Moisture absorbs excimer laser energy and results in less corneal ablation. Therefore, if the laser is applied evenly across the cornea, less ablation will occur centrally because of the moisture, resulting in a central island. Attentiveness to fluid management during the ablation process and central flap compression are surgical techniques that help prevent or reduce central island formation. Also, some laser software programs incorporate a central pretreatment ablation to reduce the incidence of central islands. More fluid accumulates in cases of higher refractive error because of the time and depth of ablation.
Pressure is applied centrally as the instrument is rotated in a circular manner.
The treatment should be applied for 60 seconds, noting striation on the retroilluminated cornea. With photorefractive keratectomy, most central islands resolve spontaneously and do not require surgical intervention. This is because the loss of Bowman's layer stimulates a greater healing response. Surgically, central islands can be treated by lifting the flap and ablating over the area of steepness where the central island is located. Micra USA Inc. The inventor, Nick Caro, MD, from Chicago, has used the Corneal Smoother postoperatively to massage out irregularities of the flap with great success.