Keratometric values changes following different types of glaucoma procedures

PURPOSE: To assess keratometric changes after trabeculectomy (TE), Ex-PRESS shunt (EXP) and Ahmed glaucoma valve (AGV) implantation.

METHODS: The study included 196 patients divided in 3 groups: TE group (n=116), EXP group (n=28) and AGV group (n=52). Each patient underwent keratometry (Topcon-8800) and corneal topography (Tomey RT-7000) proir to the surgery, 1 month and 6 months after intervention. Preoperative and postsurgical data were compared to assess keratometric values changes.

RESULTS: Corneal astigmatism (CA) magnitude increased by 0.3 D 6 months after TE and EXP. There was a significant correlation between CA magnitude and uncorrected visual acuity (UCVA) in TE and EXP groups (r=-0.497, p=0.002; r=-0.405, p=0.006, respectively). AGV implantation did not lead to significant changes in CA magnitude. Steep corneal meridian increased from 44.79±1.79 to 45.08±1.12 D  (p=0.002) 6 months after TE. EXP implantation decreased flat meridian from 44.28±1.01 to 44.0±1.09 D (p=0.002). There was a decrease of flat corneal meridian from 43.59±1.04 to 43.44±1.19 D (p=0.036), as well as a change of the steep meridian axis from 88.6±50.5 to 71.4±48.9 deg (p=0.057) in AGV group.

CONCLUSION: Decline of UCVA is associated with an increased CA magnitude after TE and EXP. Thus, patients should be informed that prescribing new spectacles or toric intraocular lens implantation due to upcoming phacoemulsification is a frequent perspective after these types of glaucoma procedures. Nevertheless, AGV implantation has no significant impact on CA magnitude and does not affect UCVA.

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