologically intact. This explains why there can be some fluorescein staining in these stromal inflammatory responses
• Secondary anterior chamber reaction is rarely elicited
• Pattern of bulbar conjunctival injection is usually sectored and proximally associated with the infiltrate. Even if there is 360° injection, the vascular injection pattern is skewed toward the sector nearer the infiltrate, particularily if it is peripherally located
• Underlying iris anatomy is generally easily visualized
• Two options for therapeutic approach:
  (1) If diagnosis is clear - antibiotic/steroid combination such as tobramycin with dexamethasone, 1 gt. q.2h. x 2 days, then modify and taper p.r.n.
  (2) If diagnosis is unclear - treat with a fluoroquinolone every 1 to 3 hours and follow up in 24 hours. If it is an ulcer, there may be no or minimal improvement at 24 hours; if the defect is an infiltrate, it will be the same or worse. At day 1 follow-up, the conservative antibiotic therapy can be continued for another day, or, if your diagnostic decision is now an infiltrate, then prescribe a topical steriod such as loteprednol 0.5% (Lotemax) or prednisolone acetate 1% (Pred Forte) along with the antibiotic q.i.d. for four to seven more days.