The original concept of the modern glaucoma drainage device (GDD) had an equatorial plate with 2 eyelets to securely suture it to the sclera.1 This anchoring has remained the standard of care for GDD implantation to prevent migration of the plate.
In recent years, some have developed techniques to obviate the need for plate fixation sutures and thereby enhance efficiency and avoid the minimal but serious risk of scleral perforation. The “hang back” technique has been proposed for implantation of the Ahmed FP-7 glaucoma valve (AGV), which involves suturing the tube to the sclera with the plate simply “hanging” from the tube.2 The orbital anatomy prevents anterior migration of the AGV plate when it is placed posteriorly to the equator.3 The inherent stability of the plate is verified by confirming the absence of movement of the plate with infraduction of the globe and by pulling the tube anteriorly. The tube is either sutured to the sclera or passed through a long intrascleral track to provide resistance against anterior migration of the tube further into the anterior chamber. Posterior migration of the plate, ie, the long scleral track itself, or a suture, holds the anterior portion of the tube in place.2-4
An Argument for Continued Use of Plate Fixation Sutures
Hamed Esfandiari, MD; Angelo P. Tanna, MD
There is insufficient longitudinal follow-up published in the peer-reviewed literature on sutureless AGV implantation to assess its efficacy and safety.3,5,6 Although 2 studies reported favorable outcomes with this technique,3,6 Singer et al found a high rate of plate migration.5 One concern is the possible increased risk for erosion of the GDD tube due to increased motion when the plate is not securely anchored to the sclera. Also, increased motion of the plate itself may alter the characteristics of the fibrotic response, possibly resulting in a thicker fibrotic capsule and higher late postoperative intraocular pressure (IOP).
Another safety concern with the sutureless technique not addressed with these studies is the position of the posterior edge of the plate in relation to the optic nerve. Because the “hang back” approach largely relies on implantation of the plate farther posteriorly than the often-used 8 mm landmark, there is a concern that optic nerve compression could occur.7 Careful measurement of the distance between the plate and the limbus is needed to avoid impinging on 2 mm “safe zone” around the optic nerve to mitigate the risk of causing a compressive optic neuropathy. This is of particular concern with the FP-7 AGV because of its long 16 mm anterior-posterior dimension. For example, an eye with an axial length of 22 mm and a horizontal white-to-white distance of 11.7 mm requires positioning the anterior edge of the Ahmed FP-7 plate no more than 8.0 mm from the limbus to avoid encroachment on the 2 mm safe zone.8,9 None of the studies evaluating GDD implantation without suture fixation of the plate evaluated optic nerve structural or visual field tests to assess the safety of this procedure.
Efficiency and innovation are important, but we believe that the outcomes of glaucoma tube shunt surgery are more predictable if the GDD plate “hangs tight” to the sclera with a nonabsorbable suture rather than “hanging back” in the retrobulbar space. Trimming the posterior edge of the plate or suturing the plate closer to the limbus is recommended in smaller eyes or when the GDD is implanted in the superior-nasal or inferior-nasal quadrants.
Tube Shunts May Not Require Plate Sutures
Jonathan S. Myers, MD
Tube shunt plate fixation sutures have been standard teaching since the first shunts were placed. The role of sutures in holding the shunt in place until the capsule develops around the plate seems obvious. Nonetheless, these sutures may be omitted with some modification of the standard tube shunt surgical technique.
Every glaucoma surgeon has seen that when the tube shunt plate slips far enough behind the equator, its tendency is to move further back, not forward. Thus, placing the plate behind the equator is sufficient to prevent anterior migration prior to capsule formation, after which the plate is generally fixated for the long term. This technique requires secure fixation of the tube to prevent the tube from sliding forward or back prior to capsule formation.
