- Photorefractive Keratectomy or PRK
- Advanced Surface Treatment (AST)
In these procedures the corneal stroma, the part that is reshaped with the laser, is exposed by removing the overlying layer of epithelium.
These procedures are known for their post operative discomfort lasting for 3 to 4 days following the surgery. Also the visual recovery may take longer than that of LASIK
The flapless procedures come with the advantage of being more tissue sparing than LASIK
, and are thus reserved for patients who have preoperative corneal thickness that is deemed on the low range of normal.
In Epi-Lasik, the epithelim is moved out of the way as a sheet using a blunt vibrating blade called the epikeratome.
During Epi-LASIK the sheet of epithelium is redraped over the treated stroma, immediatly following the Excimer laser correction
. Theoretically the replaced epithelium serves as a bandage and promotes healing.
However, experience shows that this method is not any less uncomfortable and does not provide for faster visual recovery than PRK and has thus fallen out of favor.