ASLA is the only transepithelial singlestep treatment that avoids the eye coming into contact with any instrument. The clinical application of TransPRK, an advanced surface laser ablation (ASLA) treatment, uses the excimer laser to remove the epithelium, resulting in a more precise and more uniform treatment than what is achieved with either manual or alcohol-assisted debridement. ASLA was introduced in September 2009, and since then this treatment has gone through various evolutions. TransPRK-ASLA, performed with the SCHWIND AMARIS laser system, applies an epithelial thickness profile that resembles a slight hyperopic treatment (less than 0.75 D). The resultant epithelium is thinner in the center, hereby avoiding or at least reducing hyperopic shift. Because ASLA applies the laser beam directly over the epithelium, it acts as a smoothing agent for the residual stromal bed.
Treating refractive errors with ASLA has several advantages.
The single-step approach allows simultaneous ablation of the epithelium and the stroma to shorten the overall treatment time and minimize the risk of corneal dehydration. Beside a faster surgical time, epithelial tissue removal has been optimized to avoid myopic-like corrections (approximately -0.75 D). This new approach treats refractive errors by superimposing a defined epithelial thickness profile of approximately 55 µm at the center and 65 µm at the periphery (4 mm radially from center) with a corneal aspheric ablation profile. Additionally, the diameter of epithelial removal is calculated to match the ablation zone, thus decreasing the wound surface and speeding up the healing process.