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, Almería, 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 < .05). The variation in each parameter was correlated with the removed corneal thickness (P < .05), except the stiffness parameter at the first applanation (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.