SIGNS AND SYMPTOMS
This nodular inflammation of the peri-limbal tissues occurs secondary to an allergic hypersensitivity response of the cornea. The disease is most common (60 percent of cases) in women during their first and second decades who live in crowded or impoverished quarters.
Patients typically present with symptoms of tearing, ocular irritation, mild to severe photophobia and a history of similar episodes. If the underlying cause is Staphylococcal infection, expect to see a rope-like, mucopurulent discharge as well.
There are two distinct types of phlyctenular lesions: corneal and conjunctival. Under the slit lamp a conjunctival (vascularized) phlyctenule appears as a 1 to 3mm hard, triangular, slightly elevated, yellowish-white nodule surrounded by a hyperemic response, in the vicinity of the inferior limbus. These lesions tend to be bilateral.
Corneal phlyctenules produce more severe symptoms. They usually begin adjacent to the limbus as a white mound, with a radial pattern of vascularized conjunctival vessels. The lesion may then migrate toward the center of the cornea, progressing as a gray-white, superficial ulcer surrounded by infiltrate in the areas where the lesion has been.
The exact mechanism or mechanisms that produce phlyctenules is unclear. Histologically, they are composed of lymphocytes, histocytes and plasma cells. Polymorphonuclear leukocytes are found in necrotic lesions. Their formation seems to be the result of a delayed hypersensitivity reaction to tuberculin protein, Staphylococcus aureus, Coccidioides immitis (a soil-based fungus common in the southwestern U.S.), Chlamydia, acne rosacea, some varieties of interstitial parasites and the fungus Candida albicans. Rarely are cases idiopathic. Such a diagnosis could only be made by exclusion.
Ocular management begins with patient education to improve eyelid hygiene. Lid scrubs two to three times per day along with artificial tears and ointments may soothe and reverse mild cases. Moderate to severe cases require topical steroids or steroid-antibiotic combinations. Cycloplegia is only necessary if there is an associated iritis. In most cases, prednisolone acetate (Pred Forte), one drop, Q2H/QID is sufficient, provided there are no corneal contraindications.
If the suspected etiology is Staph. reaction or acne rosacea, prescribe 250mg of oral tetracycline QID or 250mg erythromycin QID PO, along with topical antibiotic ointments such as bacitracin or erythromycin at bedtime. Topical metronidazole (Metrogel) applied to the skin TID is also effective. Because tetracycline can damage and discolor the teeth of children, it is contraindicated in patients under age 10. In these cases, substitute doxycycline 100mg TID or erythromycin 250mg QID PO. Continue treatment for two to four weeks. In suspicious cases, order a chest X-ray and PPD to rule out tuberculosis.
Maintain the treatment as long as signs and symptoms persist, with follow-up visits weekly. Taper steroids once you see improvement but maintain the antibiotic until the steroid therapy is completely finished. Have patients continue the eyelid hygiene indefinitely.
Other potential differential diagnoses include infiltrates secondary to chronic blepharitis, inflamed pingueculum, herpes simplex and infectious or sterile corneal ulcer. The resurgence of tuberculosis infection makes TB testing almost mandatory.