Assessment of contrast sensitivity and aberrations after photorefractive keratectomy in patients with myopia greater than 5 diopters

ABSTRACT

This study aimed to assess changes in contrast sensitivity and aberrations in cases of myopia greater than 5.0 diopter [D] who had photorefractive keratectomy [PRK]. In this semi-experimental study, 20 eyes of ten patients were studied. Inclusion criteria were at least 5.0 D of myopia, stable refraction in the past year, no history of refractive surgery, a minimum corneal thickness of 480 micro m, and having surgery in both eyes. Exclusion criteria were the presence of any corneal condition. In addition to the routine tests, aberrometry and assessment of contrast sensitivity was done using the WaveLight Allegro Analyzer and the VectorVision CSV-1000. After PRK using the Concerto Excimer Laser [WaveLight, Alcon], patients were scheduled to have follow-up visits at 1 month, 3 months, and 1 year after surgery. Contrast sensitivity with glare showed an increasing trend only at the spatial frequency of 3 cycles per degree [cpd] [P=0.013]. Contrast sensitivity without glared increased postoperatively at special frequencies of 3, 6, and 18 cpd [P<0.05]. The preoperative level of higher order aberrations root mean square [HOA RMS] of 0.24 +/- 0.08 reached 0.71 +/- 0.25 at 12 months after surgery. Assessment of comma and trefoil showed no significant difference between preoperative and postoperative values, but the amount of spherical aberration changed from a mean preoperative value of 0.0 +/- 0.09 to 0.27 +/- 0.15 at 12 months after surgery. In the treatment of myopia greater than 5.0 D, PRK with the Concerto Excimer Laser can improve contrast sensitivity in certain spatial frequencies. This is while HOA RMS and spherical aberration increase.