Why skip sutures? Beyond convenience, shorter surgeries with less manipulation and retraction generally lead to less postoperative pain and swelling and a quicker recovery. There also is a risk of scleral perforation with sutures, especially for surgeons with less experience. There are other factors that may make this approach appealing: poor exposure, small interpalpebral fissures and tight orbits, thin sclera, a high buckle, or patients who cannot hold still or whose medical condition puts an emphasis on quicker surgery.
I’ve realized that the less I do, the less I do wrong. In surgery, the fewer steps there are, the more precisely each step needs to be done. Although several authors have shown that tube shunt surgery without plate sutures can be as safe and effective as with sutures,3,5,10,11 others have had plate migration issues.6,12 Singer et al collectively reported on 266 eyes with a total of 2 cases of anterior migration.6 Kapelushnik et al reported high rates of migration on overlapping groups of eyes, even when Vicryl sutures were used in a concurrently reported cohort.12 There are clearly surgeon and patient factors that have led to these disparate outcomes. Shallow orbits and very large globes may be more at risk for migration, whereas in other cases the benefits of the sutureless approach may outweigh the perceived risks.
Surgical technique evolves over time. Few surgeons do retrobulbar injections for cataract surgery anymore, although retrobulbar blocks arguably resulted in very still and comfortable eyes, with very rare complications. For some cases and surgeons, retrobulbar anesthesia may be the preferred approach. For many surgeons and patients who have made the required adaptations, newer techniques are preferable. GP
References
- Molteno AC. New implant for drainage in glaucoma. Animal trial. Br J Ophthalmol. 1969;53(3):161-168. doi:10.1136/bjo.53.3.161
- Pandav S, Banger A, Ichpujani P, et al. Results of Ahmed glaucoma valve implantation with “hangback” technique. Presented at: World Glaucoma Congress; Paris; 2011.
- Pham CN, Radcliffe NM, Vu DM. Surgical outcomes associated with a sutureless drainage valve implantation procedure in patients with refractory glaucoma. Clin Ophthalmol. 2018;12:2607-2615. doi:10.2147/OPTH.S186369
- Radcliffe, NM. Sutureless Ahmed valve by Dr. Radcliffe. 2017. https://www.youtube.com/watch?v=rTr5QhBZMMc .
- Sanvicente CT, Moster MR, Lee D, et al. A novel surgical technique for Ahmed Glaucoma Valve implantation without plate sutures. J Glaucoma. 2020;29(3):161-167. doi:10.1097/IJG.0000000000001428
- Singer R, Kapelushnik N, Rotenstreich Y, Leshno A, Barkana Y, Skaat A. Surgical outcomes of Ahmed glaucoma valve implantation with plate fixation using vicryl sutures or no plate fixation. Eur J Ophthalmol. 2021;11206721211012869. doi:10.1177/11206721211012869
- Kahook MY, Noecker RJ, Pantcheva MB, Schuman JS. Location of glaucoma drainage devices relative to the optic nerve. Br J Ophthalmol. 2006;90(8):1010-1013. doi:10.1136/bjo.2006.091272
- The Freedman Margeta GDD Calculator. https://people.duke.edu/~freed003/GDDCalculator/
- Chandramouli SA, Glaser TS, Umunakwe O, et al. Glaucoma drainage devices calculator app: a modern clinical decision tool. Ophthalmol Glaucoma. 2021;4(5):550-551. doi:10.1016/j.ogla.2021.01.002
- Kahook MY, Noecker RJ. Fibrin glue-assisted glaucoma drainage device surgery. Br J Ophthalmol. 2006;90(12):1486-1489.
- Lee HM, Park KS, Jeon YY, et al. Clinical outcomes of Ahmed glaucoma valve implantation without fixation of a plate: the free plate technique. PLoS One. 2020;15(11):e0241886. Published 2020 Nov 6. doi:10.1371/journal.pone.0241886
- Kapelushnik N, Singer R, Barkana Y, et al. Surgical outcomes of Ahmed glaucoma valve implantation without plate sutures: a 10-year retrospective study. J Glaucoma. 2021;30(6):502-507. doi:10.1097/IJG.0000000000001813