Estimating the Preoperative Corneal Power With Scheimpflug Imaging in Eyes That Have Undergone Myopic LASIK

J Refract Surg. 2016 May 1;32(5):332-6. doi: 10.3928/1081597X-20160225-03.


Purpose: To investigate whether the Estimated Pre-Refractive SimK accurately predicts the preoperative corneal power (K) in eyes with previous myopic femtosecond laser-assisted LASIK (FS-LASIK) and whether a better prediction can be developed.

Methods: Preoperatively and 3 months after FS-LASIK, patients underwent anterior segment imaging with the Pentacam HR rotating Scheimpflug camera (Oculus Optikgeräte, Wetzlar, Germany). Posterior and anterior corneal curvature and power and asphericity (Q-value at 8 mm) were recorded. Multiple linear regression was used to assess the relationship among variables.

Results: One hundred four eyes of 104 patients were enrolled. The Estimated Pre-Refractive SimK (43.19 ± 1.63 diopters [D]) was lower (P = .0014) than the mean preoperative K (43.44 ± 1.49 D). The difference was within ±0.50 and ±1.00 D in 53.8% and 86.5% of eyes, respectively. Multiple linear regression detected a statistically significant relationship (r(2) = 0.8497, P < .0001) among the investigated parameters: preoperative anterior corneal radius = 1.156 + 1.012 * postoperative posterior corneal radius - 0.3800 * postoperative Q-value. When this equation was used to predict the preoperative K, the difference between the actual preoperative K and the predicted value (43.41 ± 1.38 D) was not statistically significant. The rate of eyes with a difference between the predicted and actual preoperative K within ±0.50 and ±1.00 D increased to 61.5% and 93.3%, respectively.

Conclusions: The corneal power before FS-LASIK can be accurately predicted from the postoperative corneal measurements of a rotating Scheimpflug camera. The multiple regression formula described may be more accurate than the Estimated Pre-Refractive SimK available on the Pentacam. [J Refract Surg. 2016;32(5):332-336.].

MeSH terms

  • Adult
  • Aged
  • Cornea / physiopathology*
  • Diagnostic Imaging / methods
  • Diagnostic Techniques, Ophthalmological*
  • Female
  • Humans
  • Keratomileusis, Laser In Situ / methods*
  • Lasers, Excimer / therapeutic use*
  • Lens Implantation, Intraocular
  • Male
  • Middle Aged
  • Myopia / physiopathology
  • Myopia / surgery*
  • Optics and Photonics
  • Preoperative Period
  • Prospective Studies
  • Refraction, Ocular / physiology*
  • Young Adult