Purpose: To investigate the correlation between environmental changes in ultraviolet (UV) radiation levels and the incidence of late-onset cornea haze (LOCH) after photorefractive keratectomy (PRK).
Setting: SynsLaser Clinic, Tromsø, Norway.
Methods: The study comprised 404 eyes that had myopic PRK and photoastigmatic refractive keratectomy from February 1996 through July 1998. The high latitude (70 degrees N) of the observation site provided "natural laboratory" conditions to look at the occurrence of LOCH with high and low UV-radiation levels, which occurred during summers and winters, respectively. The diagnostic criterion for LOCH was acute haze of grade > or =2 occurring between 4 and 12 months postoperatively.
Results: The follow-up ranged from 12 to 41 months. Of the 314 eyes that met the inclusion criteria, 11 developed LOCH when the environmental UV-radiation level was high. No eye developed LOCH when the level was low. The correlation between a high level of environmental UV radiation and the occurrence of LOCH was statistically significant (P =.001).
Conclusion: Environments with high UV-radiation levels may increase the risk of LOCH after PRK in eyes with moderate to high myopia. Use of UV-protective eyewear should be encouraged during the first year after PRK.