Article Date: 1/1/2012

Part 1: Corneal Breach
contact lens complications

Part 1: Corneal Breach

The risk factors, symptoms, signs and treatment of infectious keratitis

Susan Kovacich, O.D., F.A.A.O.
Bloomington, Ind.

While contact lens wear is a benefit to millions of patients worldwide, we know that complications with wear can and do occur. After all, the biocompatible material rides on the thin tear film, placing it in close proximity to the cornea and conjunctiva. Given this inherent risk, it's essential we're aware of these complications so we can educate patients on how to prevent them, and we can diagnose and effectively treat these complications, should they develop.

Here, in part one of this three-part series on contact lens complications, I discuss infectious keratitis.

Organism invasion

Infectious keratitis occurs when contact lens wear has compromised the eye's natural defense mechanisms, enabling extraneous organisms, which can be bacterial (most commonly), fungal or protozoan,

to invade the cornea. Specifically, infectious organisms can bind to and colonize on the contact lens surface, and contact lens wear can irritate the cornea or disrupt the tear film, enabling a breach of the corneal epithelium. This invasion can result in corneal scarring, loss of best-corrected vision and even loss of the eye itself.

The good news: Infectious keratitis is relatively rare. Studies have suggested that the rate of MK for all wear schedules in hydrogel lenses is 4.1/10,000 annually, while the rate in silicone hydrogel (SiHy) lenses is 11.9/10,000.1

Risk factors

In developed countries, such as the United States, contact lens wear is the most common risk factor for the development of infectious keratitis, and it is more common in soft contact lenses compared with GP lenses. A possible reason for this is that GP lenses allow better tear exchange with blinking than soft contact lenses, enabling microbes to be flushed out from underneath the lens.2 Extended and continuous lens wear, which reduce tear exchange even more, is the biggest risk factor in the development of infectious keratitis, with an increase to 20.9/10,000 contact lens wearers annually (a five-fold increase) in hydrogel lenses.3 The rate of infectious keratitis in 30-day continuous wear SiHy lenses is similar at 18/10,000.4

Other risk factors for infectious keratitis: Young age (18 to 22 years-old), male gender, smoking, swimming while wearing contact lenses and the presence of lid disease — specifically posterior blepharitis. Young male patients may have a tendency toward risky behaviors for infectious keratitis, such as non-compliance with contact lens wearing time, replacement and care, which predisposes them to all three types of infectious keratitis, but specifically bacterial (often referred to as microbial keratitis or MK) in developed countries.5 All varieties of infectious keratitis are associated with poor contact lens disinfection. Acanthomoebic keratitis is associated with water. Activities, such as swimming in lakes, using a hot tub and showering while wearing contact lenses are risk factors for the development of this condition.

Because the aforementioned characteristics place patients at risk for infectious keratitis, be sure to ask the patient who presents with infectious keratitis symptoms (described below) about his contact lens wear and care regimen and the outlined risky behaviors during the patient history portion of the exam. Doing so will help you determine what type of infectious keratitis with which you may be dealing.

Symptoms

Because the cornea is highly innervated with pain receptors, the patient who has infectious keratitis usually presents sans contact lens in the affected eye and a tremendous amount of eye pain. This pain usually has begun in often a day or less. Specifically, the patient complains of a dull ache that radiates from behind the affected eye. I've found that patients who have infectious keratitis will often report their level of pain in the nine-to-10 range when asked: “On a scale of one to ten, with ten being the worst, what is the amount of pain that you are feeling?”

Other symptoms of infectious keratitis: photophobia, mucous discharge, ocular redness and a decrease in vision. With regard to the photophobia, some infectious keratitis patients may arrive at your practice wearing sunglasses or covering the affected eye to protect it from the light.

Because the severe pain and photophobia make these patients difficult to examine, you may have to instill a drop of topical anesthetic to do so. Any instillation of drops should occur after obtaining the patient's visual acuities, if possible. (This is important for legal reasons — see below.). Sometimes, patients are in so much pain, that they cannot open their eyes or look toward the acuity chart.

