Thygeson's Superficial Punctate Keratopathy

SIGNS AND SYMPTOMS
The signs and symptoms of Thygeson's superficial punctate keratopathy (SPK) are minimal. Patients usually report only a mild to moderate foreign body sensation, tearing and occasionally photophobia. There is no history of recent ocular inflammation, nor typically any associated systemic illness. Upon gross inspection, the affected eye appears normal, with little or no evidence of eyelid swelling, conjunctival injection or corneal edema.

Biomicroscopy reveals numerous round or stellate areas of coarse, gray, slightly elevated intraepithelial opacities. These lesions resemble subepithelial infiltrates, but are more superficial, duller in color, and less organized. Also, these areas may demonstrate variable central staining with sodium fluorescein, whereas subepithelial infiltrates typically do not stain. Inspection of the anterior chamber shows neither cells nor flare.

Visual acuity may be normal or mildly reduced, depending upon the density and location of the opacities. Because Thygeson's SPK tends to run a chronic, remittent course, the patient may report similar experiences in the past. The clinical presentation, although bilateral in nature, may be asymmetric, or involve only one eye at a time.

PATHOPHYSIOLOGY
The etiology of Thygeson's SPK is unknown. Research indicates, however, that the condition may be caused by a chronic subclinical viral infection affecting the deeper layers of the corneal basal epithelium. The opacities represent corneal mononuclear cell infiltrates consistent with a viral entity. Studies have implicated a varicella virus, possibly herpes zoster, as well as Chlamydia trachomatis in the development of Thygeson's, although these claims are unsubstantiated.

In most cases, Thygeson's SPK presents with insidious onset. With or without treatment, the lesions will eventually resolve; however, the disease often continues to plague these patients for months or even years, with sporadic exacerbations. The trigger mechanism for these flare-ups appears to be idiopathic.

MANAGEMENT
Thygeson's SPK is a self-limiting disorder, but intervention usually speeds the resolution and enhances patient comfort. Manage mild cases by recommending non-preserved artificial tear preparations, every two to three hours while awake, with bland ophthalmic ointment at bedtime.

Treat more severe presentations with topical steroids, such as 0.1% fluorometholone alcohol (FML) or 1% rimexolone (Vexol). In most cases, QID dosing is adequate, but increase dosage in severe cases if necessary. Continue the treatment for one week, and then slowly taper therapy to avoid a rebound inflammation. Follow up weekly during therapy, then every three to 12 months during remission.

CLINICAL PEARLS

Thygeson's SPK is enigmatic; it presents as a corneal inflammation associated with an essentially white and quiet eye in an otherwise healthy patient. Other conditions that present with corneal infiltrates usually induce at least a related conjunctivitis-the most common of these is epidemic keratoconjunctivitis. Other entities in the differential include: bacterial keratoconjunctivitis, chlamydial keratoconjunctivitis, toxic keratoconjunctivitis, exposure keratopathy and dry eye syndrome.

Because of the chronic, remittent course of this disease, patients often present with their diagnosis "in hand." Patients who are not already aware should be educated about the recurrent nature of Thygeson's SPK, and the need for continued follow-up.