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The corneal stroma is the part of the cornea that is re-shaped in laser eye surgery. Some of the biggest differences between laser eye surgeries are in how the stroma is exposed in order to apply the laser to it and ablate (vaporise) some of the tissue. In LASIK, a flap of tissue comprising epithelium, Bowman's PLUS a considerable part of the stroma is cut and lifted and the laser is applied to the stroma remaining under the flap before the flap is replaced. In surface ablation techniques (LASEK, epi LASIK, PRK, transepithelial PRK) the epithelium is removed temporarily or permanently and the laser is applied to the top of the stroma.
In LASIK, which penetrates deeper than any other laser eye surgery, the amount of stroma that is not compromised (i.e. not removed with the laser and not part of the flap; usually referred to as the residual stromal thickness) becomes a material issue, because if too much tissue is compromised it can lead to instability of the cornea and a condition called ectasia. |