Signs

Patients who have MK usually present with significant upper lid swelling (“lid reaction”) in the affected eye. The conjunctival injection tends to be 360° or circumferential. The corneal epithelium is disrupted over a white blood cell infiltration. The focal infiltrate tends to be white with mucous formation, surrounding corneal edema and located toward the visual axis (away from the periphery) (See Image 1, below). The infiltrative lesion (ulcer) tends to be irregular in shape, large (2+ mm) and is deep into the corneal stroma, excavating past Bruch's membrane — a hallmark of MK. This results in corneal thinning. Upon fluorescein staining, you'll notice the pattern closely matches the size of the ulcer. You'll note white blood cells in the anterior chamber, and in severe cases the white blood cells will settle out in the anterior chamber, resulting in a hypopyon.

Image 1: MK infiltrates tend to be white with mucous formation, surrounding corneal edema and located toward the visual axis.

Meanwhile, the appearance of the corneal infiltrate in fungal keratitis may be pigmented or colored — often having a grayish coloration — and can have feathery borders with multiple smaller lesions, or “satellite lesions,” surrounding the primary infiltrate.A classic sign of the protozoan infection Acanthamoeba keratitis is radial perineuritis.

Image 2: Note how this fungal keratitis infiltrate is gray with feathery borders.

Image 3: Acanthamoebic keratitis has the classic sign of radial perineuritis.

These signs and symptoms are in contrast to a contact lens peripheral ulcer (CLPU), which is a small focal infiltrate (1mm to 2mm) and tends to be very round and close to the periphery of the cornea. It is much more superficial than MK infiltrates. If any anterior chamber reaction is present, it tends to be mild. Also, any discharge will be watery or serous.

To document the improvement or worsening of the particular infectious keratitis with which you are dealing, keep a thorough record that includes the size, location and depth of the lesion along with the amount of white blood cells found in the anterior chamber.

Treatment

Because infectious keratitis can result in corneal scarring, loss of best-corrected vision and loss of the eye itself, it requires aggressive treatment. To start, inform the patient to cease contact lens wear for the duration of the condition. (Keep in mind that these patients may not have an up-to-date spectacle prescription. As a result, visual acuity should be recorded and pinhole acuity should be taken if the vision — corrected or uncorrected — is 20/30 or poorer, for legal reasons.)

Most infectious keratitis associated with contact lens wear is bacterial. Therefore, with the advent of effective topical antibiotics, eyecare practitioners often treat less severe corneal ulcers empirically as bacterial without culturing the infiltrate, which is somewhat controversial (see culturing guidelines below). This treatment is recommended by Melton and Thomas6: a loading dose of a topical fourth-generation fluoroquinolone to be used every 15 minutes for the first three-to-six hours, then hourly until bedtime, and prior to bedtime a broad-spectrum antibiotic ointment instilled in the lower cul de sac. A cyloplegic agent is prescribed b.i.d. to t.i.d. for the management of photophobia and anterior chamber inflammation and to prevent synechia.

Treatments to suppress corneal inflammation and scarring include oral doxycycline and topical corticosteroids. Topical corticosteroids should not be used in the first 48 hours, or until antimicrobial treatment has sterilized the ulcer, and should only be used when the clinical picture of a microbial keratitis is improving. Note that topical corticosteroids are only indicated with microbial keratitis: They are contraindicated in other causes of infectious keratitis. Fungal keratitis, in particular, can become exacerbated with corticosteroid treatment.

Due to the serious consequences of keratitis, it's essential you follow the patient every 24 hours until you note improvement of the clinical picture and an improvement in pain. Both should occur within the first 24-to-48 hours post-treatment. Once you see improvement and the patient reports less pain, slowly taper the fourth-generation fluoroquinolone drop to q.i.d., while following the patient every few days. Instruct the patient to return as soon as possible if the pain increases or his vision worsens.

