Corneal Biomechanical Changes Following Trabeculectomy, Phaco-trabeculectomy, Ahmed Glaucoma Valve Implantation and Phacoemulsification

Purpose: to determine corneal biomechanical changes following major glaucoma procedures. methods: in a prospective comparative case series, corneal biomechanical properties were assessed using the ocular response analyzer (ora, reichert inc., depew, new york, usa) before and 3 months after surgery in 89 eyes of 89 patients undergoing trabeculectomy + mitomycin c (mmc) (23 eyes, group 1), phacotrabeculectomy + mmc (23 eyes; group 2), ahmed glaucoma valve (agv) implantation (17 eyes; group 3) or phacoemulsification (pe) alone (26 non-glaucomatous eyes; group 4). patients with history of contact lens use, previous intraocular surgery, any chronic corneal disease, central corneal thickness ≥580 microns or ≤500 microns, post-operative intraocular pressure (iop) > 21 mmhg or ≤ 5 mmhg, and any surgical complication were excluded. main outcome measures included changes in corneal hysteresis (ch) and corneal resistance factor (crf). results: preoperatively, ch was lower in glaucomatous versus non-glaucomatous eyes (5.4, 5.3, 5.2 and 8.1 mmhg in groups 1, 2, 3 and 4 respectively, p<0.001). three months after surgery, mean ch increased by 2.16, 2.29 and 2.30 mmhg in groups 1, 2 and 3 respectively (p<0.001) but only by 0.11 mmhg in group 4 (p=0.704). the postoperative increase in ch in glaucomatous eyes was more significant when iop was reduced by more than 10 mmhg. crf also showed a significant increase in all study groups postoperatively (p<0.001). conclusion: ch and crf increased significantly 3 months after glaucoma procedures. alterations in corneal biomechanical properties should be considered when measuring iop after successful glaucoma surgery.