The role of patient's age in regression of holmium:YAG thermokeratoplasty-induced correction of hyperopia.

ABSTRACT

PURPOSE: Hyperopic correction can be induced with holmiumYAG laser thermokeratoplasty, which changes corneal curvature by shrinking stromal collagen. The thermal effectiveness of pulsed HoYAG laser depends on the water content of the corneal stroma, which should be related to age. This study investigated the presumed effect of age on the stability of the results of HoYAG laser thermokeratoplasty. METHODS: HoYAG laser thermokeratoplasty was done in 63 eyes of 45 patients for low to moderate hyperopic correction (up to 5 diopters). Patients were treated with one or two rings of 8 spots each, with an optical zone of 6 or 7 mm diameters respectively. RESULTS: Regression of the therapeutic effect was evaluated on the basis of the difference between the attempted to achieved correction ratio on the first postoperative day and at the last visit. The regression ratio was 18% in the patients older than 20 years. Patients younger than 20 years showed a ratio of 48%. Achieved correction was +2.40 D in older patients and +2.05 in younger patients. These values are respectively 43% and 35% of the attempted corrections. CONCLUSIONS: It appears that age-dependent corneal factors do influence the effectiveness of thermal energy on stromal collagen.