Marginal Infiltrative Keratitis
BY WILLIAM L. MILLER, OD, PHD, FAAO
As a follow up to my August Column "Managing Blepharitis," I will discuss an often encountered sequelae to severe blepharitis: marginal infiltrative keratitis (MIK). Commonly due to a hypersensitivity reaction to the Staphylococcal species, it often does not represent a frank infection by this species. The two most frequently isolated causative agents are Staphylococcal epidermidis and aureus. The body's response to the immune challenge leads to an infiltration of polymorphonuclear leukocytes into the limbal region.
Your patient may present with irritation, itching, photophobia, redness, grittiness, or foreign body sensation — none of which are specific for MIK. Because the bacteria tend to populate the lid and lash margin, patients will likely have a moderate-to-severe and often long-standing blepharitis with intermittent episodes of symptomatic flare ups. Hyperemia will be present over the entire conjunctival surface.
In episodic and severe cases, marginal areas of infiltrates will develop with a lucid interval between the infiltrates and limbal region. Solitary or multiple infiltrates may present and often form on areas of the cornea that are directly opposed to the lid margin from 4 o'clock to 8 o'clock or from 10 o'clock to 2 o'clock. The infiltrates can be chalky and densely populated with resultant scarring possible. Superficial punctate staining may overlie the infiltrate, and a corneal ulcer may result depending on the severity of the inflammation. Such corneal ulcerations may present a diagnostic challenge because they often mimic infectious keratitis. In frequent attacks, the peripheral cornea can also exhibit vascularization with simultaneous scarring and fibrosis.
Patients who develop MIK often will not seek care and will suffer through what they believe is just a "red eye," as the MIK will disappear after a few weeks even without treatment. However, the lasting effects of scarring and vessel growth will remain.
Even though MIK can be self-limiting, treatment options allow for quicker resolution and improvement in the patient's quality of life. Cultures are usually not warranted unless, as in the case of infectious keratitis, the condition does not improve with therapeutic interventions.
Start by treating the blepharitis. The eyelid and corneal treatments are aimed at decreasing the inflammation and protecting the surface from infection. When the cornea is intact or has minor punctate staining, your primary goal is to decrease inflammation caused by the Staph. hypersensitivity reaction through judicious use of corticosteroids; the specific steroid will depend on the severity of the MIK. Most cases resolve quickly with the use of steroids and synchronous treatment of the blepharitis. If there is a delay in resolution, carefully revisit your differential diagnoses.
I prefer to treat the blepharitis with conservative medical therapy and add to this a topical steroid, either Pred Forte (Allergan) or Lotemax (Bausch & Lomb), q.i.d. for five days or until the condition has resolved. For cases with more severe punctate fluorescein staining, use Tobradex (Alcon) or Zylet (Bausch & Lomb) every two-to-four hours for the first day or two and then decrease to q.i.d. until day 5 or when resolved. This treatment plan can continue beyond five days for cases in which the drop is also being used to control the blepharitis. Treatment duration will then depend on the resolution of both conditions.
Schedule a follow up for 24-to-48 hours after the initiation of therapy to monitor therapeutic progress. Follow the usual caveats to topical steroid use including cessation of therapy if the condition worsens and monitoring intraocular pressure as well as strict patient education regarding the timeline for use. CLS
Dr. Miller is an associate professor and chair of the Clinical Sciences Department at the University of Houston College of Optometry. He is a member of the American Optometric Association and serves on its Journal Review Board. You can reach him at firstname.lastname@example.org.