Refractive and Corneal Astigmatism After Canal-Based Microinvasive Glaucoma Surgery in the Mid-Term

To evaluate the mid-term impact of Hydrus Microstent implantation on refractive and corneal astigmatism.

Eyes undergoing Hydrus Microstent implantation were retrospectively collected. Subjective refraction was required at baseline and at 3 and 12 months postoperatively. Corneal tomography was optional (Pentacam, OCULUS Optikgeräte GmbH, Wetzlar, Germany). Astigmatism was analyzed using three-dimensional power vector analysis.

Forty-two eyes of 35 patients were implanted with a Hydrus Microstent, including 15 eyes treated as a stand-alone procedure and 27 eyes combined with phacoemulsification. In the overall cohort, mean refractive cylinder remained stable from baseline (C_D0 = -1.27 ± 0.94 D) to 3 months (C_D90 = -1.33 ± 1.29 D, p = 0.6) and 12 months (C_D360 = -1.48 ± 1.33 D, p = 0.08). Blurring strength vector B was stable between 3 and 12 months (p = 0.8; p_{Phacoemulsification} = 0.7; p_Stand-alone >0.9). None of the power vector components J₀ and J₄₅ showed significant effects of time, group, or their interaction in any cohort. Tomography data were available for 20 eyes of 18 patients, with half undergoing stand-alone implantation. J₀, J₄₅, and B of both anterior and posterior surface astigmatism remained stable over time, with no significant effects of surgical group or of the interaction between group and time.

Hydrus Microstent implantation does not affect corneal and refractive astigmatism after 12 months.