Changes in Aqueous Humor pH After Femtosecond Laser-Assisted Cataract Surgery

PURPOSE: To compare aqueous humor pH values in patients during femtosecond laser-assisted cataract surgery with patients during conventional phacoemulsification. METHODS: A prospective clinical study was conducted in 29 eyes of 29 patients who underwent cataract surgery by a single surgeon. The femtosecond laser group included 15 eyes operated on with a femtosecond laser platform (Catalys; Abbott Medical Optics, Santa Ana, CA) and the phacoemulsification group included 14 eyes that were operated on with conventional phacoemulsification. The femtosecond laser group was subdivided into low, medium, and high level of cavitation gas bubbles after docking and the femtosecond laser procedure, according to the judgment of the surgeon. Aqueous humor samples (0.10 to 0.15 mL) were collected through a paracentesis from each patient after docking, corneal incisions, and nucleus fragmentation in the femtosecond laser group and after corneal incisions but before injection of viscoelastic in the phacoemulsification group, then analyzed with a pH meter. RESULTS: The mean pH was 6.53 ± 0.09 (range: 6.42 to 6.70) and 7.42 ± 0.07 (range: 7.28 to 7.48) in the femtosecond laser and phacoemulsification groups, respectively ( P < .001). In the femtosecond laser group, no significant differences in pH were observed between the three subgroups after docking and the femtosecond laser surgical procedure: low (6.55 ± 0.09 [range: 6.53 to 6.57]), medium (6.54 ± 0.07 [range: 6.52 to 6.55]), and high (6.42 ± 0.00 [range: 6.40 to 6.44]) level of gas bubbles. CONCLUSIONS: Cavitation bubbles derived from the photodisruption process in femtosecond laser-assisted cataract surgery lead to an acidic shift of the aqueous humor pH as a result of the transformation of carbon dioxide to carbonic acid. The level of gas bubbles visible after the laser photodisruption does not seem to correlate with this pH shift. Further analysis of femtosecond laser-assisted cataract surgery is necessary. [ J Refract Surg. 2015;31(7):462–465.]