Laser Vision Correction

PRK (Photorefractive Keratectomy) is a vision correction procedure where the epithelium of the cornea is gently removed from the surface before the laser treatment. Afterwards, a computer-controlled laser ablates the desired portion of the stroma in order to achieve the aimed refractive correction.

LASIK (Laser-Assisted in situ Keratomileusis) is a vision improvement procedure that permanently changes the shape of the cornea by using laser. A mechanical blade device (microkeratome) or alternatively a laser keratome is used to cut a flap in the cornea. The flap is not completely removed but a hinge is left at one end of the flap. The flap is folded back revealing the stroma. Pulses from a computer-controlled laser ablate a calculated portion of the stroma. Then the flap is replaced back.

In LASEK (Laser Epithelial Keratomileusis) procedure, rather than creating a flap with a keratome, the epithelium is removed by loosening it with alcohol and rolled. After the ablation of the desired portion of tissue from the stroma by using computer-controlled laser, epithelial cells are rolled back.

In Epi-Lasik procedure, the epithelium is removed like in Lasek, too. However this is done by an epithelial separator, a plastic oscillating blade. This may prevent epithelial cell death due to reaction with the alcohol. Similar to the other procedures, removal of the epithelium is followed by computer-controlled laser treatment.

PTK (Phototherapeutic Keratotomy) procedure involves photodecomposition of the epithelium where thin layers from it are ablated microscopically by the laser. Corneal scars and opacities e.g. resulted from a trauma or an inactive infection can be etched away by PTK.

It is recommended to treat with laser vision correction:

• In Photo-Refractive Keratectomy (PRK) treatments for the reduction or elimination of mild to moderate myopia of between −1.0D and −8.0D of sphere and less than or equal to −4.0D of astigmatism at the spectacle plane, the combination of which must result in an attempted correction between −0.50D and −10.00D spherical equivalent (SE) at the spectacle plane where sphere or cylinder is at least 1.00D.
• In Laser In-Situ Keratomileusis (LASIK) treatments for the reduction or elimination of myopia (nearsightedness) of less than −10.0D sphere and −0.5D to less than −3.0D of astigmatism at the spectacle plane.
• In Photo-Refractive Keratectomy (PRK) treatments for the reduction or elimination hyperopia between +0.5D and +5.0D sphere at the spectacle plane with refractive astigmatism from +0.5D to +4.0D with a spherical equivalent (SE) of +6.0D.
• In Laser In-Situ Keratomileusis (LASIK) treatments for the reduction or elimination of refractive error of less than +6.0D sphere and −6.0D of cylinder at the spectacle plane (hyperopia with or without astigmatism and mixed astigmatism).

It is not recommended to treat with laser vision correction:

• Patients with age lower than 21 years.
• Patients with systemic diseases that could alter corneal wound healing.
• Patients with dystrophies such as keratoctonus, neo vascularization to within 1 mm of ablation zone.
• Patients with iritis.
• Patients with purely controlled glaucoma.
• Custom aspheric treatments respecting the original asphericity of the cornea
• Patients with keratitis sicca or a previous history of herpic keratitis.
• Pregnant or nursing women.
• Patients who are taking one or both of the following medications: isotretinoin (Accutane); amiodarone hydrochloride (Cordarone).
• Patients who have an autoimmune disease, collagen vascular disease, or an immunodeficiency disease.

Safety and effectiveness of the treatment may not be indicated for patients with diagnosed progressive myopia, ocular disease, corneal abnormality, previous corneal or intra-ocular surgery, or trauma in the ablation zone.

It is not recommended to treat with laser vision correction:

• Patients having insulin dependent diabetes
• Patients having severe allergies
• Patients in whom the residual corneal thickness at the completion of ablation would be less than 400 microns
• Patients with a history of keloid formation (PRK only)
• Patients who are taking the medication Sumatripin (Imitrexc)
• Patients with astigmatism of less than 0.50 diopters
• For PRK refractive treatments greater than −8.0 D of myopia combined with greater than −4.0 D of astigmatism
• For LASIK refractive treatments greater than or equal to −10.0 D of myopia combined with greater than or equal to −3.0 D of astigmatism