PURPOSE: To assess the impact of trabeculectomy, Ex-PRESS shunt and Ahmed valve implantation on biometrical values of the eye. METHODS: The study included 196 patients divided in 3 groups: trabeculectomy (TE) group (n=116), Ex-PRESS shunt (EXP) group (n=28) and Ahmed glaucoma valve (AGV) group (n=52). Each patient underwent optical biometry (keratometry, axial length, anterior chamber depth), autorefractometry (Topcon-8800) intraocular pressure (iCare) and standard ophthalmological examination prior to the surgery, 1 month and 6 months after. Preoperative and postsurgical data were compared to assess biometric values changes. RESULTS: There was a mild decrease of mean keratometry 6 months after AGV implantation (from 44.08+1.06 to 43.94+1.21 D, p=0.023). On the contrary, TE increased corneal refractive power (from 44.39+1.13 to 44.55+1.09 D, p<0.001) 1 month after the surgery. There were no significant changes in EXP group. Steep meridian curvature increases by 0.28+ 0.59 D (p=0.002) 6 months after TE. EXP im