Bacterial Keratitis Treatment & Management

If no organisms are identified on the slide smear, initiate broad-spectrum antibiotics with the following: tobramycin (14 mg/mL) 1 drop every hour alternating with fortified cefazolin (50 mg/mL) 1 drop every hour.

If the corneal ulcer is small, peripheral and no impending perforation is present, intensive monotherapy with fluoroquinolones is an alternative treatment. Other antimicrobials can be used, depending on the clinical progress and laboratory findings.

The fourth-generation ophthalmic fluoroquinolones include moxifloxacin (VIGAMOX, Alcon Laboratories, Inc, Fort Worth, TX) and gatifloxacin (Zymar, Allergan, Irvine, CA), and they are now being used for the treatment of bacterial conjunctivitis. Both antibiotics have better in vitro activity against gram-positive bacteria than ciprofloxacin or ofloxacin. Moxifloxacin penetrates better into ocular tissues than gatifloxacin and older fluoroquinolones; in vitro activity of moxifloxacin and gatifloxacin against gram-negative bacteria is similar to that of older fluoroquinolones. Moxifloxacin also has better mutant prevention characteristics than other fluoroquinolones. These findings support the use of the newer fluoroquinolones for the prevention and treatment of serious ophthalmic infections (eg, keratitis, endophthalmitis) caused by susceptible bacteria.

In view of these findings, moxifloxacin or gatifloxacin may be a preferred alternative to ciprofloxacin as the first-line monotherapy in bacterial keratitis.

Additionally, 0.5% moxifloxacin and, to a lesser extent, levofloxacin and ciprofloxacin have demonstrated significant effectiveness for reducing the number of Mycobacterium abscessus in vivo, suggesting the potential use of these agents in prevention of M abscessus keratitis.

Three patients with Acanthamoeba keratitis were successfully treated with a topical application of 0.1% riboflavin solution and 30 minutes of UV irradiation focused on the corneal ulcer.^[2]

The frequency of antibiotic administration should be tapered off according to the clinical course using some of the following parameters:

• Blunting of the perimeter of the stromal infiltrate
• Decreased density of the stromal infiltrate
• Decreased stromal edema and endothelial inflammatory plaque
• Decreased anterior chamber inflammation
• Reepithelialization of the corneal epithelial defect
• Improvement in painful symptoms

The most common cause of corneal perforation is infection by bacteria, virus, or fungus, accounting for 24-55% of all perforations, with bacterial infections being the most common. PK, sclerocorneal patch, or application of cyanoacrylate tissue adhesive may be necessary in cases of corneal perforation or imminent perforation, following the guidelines provided below.

• Systemic intravenous antibiotics (alternatively ciprofloxacin 500 mg PO bid) should be started once an infected corneal ulcer has perforated and for 3 days following the PK.
• A clear plastic shield should be placed over the eye.
• The use of general anesthesia usually is preferred for keratoplasty surgery. Topical anesthesia can be used for application of tissue adhesive.
• The size of the transplant should be the smallest trephine capable of incorporating the perforation site and any infected or ulcerated border. Donor generally is oversized by 0.5 mm.
• Cataract removal is left for a subsequent procedure because of the risk of expulsive hemorrhage and endophthalmitis.
• Posterior and anterior synechiae should be lysed gently.
• The anterior chamber should be irrigated to remove any necrotic or inflammatory debris.
• The donor cornea should be secured with 16 interrupted 10-0 nylon sutures.
• Subconjunctival injections of antibiotics can be given without depot steroid injection.
• Postoperative use of frequent topical fortified antibiotics. Corticosteroids 4 times a day can be used immediately after surgery if it is believed that the infection was excised completely. Alternatively, steroids can be withheld for several days to monitor for infection. Once the acute postoperative period is over, long-term care is similar as that for uncomplicated PK.

Consultation with vitreoretinal colleagues may be helpful if the diagnosis of endophthalmitis is considered.