What is LASIK & Laser Vision Correction?
The cornea is the front part of the eye that provides most of the focusing power for the eyes. This focusing power allows the light rays to converge on the Retina allowing people to see well. In conditions such as myopia or hyperopia, these light rays do not focus properly on the retina. Laser Vision Correction involves gently reshapes the cornea using a precise laser system which allows these light rays to focus on the retina.
The Visual Pathway
To understand laser correction better, we need to understand the visual pathway. Light rays go through a number of structures that help focus the rays on the retina. This light energy is converted into electrical impulses which are then transmitted to the brain. The major structures that the light rays go through are the Cornea and the Lens. The majority of the work in bending the light rays is done by the cornea.
Perfect vision: Light rays go through the cornea and lens and focus on the retina
Myopia (Near-sightedness): Light rays converge in front the retina as the eye in either longer (axial myopia) or the cornea is more steep.
Hyperopia (Farsightedness): Light rays converge behind the retina as the eye is either short (axial hyperopia) or the cornea is too flat.
Astigmatism: Light rays do not all meet in the same plane and thus cause a distorted image if uncorrected. In astigmatism, the cornea is not perfectly spherical but rather is steeper one side and flatter on the other.
Laser Vision Correction Options
a.) Bladeless LASIK
LASIK is an acronym for “Laser-assisted in situ keratomileusis.” It includes all procedures that use the Excimer laser to reshape the cornea.
With completely Bladeless LASIK, the femtosecond laser is used to perform the procedure. LASIK is a two-step process:
- The first step is the creation of a very thin protective flap on the cornea. Until recently, this step was done using a handheld blade keratome. But now, we can create this thin flap using computer-controlled femtosecond laser. The result is a safe, incredibly accurate, and less invasive way to create the flap in the LASIK procedure. This thin flap is customized to each patient and therefore affords another layer of precision. Once the flap is created with the laser, it is lifted and the second step is performed. Because bladeless LASIK allows the surgeon greater precision and predictability in flap creation, each flap can be customized to the patient. The accuracy of the computer controlled flap creation procedure ensures that the correct thickness flap will be created for each patient.
- The second step correcting the vision with the use of the excimer laser. This laser is computer controlled and works in a precise pattern to correct the refractive error. There is a pupil tracker that can move with small movements of the eye which ensures that the procedure (ablation) is centered. In case of a sudden eye movement, the laser stops and the procedure is resume where it stopped when the eye is centered and focused again.
b.) PRK (Photorefractive Keratectomy)
PRK differs from LASIK in that there is no flap creation in the cornea. This can be done for a variety of reason when the creation of flap may not be advisable for the patient. The surgeon usually decides this after examining the patient and looking at the cornea.
The PRK procedure involves numbing the eye with anesthetic drops and then delicately removing the top layer of the cornea called the Epithelium. Then, the computer-controlled excimer laser is then applied directly on the surface of the cornea to reshape the cornea. After the completion of the surgery, a bandage lens is placed for comfort. The top layer, Epithelium, then heals over the next few days. During this time, the patient may experience mild discomfort and light sensitivity.