Thursday, December 23, 2010

Superior Limbic Keratoconjunctivitis (SLK of Theodore)

Signs and Symptoms
Individuals presenting with SLK typically report symptoms of ocular discomfort, including burning, foreign-body sensation, or non-descript pain. Additionally, patients may complain of photophobia and excessive tearing. Gross clinical signs often include mild lid swelling and pseudoptosis as well as blepharospasm. Visual acuity is usually not affected.

Inspection of the ocular surface in SLK reveals a sectoral inflammation and injection of the superior bulbar conjunctiva. The limbal margin of the cornea may be inflamed as well. Eversion of the upper lid reveals a uniform papillary hypertrophy along the tarsus, which may be mild to marked. Vital dye staining is standard in SLK, with patients displaying punctate epithelial disruption of the affected region; this is evident with both sodium fluorescein dye as well as rose bengal or lissamine green solutions. Filaments are encountered within the precorneal tear film in roughly half of all patients with SLK. The condition is typically bilateral but often asymmetric. In most instances, the diagnosis of SLK is based solely upon the characteristic presentation. The only known laboratory confirmation is the presence of keratinized epithelial cells from scrapings of the affected superior bulbar conjunctivae.

The exact etiology and pathogenesis of SLK remains unclear. Infectious agents such as bacteria, viruses, fungi, and other intracellular parasites appear to be unrelated to this condition. An autoimmune etiology has been considered, based upon the pattern of the disorder (i.e., exacerbations and remissions), the female predominance, and an association with thyroid disease and other autoimmune diseases.

The most widely accepted theory regarding the pathogenesis of SLK is that it results from mechanical irritation of the superior limbal region, as loose conjunctival tissue rubs against the limbus during blinking. Factors such as tight lids, prominent globes, and thyroid disease have been offered as potential instigators of this reaction.

A newer theory regarding the etiology of SLK implicates a local tear deficiency to the superior keratoconjunctiva. Researchers have proposed that this deficiency results in significantly reduced levels of vital tear-based nutrients to the affected region, as well as increased mechanical friction from the superior lid.

SLK is a chronic, recurrent and sometimes recalcitrant disorder. While no treatment has yet been shown to be 100 percent effective, many modalities have been employed successfully. The treatment of choice for most practitioners has been 0.5 to 1.0% silver nitrate solution, applied topically to the superior bulbar and tarsal conjunctivae. This treatment chemically cauterizes the irregular tissue, promoting regrowth of new, healthy epithelium. Unfortunately, recurrences have been known to occur after using silver nitrate, and retreatments are common.

Pressure patching has been employed for severely symptomatic cases of SLK, as well as the use of subsequent bandage hydrogel lenses to alleviate the mechanical irritation. Thermal cauterization as well as surgical recession or resection of the superior bulbar conjunctiva has also been employed as treatment modalities for SLK. The use of topical preparations, including vitamin A eyedrops, 4% cromolyn sodium solution, and Alomide (0.1% lodoxamide tromethamine solution, Alcon) have also been somewhat effective in managing SLK. Most recently, lacrimal punctal occlusion therapy has been advocated for this disorder.

Clinical Pearls

In managing this disorder, topical agents should be employed in the early stages of all mild and moderate presentations; thermocautery, chemocautery, and surgical resection should be employed only when less invasive means have failed.
Lacrimal occlusion therapy may prove to be a viable option for SLK; while additional research is needed in this area, recent studies have shown great potential.
SLK of Theodore should not be confused with contact lens-induced SLK (CL-SLK), a condition that is occasionally observed in young, otherwise healthy hydrogel lens wearers. An association with thimerosal-preserved solutions has been seen in some of these patients. The typical presentation of CL-SLK consists of increasing contact lens intolerance, superior tarsal and bulbar injection, and significant superior corneal staining with stromal hazing. Corneal involvement may be noted as far inferiorly as the superior pupillary margin. Treatment for CL-SLK consists of temporarily discontinuing contact lens wear, along with the liberal use of preservative-free ocular lubricants. Upon resolution, contact lens wear may be resumed with a fresh pair of lenses, however all thimerosal-preserved solutions should be terminated. In more severe or recurrent cases, patients may need to be refit with RGP materials.
Refer all patients presenting with SLK for a systemic workup, including a serologic thyroid panel. A 1995 study demonstrated a 65 percent correlation between SLK and systemic thyroid disease. Other disorders such as rheumatoid arthritis and Sj√∂gren’s syndrome may also have similar associations.

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