Comparison of objective and subjective refractive surgery screening parameters between regular and high-resolution Scheimpflug imaging devices

J Cataract Refract Surg. 2015 Feb;41(2):286-94. doi: 10.1016/j.jcrs.2014.06.026. Epub 2014 Dec 20.


Purpose: To compare objective and subjective metrics from regular and high-resolution Scheimpflug devices (Pentacam) to determine their equivalence and interchangeability for refractive surgery screening.

Setting: Emory Vision at Emory University, Atlanta, Georgia, USA.

Design: Retrospective comparative case series.

Methods: Eyes of consecutive screened refractive surgery patients were evaluated with high-resolution and regular Scheimpflug devices. Objective parameters evaluated included keratometry (K) values, central corneal thickness (CCT), and device-generated keratoconus screening indices. Masked expert reviewers subjectively graded images as normal, suspicious, or abnormal.

Results: One hundred eyes of 50 patients were evaluated. The mean K values were not significantly different (anterior K: high resolution 1.21 diopters [D] ± 1.13 (SD) versus regular 1.15 ± 1.16 D, P = 0.73; posterior K: 0.34 ± 0.23 D versus regular 0.35 ± 0.23 D, P = .67). The mean CCT was significantly thinner in the high-resolution group (514.7 ± 26.6 μm versus 527.6 ± 27.6 μm (P < .0001) with limits of agreement of -12.9 to +17.5 μm. Most keratoconus screening indices were more suspicious with the high-resolution device than with the regular device except the indices of height asymmetry and height deviation. Subjectively, 60% of cases received the same score, high resolution was more suspicious in 28% of cases, and regular was more suspicious in 12% of cases; there was only slight subjective agreement between technologies (κ = 0.26 to 0.31).

Conclusions: Regular and high-resolution Scheimpflug imaging devices generated different objective values and significantly different subjective interpretations with poor inter-reviewer agreement. The high-resolution device provided a more conservative overall output. For refractive surgical screening, the 2 devices are not interchangeable.

Financial disclosure: Proprietary or commercial disclosures are listed after the references.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Cornea / pathology*
  • Corneal Pachymetry
  • Corneal Surgery, Laser*
  • Corneal Topography
  • Diagnostic Imaging / methods*
  • Diagnostic Techniques, Ophthalmological* / instrumentation
  • Female
  • Humans
  • Keratoconus / diagnosis*
  • Male
  • Middle Aged
  • Observer Variation
  • Photography
  • Refractive Errors / diagnosis*
  • Retrospective Studies
  • Tomography, Optical Coherence
  • Young Adult