Choice of spatial frequency for contrast sensitivity evaluation after corneal refractive surgery

J Refract Surg. Nov-Dec 2001;17(6):646-51.

Abstract

Purpose: To study the utility of measurements of contrast sensitivity at different spatial frequencies as an index of visual recovery following refractive surgery.

Methods: Contrast sensitivity at 1.5, 3, 6, 12, and 18 c/deg was measured with the Stereo Optical FACT chart in 20 patients after photorefractive keratectomy (PRK) using the Nidek EC-5000 excimer laser system, and in 18 patients following laser in situ keratomileusis (LASIK). Contrast sensitivity was measured preoperatively and 1, 3, 6, and 12 months after surgery.

Results: Results showed a statistically significant reduction (P<.01) in contrast sensitivity at all spatial frequencies in PRK patients during the first and third month, but contrast sensitivity recovered to preoperative values by 6 months after surgery (P>.1). In LASIK patients, decreased contrast sensitivity values 1 month after surgery were also obtained at all spatial frequencies. After 3 months, contrast sensitivity at 1.5 and 3 c/deg had recovered and did not differ significantly from preoperative values (P>.1), although contrast sensitivity at other frequencies remained reduced (P<.01). At 6 and 12 months, contrast sensitivity at all spatial frequencies did not differ from that obtained preoperatively (P>.1).

Conclusions: Contrast sensitivity measurements at 6 and 12 c/deg appear to be most useful in the assessment of patients who have undergone laser refractive surgery because defocus and optical aberrations primarily affect the higher spatial frequencies.

Publication types

  • Comparative Study

MeSH terms

  • Adult
  • Contrast Sensitivity / physiology*
  • Cornea / physiopathology
  • Cornea / surgery*
  • Female
  • Humans
  • Keratomileusis, Laser In Situ
  • Lasers, Excimer
  • Male
  • Myopia / physiopathology
  • Myopia / surgery*
  • Photorefractive Keratectomy
  • Time Factors
  • Visual Acuity