New parameters for evaluating corneal biomechanics and intraocular pressure after small-incision lenticule extraction by Scheimpflug-based dynamic tonometry

Purpose To evaluate parameters and dynamic corneal densitometry with a new dynamic Scheimpflug analyzer (Corvis ST) in eyes having small-incision lenticule extraction (SMILE). Setting Qvision, Vithas Virgen del Mar Hospital, Almeria, Spain. Design Retrospective case series. Methods The study comprised eyes from the same institution having small-incision lenticule extraction surgery. Preoperative and 1-month postoperative measurements were taken. Results Forty-three eyes were evaluated. The mean difference in intraocular pressure (IOP) and biomechanically corrected IOP before and after surgery was 2.24 mm Hg ± 1.26 mm (SD) ( P  = .001) and 0.57 ± 1.77 mm Hg ( P  = .04), respectively. All dynamic Scheimpflug analyzer parameters changed significantly after surgery ( P P P  = .15). None of the 4 dynamic corneal densitometry parameters changed significantly as a result of surgery ( P  ≥ .29). A new sign, described as an inclined brightness fringe moving through the corneal periphery, appeared preoperatively in eyes with higher dynamic corneal densitometry. This sign was more prevalent postoperatively (48.8% versus 72.1%) ( P  = .04). Conclusions The biomechanically corrected IOP measured after surgery with the dynamic Scheimpflug analyzer showed better agreement with the preoperative values than IOP. The stiffness parameter was not dependent on the amount of removed corneal thickness. A new sign correlated with dynamic corneal densitometry was found and might be related to changes in corneal hydration and biomechanics.