This observational study examined eyes undergoing treatments between April 2014 and May 2016 with either the EX-PRESS glaucoma filtration device or trabeculectomy. Trabeculectomies were performed in more than 200 eyes during the study observation period. Eyes selected for inclusion in the study were age and gender matched with the eyes from the EX-PRESS group. Written informed consent for participation in the study was obtained from participants. All procedures and follow-ups took place at the Kagawa University Hospital, Kagawa, Japan. When treatments included both eyes, data from the first eye operated on in the patient was selected and used for the study. The Institutional Review Board of the Kagawa University Faculty of Medicine approved this study protocol. In addition to the standard consent for surgery, all subjects provided written informed consent prior to their enrollment and taking part in the research study.
To be included in the study, patients were required to be older than 20 years of age, and have preoperative uncontrolled IOP despite being administered the maximum tolerated medical therapy. Exclusion criteria included having any significant ocular diseases or history in the operated eye (other than glaucoma or cataract), or exhibiting any other corneal epithelial or stromal disorders that could potentially cause issues during the specular microscopy. The study also excluded patients who did not provide specific reasons on why they were unable to complete the entire 1-year follow-up.
A noncontact specular microscope with an autofocus device, the Tomey EM-3000 (Tomey Corporation, Nagoya, Japan), was used for all observations. All measurements of the endothelial cell count were carried out at the center of the cornea, with the incorporated screen on the device used to visualize the endothelium. The device automatically measured the CECD, with cell density recorded as the number of cells per square millimeter. CECD measurements were obtained prior to and at 6 and 12 months after the surgery. Thereafter, all subsequent measurements were performed every 6 months.
Patients who had a history of vitreous surgery or severe vision loss of their fellow eye underwent the EX-PRESS glaucoma filtration device procedure, with all of the surgeries performed by one surgeon (KH). After administration of retrobulbar anesthesia with lidocaine 2%, all eyes were prepared and draped. In the first step of the procedure, after placing a corneal traction suture (5–0 silk suture), the surgeon dissected a fornix-based conjunctival flap, and then created a one-half thickness scleral flap (approximately 3.5×3.5 mm). Mitomycin C (MMC) was applied to the sclera over the proposed scleral flap site. Subsequently, after positioning 6 to 8 sponges containing 0.04% MMC solution in the subconjunctival space, the sponges were maintained in place for 3 to 5 min. Once the sponges were removed, the area was copiously irrigated using 250 ml of physiologic saline. After removing a block of clear cornea and trabecular meshwork tissue at the edge of the corneoscleral bed, peripheral iridectomy was performed, followed by suturing of the scleral flap using 6 to 7 monofilament 10–0 nylon sutures. Sutures were adjusted to ensure that a small amount of leakage could be observed around the scleral flap margin without causing any shallowing of the anterior chamber.
In the EX-PRESS group, a 26G needle was used to enter the anterior chamber slightly posterior to the blue-gray zone under the scleral flap, and the EX-PRESS (model P50) shunt was introduced into the anterior chamber through the needle track. Suturing of the scleral flap was performed using 2 to 4 monofilament 10–0 nylon sutures, while closure of the conjunctiva used 10–0 nylon sutures at the edges of the incision. For the conjunctiva, one or more of the horizontal mattress sutures were placed centrally. Once the anterior chamber was reformed by using a balanced salt solution, the wound was then checked for leaks. After instillation of a corticosteroid/antibiotic ointment, a sterile eye patch and shield was placed over the eye.
The procedure for the trabeculectomy group used a fornix-based, superior, one site approach, with the cataract surgery (phacoemulsification and intraocular lens insertion) combined with the trabeculectomy. The phacoemulsification procedure in the EX-PRESS group was performed via a 2.4 mm temporal clear cornea incision. After making the incision, the intraocular lens was then placed into the capsular bag. All patients were administered a topical corticosteroid (four times daily) and an antibiotic during the following 8 to 12 weeks after the surgery. If the filtration was judged to be too low by the surgeon or the IOP was too high to meet the target pressure, patients underwent suture lysis with an argon laser under topical anesthesia.
All statistical analyses were performed using SPSS version 19.0 (IBM, New York, NY). CECD and IOP were compared before and after surgery using paired t-tests. A P value less than 0.05 was considered to be statistically significant. Data are presented as the mean ± standard deviation.