[Impairment of mesopic vision following photorefractive keratectomy of myopia].
OBJECTIVE
Halos, glare disability and problems during night driving are significant side effects of photorefractive keratectomy, caused by increasing optical aberrations under reduced conditions of luminiscence. In a previously performed retrospective study an impairment of mesopic vision in most of the investigated eyes was found. To prove these results, a prospective study was conducted.


METHODS
In a prospective, consecutive study mesopic function was investigated in 41 myopic patients, who were interested in PRK. 26 patients underwent surgery (Summit ExciMed UV200LA, optical zone 5 mm), which was performed in 30 eyes. Mesopic function (contrast vision, glare sensitivity) was measured by using the Mesoptometer II test in all 30 eyes preoperatively and 6 to 9 months postoperatively. Additionally, 21 eyes were examined after 12 to 15 months of follow up.


RESULTS
There was a statistically significant reduction of contrast vision and increase of glare sensitivity after 6 to 9 and 12 to 15 months. The Mesoptometer II contrast level of 1:5 (with and without glare) can be used as a critical parameter for the decision, whether mesopic function is markedly 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 contrast 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 12 to 15 months. Whereas 38% of these eyes (with glare 48%) did not recognized the critical contrast level before surgery, this rate increased to 67% (with glare 81%) 12 to 15 months after surgery.


CONCLUSIONS
Impairment of mesopic function has to be considered as a possible side effect of PRK (optical zone 5 mm). Although further investigations are needed, the indication for PRK in special professions (pilots, professional drivers) should be very critical discussed.
Schlote
T
T
Sektion für experimentelle Ophthalmochirurgie, Universitäts-Augenklinik Tübingen.
Derse
M
M
Wannke
B
B
Bende
T
T
Jean
B
B
D000328:Adult; D005260:Female; D006801:Humans; D054018:Lasers, Excimer; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000601:surgery*; D018903:Photorefractive Keratectomy / Q000009:adverse effects*; D011446:Prospective Studies; D014786:Vision Disorders / Q000601:surgery