Laser reshapes the cornea primarily by using an excimer laser to precisely remove a thin layer of corneal tissue, altering its curvature to improve light focusing.
Understanding Corneal Reshaping with Lasers
The process of reshaping the cornea with a laser, commonly performed in procedures like LASIK (Laser-Assisted In Situ Keratomileusis), involves a highly precise and controlled method to correct refractive errors.
Key Mechanism:
- Excimer Laser Application: The core of corneal reshaping relies on an excimer laser, which is a type of ultraviolet laser. This laser does not cut or burn tissue in the traditional sense; instead, it uses a process called "photoablation" to precisely vaporize microscopic layers of corneal tissue without damaging surrounding areas.
- Tissue Removal: A thin layer of corneal tissue is meticulously removed. The amount and pattern of tissue removed are calculated based on an individual's specific refractive error (e.g., nearsightedness, farsightedness, astigmatism) to achieve the desired vision correction.
- New Cornea Shape: By removing tissue from specific areas of the cornea, the laser gives the cornea a new, more optimal shape. For instance, in treating nearsightedness, the center of the cornea is flattened. For farsightedness, the edges are steepened.
- Improved Light Focus: This newly sculpted corneal surface ensures that light rays entering the eye are focused clearly and directly onto the retina, the light-sensitive tissue at the back of the eye. This results in sharper, clearer vision without the need for glasses or contact lenses.
Impact on the Cornea:
One direct consequence of this tissue removal is that the cornea becomes thinner. Despite this, the procedure is designed to maintain the cornea's structural integrity while achieving the necessary visual correction.
LASIK: A Practical Example
LASIK is a prime example of how laser technology is used for corneal reshaping. It is an outpatient surgical procedure, meaning patients typically return home the same day.
- Before Laser Application: In LASIK, a thin flap is created on the surface of the cornea and gently lifted.
- Laser Reshaping: The excimer laser then applies its pulses to the underlying corneal tissue, removing the precise amount needed to correct the vision.
- Flap Repositioning: After the laser treatment, the corneal flap is carefully repositioned, where it naturally adheres without stitches.
Summary of Laser Reshaping:
| Aspect | Description |
|---|---|
| Laser Type | Excimer laser (ultraviolet laser) |
| Action | Removes a thin layer of corneal tissue |
| Outcome | Gives the cornea a new shape; focuses light clearly on the retina; causes the cornea to be thinner |
| Procedure | Example: LASIK is an outpatient surgical procedure |
This precise and controlled tissue removal is the fundamental mechanism by which lasers effectively reshape the cornea to correct vision.
