Changes to Corneal Topography and Biometrics After PRESERFLO Microshunt Surgery for Glaucoma

Precis: Glaucoma surgery with PRESERFLO Microshunt shows mild and transient changes in the corneal astigmatism, corneal elevation and biometrics in the early postoperative period. Posterior corneal elevation (PCE) tends to be higher in primary open angle glaucoma (POAG). Purpose: The aim was to determine the changes in the corneal keratometry, astigmatism and elevation, refraction, axial length (AL) and anterior chamber depth and volume after the implantation of the PRESERFLO Microshunt in patients with POAG in the early postoperative period. Patients and Methods: Patients diagnosed with POAG who underwent an ab externo (polystyrene-block-isobutylene-block-styrene) microshunt implantation were recruited. The central corneal thickness, the intraocular pressure (IOP), best-corrected visual acuity, refraction, biometrics, and corneal topography with a Scheimpflug topographer were analyzed preoperatively and 24 hours, 1 week, 1 month, and 3 months after surgery. Results: A total of 30 eyes of 29 patients were included. In 24 eyes the device was implanted as a stand-alone procedure and in 6 eyes it was combined with cataract surgery. The results were analyzed separately. The IOP decreased from 21.8 +/- 5.2 and 16.5 +/- 1.5 mm Hg at baseline to 10.9 +/- 1.8 and 10.1 +/- 1.1 mm Hg at 3 months in the noncombined and combined groups (P<0.01). The anterior surface astigmatism, posterior surface astigmatism, and total corneal astigmatism increased in each group 0.4 +/- 0.3/0.2 +/- 1.0 D, 0.08 +/- 0.1/0.03 +/- 0.1 D and 0.4 +/- 0.3/0.2 +/- 0.9 D, respectively, at 3 months. The anterior corneal elevation and PCE (ACE max, ACE min, PCE max) increased in the first week (P=0.01) with no significant changes at 3 months in the noncombined group. The changes observed in the combined group were not significant. The AL decreased to 0.13 +/- 0.23 and 0.2 +/- 0.07 mm in each group (P=0.01). There was a significant correlation between the IOP and the maximum elevation of the posterior surface of the cornea at the preoperative examination (r=0.93, P=0.02). Conclusions: The PRESERFLO Microshunt implant for glaucoma surgery induces mild and transient changes in corneal astigmatism, AL and anterior chamber depth in the early postoperative period.