Role of clearance and treatment zones in contrast sensitivity: Significance in refractive surgery

Brian S.Boxer Wachler, Daniel S. Durrie, Kerry K. Assil, Ronald R. Krueger

Research output: Contribution to journalArticlepeer-review

39 Scopus citations


Purpose: To evaluate the relationship between contrast sensitivity, surgical treatment zone, and clearance (ablation or clear zone - pupil diameter) in photorefractive keratectomy (PRK) and radial keratotomy (RK). Setting: Saint Louis University Eye Institute, St. Louis, Missouri, and Hunkeler Eye Center, Kansas City, Missouri, USA. Methods: Thirteen patients and PRK and 20, RK. Contrast sensitivity was measured with the Stereo Optical F.A.C.T. (F.A.C.T) and VectorVision CSV-1000 (VV) charts. Pupils were measured with the Rosenbaum card. Results: In the PRK group, VV contrast sensitivity at 6 and 12 cycles per degree (cpd) correlated with the ablation zone (r2 = 0.18 and 0.22, respectively), while visual acuity and F.A.C.T. contrast sensitivity did not correlate. In the RK group, both VV and F.A.C.T. contrast sensitivity at 6 cpd correlated with clearance (r2 0.29 and 0.12, respectively). Pupils were larger with the VV test than with the F.A.C.T. chart because ambient chart luminance was less in the former. Conclusion: Contrast sensitivity is likely a more sensitivity indicator of visual function than acuity in refractive surgery. The VV system unmasks aberrations from the transition zone of ablated and unablated cornea in PRK. Larger samples are needed to determine the critical ablation clearance of the pupil to avoid loss of visual function.

Original languageEnglish (US)
Pages (from-to)16-23
Number of pages8
JournalJournal of cataract and refractive surgery
Issue number1
StatePublished - 1999
Externally publishedYes

ASJC Scopus subject areas

  • Surgery
  • Ophthalmology
  • Sensory Systems


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