LASIK (Laser-Assisted in Situ Keratomileusis) is a widely performed refractive procedure that corrects common vision problems like nearsightedness, farsightedness, and astigmatism. The procedure involves reshaping the clear, dome-shaped tissue at the front of the eye, known as the cornea. LASIK typically does not result in a visible or functionally significant scar composed of fibrotic tissue.
How the Cornea Heals Without Scarring
The cornea is composed of five distinct layers. The unique surgical technique of LASIK is designed to minimize trauma that would trigger a severe healing response. Unlike injuries that penetrate the full depth of the tissue, LASIK focuses on the thick middle layer, the corneal stroma, while preserving the outer layer. The excimer laser removes microscopic amounts of tissue from the stroma to correct the refractive error.
Before the laser reshapes the stroma, a microkeratome or a femtosecond laser creates a thin, hinged flap from the outer corneal layers. This flap, which contains the protective epithelial layer, is gently lifted and then immediately repositioned after the laser treatment. The flap serves as a natural bandage that covers the treated stromal bed.
This immediate replacement of the epithelial layer allows for rapid, scarless surface healing. Epithelial cells quickly migrate to seal the flap’s edges, preventing the inflammatory and fibrotic response that leads to a dense, opaque scar. The precision of the modern excimer laser also contributes by removing tissue without causing the collateral thermal damage that often initiates a wound healing cascade.
Distinguishing Corneal Haze from Scarring
The most common confusion regarding post-LASIK visual opacity is the difference between true scarring and corneal haze. A true scar (fibrosis) is a permanent, disorganized deposition of collagen that interferes with light transmission and typically requires surgical intervention. This type of severe scarring is extremely rare after LASIK.
Corneal haze, in contrast, is a temporary, superficial clouding of the stroma resulting from an overactive healing response. This mild opacity is caused by the activation of keratocytes, the resident corneal cells. These cells transform into myofibroblasts and deposit new, slightly disorganized collagen. This transient response often resolves on its own as the eye heals over several months.
When haze occurs in LASIK, it is typically mild and localized to the edges or the interface of the flap. Surface ablation procedures like Photorefractive Keratectomy (PRK) carry a higher risk of temporary haze. This is because PRK involves the complete removal of the protective epithelial layer. The lack of the epithelial bandage triggers a more pronounced keratocyte activation, resulting in a more significant haze that is sometimes managed with anti-scarring agents like Mitomycin C.
The Long-Term Visibility of the LASIK Flap
Once the initial healing period is complete, the cosmetic and structural outcome of LASIK is excellent. The incision line defining the edge of the corneal flap is microscopic and virtually invisible to the naked eye. While a specialized eye doctor can identify the flap interface under high magnification using a slit lamp, the eye maintains a structurally normal appearance.
The healing process involves strong adhesion between the replaced flap and the underlying stromal bed, with the flap regaining stability over time. The procedure does not alter the cosmetic appearance of the eye, and the cornea remains clear and unscarred. Although the flap interface is not as strong as the original tissue, the healed cornea is robust for all normal daily activities.