Clinical evaluation of a new correction algorithm for dynamic Scheimpflug analyzer tonometry before and after laser in situ keratomileusis and small-incision lenticule extraction

J Cataract Refract Surg. 2018 May;44(5):581-588. doi: 10.1016/j.jcrs.2018.01.023. Epub 2018 Apr 22.

Abstract

Purpose: To compare a biomechanically corrected intraocular pressure (bIOP) algorithm provided by the dynamic Scheimpflug analyzer (Corvis ST) with Goldmann applanation tonometry IOP (Goldmann IOP) and standard dynamic Scheimpflug analyzer IOP measurements before and after laser in situ keratomileusis (LASIK) and refractive lenticule extraction small-incision lenticule extraction (SMILE) surgeries.

Setting: Smile Eye Clinic, Munich, Germany, and University of Liverpool, Liverpool, United Kingdom.

Design: Retrospective case series.

Methods: Patients scheduled for LASIK and patients scheduled for small-incision lenticule extraction for myopia or myopic astigmatism were included. The preoperative and postoperative evaluations included Goldmann, Scheimpflug tomography, and dynamic Scheimpflug analyzer IOP measurements.

Results: The study comprised 14 patients in the LASIK group and 22 patients in the small-incision lenticule extraction group. Preoperative Goldmann IOP and Scheimpflug analyzer IOP values showed significant positive correlation with central corneal thickness (CCT) (P = .05 for LASIK; P = .003 for small-incision lenticule extraction). No significant correlation was found between bIOP and CCT (P > .05). After both surgeries, there were significant decreases in Goldmann IOP (-3.2 mm Hg ± 3.4 [SD] and -3.2 ± 2.1 mm Hg, respectively; both P < .001) and Scheimpflug analyzer IOP (-3.7 ± 2.1 mm Hg and -3.3 ± 2.0 mm Hg, respectively, both P < .001) compared with preoperative readings, whereas bIOP did not differ significantly (0.1 ± 2.1 mm Hg and 0.8 ± 1.8 mm Hg, respectively; P = .80 and P = .273, respectively).

Conclusions: The bIOP readings before and after LASIK and small-incision lenticule extraction were neither significantly different nor correlated with CCT. In contrast, both Goldmann IOP and Scheimpflug analyzer IOP had significant reductions postoperatively and showed significant correlation with CCT preoperatively.

MeSH terms

  • Adult
  • Algorithms*
  • Corneal Stroma / pathology
  • Corneal Stroma / surgery*
  • Corneal Topography
  • Equipment Design
  • Female
  • Follow-Up Studies
  • Humans
  • Intraocular Pressure / physiology*
  • Keratomileusis, Laser In Situ / methods*
  • Lasers, Excimer / therapeutic use*
  • Male
  • Middle Aged
  • Myopia / diagnosis
  • Myopia / physiopathology
  • Myopia / surgery*
  • Postoperative Period
  • Preoperative Period
  • Retrospective Studies
  • Tonometry, Ocular / instrumentation*