title: Measurement of radial keratotomy clear zone diameters.
abstract: BACKGROUND
  To compare the accuracy of photographic measurements to slit-lamp measurements of radial keratotomy clear zone diameters in order to develop an independent, objective, unbiased, and reproducible method of verifying clinical observations.
  
  
  METHODS
  Twenty-five patients (48 eyes) following radial keratotomy had matched slit-lamp and photographic measurements of the diameter of the central clear cornea between the ends of opposite radial incision pairs. Matched slit-beam, photographic, and pathologic observations were compared statistically.
  
  
  RESULTS
  Two hundred fifty-four slit-lamp clear zone diameter measurements were obtained. In twenty instances (8%), the radial incision end-point could not be identified on the photograph. For the remaining 234 measurements, the mean slit-lamp clear zone diameter was statistically smaller than the photographic measurement by 0.03 mm (t-test, p = 2.2 x 10(-5)). The slit-lamp and photographic clear zone measurements were strongly positively correlated (Pearson r = 0.99, p < 1.0 x 10(-15)). Matched slit-lamp, photographic, and pathologic clear zone measurements (N=8) in one excised corneal button were not statistically different.
  
  
  CONCLUSIONS
  For radial keratotomy clear zone diameters, slit-beam measurements and photographic caliper measurements yield indistinguishable results that are highly concordant over a wide range of diameters. Both slit-beam and photographic measurements yield accurate and reliable results that reflect the true pathologic achieved clear zone diameter following radial keratotomy surgery.
authors.affiliation: Bascom Palmer Eye Institute, The University of Miami, School of Medicine, Florida 33418, USA.
authors.forename: M R
authors.initials: MR
authors.lastname: Grimmett
authors.forename: G S
authors.initials: GS
authors.lastname: Ogawa
mesh_terms: D003315:Cornea / Q000473:pathology* / Q000601:surgery*; D003941:Diagnostic Techniques, Ophthalmological; D006801:Humans; D007646:Keratotomy, Radial; D010781:Photography; D054140:Refractive Surgical Procedures; D015203:Reproducibility of Results; D013537:Sutures