SBK Vision Correction Surgery: Is It Superior to LASIK and PRK?
By Sophie Brink
Published on November 17, 2007
In an ambitious attempt to provide an alternative to LASIK and PRK, surgeons have developed a new type of refractive surgery called SBK, or sub-Bowman's keratomileusis. The procedure treats the refractive errors that cause myopia (nearsightedness), hyperopia (farsightedness), and astigmatism.
LASIK is the most commonly performed laser vision correction today because it boasts a shorter healing period than PRK. During the LASIK procedure, the surgeon creates a flap in the outer eye. He or she then folds back the flap to reveal the underlying corneal tissue. After using an excimer laser to reshape the cornea, the surgeon replaces the flap.
PRK remains a good alternative for many vision correction patients who are good candidates for LASIK, including those who have thin corneas. During PRK, the outermost layer of the cornea, the epithelium, is removed, allowing the surgeon to reshape the tissue underneath. The downside of PRK, however, is that it results in a longer recovery period, and special contact lenses must be worn to promote epithelial growth.
SBK vs. LASIK and PRK
SBK is similar to LASIK in that it involves the creation of a corneal flap, and an excimer laser is used to sculpt the underlying tissue. In SBK, however, the surgeon cuts a thinner flap. Whereas traditional LASIK flaps have a thickness ranging between 120 to 160 microns, the SBK flap is approximately 110 microns thick. The new procedure is called "sub-Bowman's keratomileusis" because the surgeon cuts only deep enough to include the thin layer of the cornea known as Bowman's membrane.
The thinner SBK flap not only is ideal for those with thinner corneas, but also minimizes the risk of dry eye. According to a study by Dr. Eric D. Donnenfeld, post-surgical dry eye is associated with the amount of nerve endings that are damaged during the process of creating a flap. The SBK flap is not only thinner, but smaller in diameter than that of its LASIK counterpart, thus reducing the amount of nerves that are severed in its creation. SBK also may carry a lesser risk of corneal ectasia compared to LASIK because the smaller SBK flap causes less damage to the corneal fibers that help the cornea to preserve its shape.
Although SBK may seem like a miracle alternative to LASIK, there are refractive surgeons who will hasten to dispel that notion. Since cutting into Bowman's membrane can lead to complications such as hazing or scarring, some surgeons wonder whether the benefits of SBK outweigh the possible risks.