Diffuse lamellar Keratitis
Diffuse lamellar keratitis (DLK) describes a rare, noninfectious complication of refractive surgery that is characterized by inflammatory infiltrates beneath the corneal flap interface. The characteristic accumulation of fine white infiltrates manifests clinically as a grainy corneal opacification that has led some to describe the condition as “sands of Sahara syndrome”.
The characteristic clinical presentation in DLK develops 1 to 2 days following refractive surgery and typically resolves 5-8 days after the initiation of appropriate therapy . The post-surgical corneal opacification that accompanies DLK is typically nonlocalized and subepithelial.
DLK is divided into four stages according to the extent of corneal involvement.
Stage 1 typically arises 1-2 days after refractive surgery. It is characterized by peripheral inflammatory infiltrates without central corneal involvement.
Stage 2 typically arises on postoperative days 3-4 when inflammatory cells begin migrating from the periphery into the central cornea often comprising visual acuity.
Stage 3 is characterized by further centripetal migration of inflammatory cells and the development of permanent corneal scarring. Stage 3 is often referred to as the “threshold” DLK subtype because of the likelihood that eyes in this stage of DLK will develop permanent scarring and resultant loss of visual acuity.
Stage 4 describes the phase in which stromal melting and further corneal scarring occur. The significant epithelial destruction that ensues during this phase often results in a hyperopic shift.
DLK affects between 2-4% of patients undergoing LASIK surgery.
Patients with DLK often exhibit pain, foreign body sensation, photophobia, and blurry vision.
- Central Toxic Keratopathy
- Infectious keratitis
- Interface fluid
- Corneal haze secondary to increased IOP
- Superficial punctuate keratitis
- Epithelial ingrowth
The exact pathophysiology of DLK remains uncertain. The accumulation of inflammatory infiltrates within the areas of surgical manipulation has led some investigators to postulate that manipulation of the corneal surface may instigate the inflammatory changes that characterize DLK. In fact, the presence of an epithelial defect following a LASIK procedure places the patient at a 24-times greater risk of developing DLK when compared to normal controls.
Intraoperative exposure to inflammatory instigators such as red blood cells, fine sponge fibers, or meibomian gland secretions have also been suggested as playing a role in disrupting corneal epithelial cells during the development of DLK . Further studies are needed to better elucidate the exact mechanism underlying the development of DLK.
Given its inflammatory nature, all stages of DLK typically respond well to corticosteroid therapy. In certain cases irrigation beneath the flap followed by flap repositioning can remove subepithelial infiltrates and minimize complications associated with the condition.
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