If the condition does not respond to the bacterial treatment regimen within 24-to-48 hours, refer the patient to a corneal specialist for lesion culturing to identify the offending pathogen, and prescribe the appropriate treatment regimen, which may include fortified antibiotics. The contact lens and contact lens case should also be cultured if possible, since corneal yield can be low and the lens/case can harbor infectious organisms.

Fungal infectious keratitis is usually treated for four-to-six weeks with antifungal drugs, such as natamycin and amphotericin B. Meanwhile, Acanthomoeba keratitis is often managed for several months — it is not uncommon for difficult cases to be managed medically for up to six months — with various topical agents, such as polyhexamethylene biguanide (PHMB) and propamidine isethionate (Brolene, Sanofi-Aventis).

If during the initial exam, the cornea is significantly thin, the lesion is on or near the visual axis (within 1mm) with two or more infiltrates (indicating a fungal or atypical lesion); very large (3mm or larger) (“the 1,2,3 Rule”); or if it is more than 2mm away from the limbus, deep (more than 20% to 25% of the cornea), or grade 2 white blood cells are present in the anterior chamber (“the Rule of 2's”), you should refer the patient to a corneal specialist for lesion culturing that day to determine whether the condition is microbial, fungal or protozoan (Acanthamoeba). Culturing can take several days to more than a week, complicating the treatment process. If the corneal ulcer does not respond to standard antimicrobial therapy, the treatment will have to be modified and is often tailored to the clinical picture and history while waiting for the results of the culture.

Prevention

Even with appropriate treatment, the infectious keratitis patient may be left with corneal scarring or an irregular cornea and a permanent reduction in best-corrected visual acuity. Therefore, we must do our best to prevent the condition's onset in the first place. To accomplish this, advise lens wearers on the correct wear and care of their lenses at the initial appointment and every subsequent appointment. (Studies have shown that compliance to the prescribed wear-and-care regimen decreases with time.7) The Association of Optometric Contact Lens Educators (AOCLE) has a printable handout on Healthy Soft Contact Lens Habits that you can give to patients to remind them of the proper handling of their lenses (http://aocle.org/healthyHabits.html). In addition, instruct these patients to return to your practice as soon as possible, should their vision decrease and/or their eye become red and painful. Our staff makes a point of telling our contact lens wearers: “If the eye doesn't look good, feel good, or see good, we need to see you right away.” OM

In Part Two of this three-part series, I'll discuss inflammatory keratitis.

1. Stapleton F, Keay L, Jalbert I, Cole N. The epidemiology of contact lens related infiltrates. Optom Vis Sci. 2007 Apr; 84(4):257-72.
2. Fleiszig S, Evans D. Pathogenesis of contact lens-associated microbial keratitis. Optom Vis. Sci. 2010 Apr; 87 (4):226-32
3. Poggio EC, Gylnn RJ, Schein OD, et al. The incidence of ulcerative keratitis among users of daily-wear and -extended wear soft contact lenses. N Engl J Med. 1989 Sep 21; 321(12):779-83.
4. Schein OD, McNally JJ, Katz J, et al. The incidence of microbial keratitis among wearers of a 30-day silicone hydrogel. Ophthalmology. 2005 Dec; 112(12):2172-9.
5. Keay L, Stapleton F, Schein O. Epidemiology of contact lens-related inflammation and microbial keratitis: a 20-year perspective. Eye Contact Lens. 2007 Nov; 33(6 Pt 2):346-53, discussion 362-3.
6. Review of Optometry. 2010 Clinical Guide to Ophthalmic Drugs. Randall K. Thomas O.D. and Ron Melton, O.D. www.revoptom.com/supplement_toc/s/129/ (Accessed 12/20/11')
7. Collins MJ, Carney LG. Compliance with care and maintenance procedures amongst contact lens wearers. Clin Exp Optom 1986;9:174-77

Dr. Kovacich is the chief of the Cornea and Contact Lens Service at Indiana University School of Optometry, where she is an associate clinical professor and is a consultant for Alcon and Allergan. E-mail her at skovach@indiana.edu, or send comments to optometricmanagement@gmail.com.


Optometric Management, Volume: 47 , Issue: January 2012, page(s): 48 - 51