Impairment of mesopic vision by photorefractive keratectomy of myopia

Purpose Halos, glare disability and problems during night driving are signi ficant side effects of photorefractive keratectomy. caused by increasing op tical aberrations under reduced conditions of luminiscence. In a previously performed retrospective study an impairment of mesopic vision in most of t he investigated eyes was found. To prove these results, a prospective study was conducted. Methods and patients In a prospective, consecutive study mesopic function w as investigated in 41 myopic patients, who were interested in PRK. 26 patie nts underwent surgery (Summit ExciMed UV200LA, optical zone 5mm), which was performed in 30 eyes. Mesopic function (contrast vision, glare sensitivity ) was measured by using the Mesoptometer II test in all 30 eyes preoperativ ely and 6 to 9 months postoperatively. Additionally, 21 eyes were examined after 12 to 15 months of follow up. Results There Tvas a statistically significant reduction of contrast vision and increase of glare sensitivity after 6 to 9 and 12 to 15 months. The Me soptometer II contrast level of 1:5 (with and without glare) can bt: used a s a critical parameter for the descision, whether mesopic function is marke dly reduced or not. Before surgery, contrast level of 1:5 without glare was not recognized in 30%, with glare in 40%, After 6 to 9 months, this contra st level was not recognized in 73% of the 30 eyes without glare, with glare in 80%. Out of these 30 eyes, 21 eyes were followed over 1? to 15 months. Whereas 38% of these eyes (with glare 48%) did not recognized the critical contrast level before sugery, this rate increased to 67% (with glare 81%) 1 2 to 15 months after surgery. Conclusions Impairment of mesopic function has to be considered as a possib le side effect of PRK (optical zone 5 mm). Although further investigations are needed, the indication for PRK in special professions (pilots, professi onal drivers) should be very critical discussed.