Relationship between Tube Parameters and Corneal Endothelial Cell Damage after Ahmed Glaucoma Valve Implantation: A Comparative Study

Abstract

Purpose: We compared the clinical factors, including anterior chamber tube parameters, in patients with and without corneal endothelial cell damage after Ahmed glaucoma valve (AGV) implantation. Methods: In this retrospective and comparative case series, patients who underwent AGV implantation were enrolled consecutively. Serial specular microscopy was performed before and after AGV implantation. Patients were divided into two groups depending on whether there was a significant decrease in corneal endothelial cell density (ECD), which was determined by each patient’s rate of ECD change (%/year), calculated using linear regression analyses. Tube parameters such as the tube-cornea distance (TCD) and tube-cornea angle (TCA) were measured with anterior segment optical coherence tomography. Clinical factors related to the rate of ECD change were evaluated with regression analyses and compared between the two groups. The tipping point at which tube parameters became significantly associated with the rate of ECD change was identified with broken stick regression analyses. Results: There were 30 eyes (32.3%) with ECD damage (group 1) and 63 eyes (67.7%) without damage (group 2). The mean rate of ECD change (%/year) was −18.82 ± 22.97 and 2.14 ± 2.93 in groups 1 and 2, respectively (p < 0.001). The TCA was the only clinical factor associated with the rate of ECD change (regression coefficient, β = 1.254, p < 0.001). The tipping point in the TCA was 26.70° (95% confidence interval, CI: 23.75–29.64°). The mean TCD (mm) was 0.98 ± 0.38 and 1.26 ± 0.39 (p = 0.002), and the mean TCA (degrees) was 28.67 ± 7.79 and 36.35 ± 5.35 (p < 0.001) in groups 1 and 2, respectively. Conclusions: A wider TCA was protectively associated with the rate of ECD change, and the TCA was significantly narrower in patients with ECD damage. When inserting a tube into the anterior chamber, surgeons should therefore try to secure a wide TCA of about 30°. In patients with a narrow TCA after AGV implantation, increased attention should be directed toward whether ECD decreases continuously.

XEN Glaucoma Implant for the Management of Operated Uncontrolled Glaucoma: Results and Complications during a Long-Term Follow-Up

“…In cases of operated uncontrolled glaucoma, use of glaucoma drainage devices (GDD) is often an interesting option. Their effectiveness is comparable to trabeculectomy; however, they present a relatively high risk of complications such as anterior chamber shallowing, choroidal detachment, filtering bleb leakage, blood in the anterior chamber, chronic corneal endothelial loss, hypotony, and macular edema [ 5 , 6 ]. In addition, GDD procedures are time-consuming and require great operating skill, especially in cases of conjunctival fibrosis wherein previous surgeries force the use of scleral quadrants other than the superior ones.…”

Effect of Guided Ahmed Glaucoma Valve Implantation on Corneal Endothelial Cells: A 2-Year Comparative Study

“…The TCD and TCA are both considered important tube parameters, but the TCD is not a fully independent variable since it is affected by the TL and TCA. 9 In this study, the mean TLs in both groups were not signi cantly different; therefore, the in uence of TL on TCD could be excluded.…”

“…8 Recent studies on tube parameters found that a longer tube-cornea distance (TCD) and deeper tubecornea angle (TCA) induced less endothelial cell density (ECD) loss after AGV implantation in the anterior chamber (AC), emphasizing the importance of accurately positioning the tube. 9,10 However, to the best of our knowledge, no comparative studies have been conducted on the surgical methods that may be useful for tube positioning in the AC.…”

Effects of Miosis on Anterior Chamber Structure in Glaucoma Implant Surgery

“…In both studies, the greatest cell loss was evident in the supratemporal location, where the tube was located. In studies using AS imaging [ 10 , 11 , 12 ], a shorter distance and a narrower angle between the tube and corneal endothelium were both risk factors for corneal endothelial cell loss. These results suggest that it is preferable to place the tube distant from the cornea during insertion in the AC, thereby reducing corneal endothelial damage after glaucoma implant surgery.…”

“…Koo et al [ 10 ] and Tan et al [ 11 ] concluded that tubes positioned closer to the cornea led to increased damage to adjacent corneal endothelium. Lee et al reported that the angle between the tube and the cornea was narrower in eyes with significant corneal endothelial damage than in eyes without damage (28.67 ± 7.79° vs. 36.35 ± 5.35°, p < 0.001), and the distance between the tube and the cornea was shorter in eyes with corneal endothelial damage than in eyes without damage (0.98 ± 0.38 mm vs. 1.26 ± 0.39 mm, p = 0.002) [ 12 ]. They suggested that during its insertion into the AC, a considerable distance is required between the tube and the cornea to reduce corneal endothelial damage after glaucoma implant surgery [ 10 , 11 , 12 ].…”