TREATMENT OF HALOS AFTER PHOTOREFRACTIVE KERATECTOMY

BACKGROUND: Some patients, despite a good visual outcome after photore fractive keratectomy (PRK), have severe problems with halos. METHODS: Ten eyes with a near-piano refraction after PRK were treated again wit h PRK to reduce halos. The goal of the second surgery was to enlarge t he diameter of the treatment zones without changing the refraction obt ained by the first surgery. The treatment zone was enlarged from 5 or 6 mm to 7 mm. In eyes in which a multizone technique was used in the f irst PRK, the amount of correction was increased in the transition zon e. However, the refractive power in the central 4 or 5-mm zone was not altered. This result was obtained by calculating the amount of desire d increased correction on a large zone (6 or 7 mm) and then for the sa me amount on a smaller zone (4 or 5 mm). The latter, which would produ ce changes of curvature in the central zone, is subtracted from the ov erall treatment. Only the part of the treatment where the laser beam i ncreased from 4 or 5 mm to 6 or 7 mm was delivered to the eye. In this process, only the peripheral zones were modified. The central 4 or 5 mm zone was deepened but its curvature and the refraction remained the same. RESULTS: A decrease of symptoms was noticed by seven of the ten patients. In all eyes, the refraction obtained by the initial surgery was not significantly changed by the second surgery. The best results were obtained in milder myopic patients who had their first surgery w ith a small diameter ablation zone. CONCLUSION: Halos can be reduced b y repeating the PRK and by increasing the treatment zone without chang ing the refraction obtained by the first PRK.