Filamentary Keratitis

Filamentary keratitis.

Signs and Symptoms: Patients presenting with filamentary keratitis generally report ocular discomfort ranging from mild foreign-body sensation to severe pain. Variable tearing and photophobia are likewise present. The condition may be unilateral or bilateral, depending upon the underlying etiology.

Signs include ocular hyperemia particularly in the limbal area, and possibly a pseudoptosis. The hallmark finding is the presence of mucus filaments within the preocular tear film adhering to the corneal surface. These filaments are typically tadpole-shaped (the "head" adheres firmly to the corneal epithelium, while the "tail" floats freely within the tear film). Rose bengal or lissamine green dye makes the filaments more readily visible on biomicroscopy. Other findings may include a reduced fluorescein tear break-up time and a punctate epithelial keratopathy.

Many patients with filamentary keratitis have underlying systemic conditions, particularly connective tissue disorders. The condition may be more common in women and the elderly. Patients with immune deficiencies also are at greater risk.

Pathophysiology: Filamentary keratitis most often accompanies keratoconjunctivitis sicca. Mucous filaments form when the normally soluble mucin component of the tear film becomes corrupted, causing it to precipitate out as particles or strands. Loose, compromised epithelial cells bind with these mucin strands, forming long filaments that adhere to damaged sites on the corneal surface. As the lids open and close with each blink, they tug at the loose end of the filaments, stimulating the pain-sensitive corneal nerves.

Other conditions that can induce a filamentary keratitis include superior limbic keratoconjunctivitis (SLK) of Theodore, prolonged patching following cataract or other ocular surgery, epitheliopathy due to aerosol or radiation keratitis, herpetic keratitis (both simplex and zoster), recurrent corneal erosion, neurotrophic keratitis, bullous keratopathy, and systemic disorders, including diabetes and psoriasis.

Management: Treatment for filamentary keratitis involves eliminating the mucus filaments as thoroughly as possible and addressing the underlying cause. In most cases, management begins with physical removal of the filaments at the slit lamp, using a jeweler's forceps under topical anesthesia. Copious lubrication therapy with artificial tears (preferably non-preserved) helps address the ocular discomfort and rejuvenate the precorneal tear film. Punctal occlusion therapy may help in persistent cases of dry eye.

Antibiotics, Steroids and Combination Medications The anterior eye's limited response to a broad variety of insults sometimes makes it difficult to differentiate viral, bacterial or allergic causes. Using combination medicines such as Tobradex (tobramycin and dexamethasone, Alcon) or Maxitrol (neomycin, polymixin B and dexamethasone, Alcon), is often effective because the medications can simultaneously quiet infection and inflammation. Unfortunately, this approach can also produce complications. Inappropriately prescribed topical steriods can cause herpes simplex epithelial infection to accelerate out of control. In patients with microbial keratitis, increased ulceration and even corneal perforation may ensue if the organism is resistant to the antibiotic. Steroids can also impede healing and cause corneal melting. And in cases where only a steroid is needed, the additional antimicrobial agents may actually produce toxicity.

In more severe cases of filamentary keratitis, pharmaceuticals may help to eliminate the filaments and improve patient comfort. N-acetylcysteine (Mucomyst) is a mucolytic agent used primarily as an inhalant for patients with bronchial disease such as emphysema, pneumonia or cystic fibrosis. In its topical form (2-10%), acetylcysteine effectively dissolves corneal filaments. While not commercially available in the United States, you can readily obtain acetylcysteine from a compounding pharmacist.

Manage more severe forms of filamentary keratitis with a high-water (~70%), soft bandage contact lens with prophylactic antibiotic drops bid-tid. Be prepared to manage this condition for prolonged periods. Filamentary keratitis may take weeks or even months to resolve, depending on the etiology and the aggressiveness of therapy. Even after the filaments dissipate, the underlying disease must be controlled or recurrences are likely.

Clinical Pearls:

• Remember that filamentary keratitis is not a disease per se, but rather a sign of a severe ocular surface disorder. Always determine the root cause of this condition before initiating therapy.
• Inform patients that prolonged therapy may be necessary to alleviate this condition, which is often chronic. Antibiotic solutions do not help as a primary therapy for filamentary keratitis, although they may provide prophylaxis on compromised corneas. Topical corticosteroids or NSAIDs may palliate the associated discomfort, depending on the underlying etiology.
• N-acetylcysteine 5% solution is often available from a compounding pharmacy, and is often helpful in managing filamentary keratitis. Advise patients that this solution may smell like rotten eggs, and can also be quite expensive for a relatively small amount. If formulated without preservatives, the patient must discard it after about 30 days.

Other reports in this section

• Terrien's Marginal Degeneration
• Acanthamoeba Keratitis
• Fungal Keratitis
• Filamentary Keratitis
• Bacterial Keratitis
• Understanding Corneal Topography