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Retreatment to enlarge small excimer laser optical zones using combined myopic and hyperopic ablations.

PURPOSE
We describe a retreatment technique using a combination of large-diameter myopic and hyperopic excimer laser ablations of a near equivalent diopter value to enlarge previous small ablation zones without altering the refractive result obtained by the initial surgery.


METHODS
Eight eyes of six patients were retreated with a Technolas Keracor 217 laser in order to enlarge the optical zone. All patients had a good refractive result after the initial surgery, but reported halos under low light conditions. Retreatment consisted of a combination of myopic and hyperopic ablations of near equivalent value, eg, -1.00 D and +1.00 D treatment. These opposite value ablations should neutralize their respective refractive effect, but by removing a larger diameter of tissue, actually displace the transition zones further toward the corneal periphery. Although the initial treatment used photorefractive keratectomy in four of the eight eyes, LASIK was used for retreatment in all eyes. Improvement was assessed subjectively by the patient and was measured objectively with a Technomed C-Scan ray-tracing program.


RESULTS
In six of eight eyes, patients experienced moderate or marked improvement. This improvement was objectively correlated on postoperative corneal topography.


CONCLUSION
Combined larger diameter myopic and hyperopic retreatment seems to be safe and effective for enlarging previous small treatment zones, reducing symptoms such as halos in selected patients.