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Micro-stents promising, but more data needed
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An ideal glaucoma surgery should be safe and effective, with a good IOP-lowering effect over time. The cost of adjuncts and consumables should be reasonable, and the surgical procedures should be brief and easy to learn.
At present, patients who are intolerant of IOP-lowering medications are treated mostly with conventional surgery such as trabeculectomy, which is rather “invasive” and usually traumatic, posing considerable risks to advanced glaucoma patients. In the worst-case scenario, the patient may lose the last bit of the central island of vision he or she had and become totally blind. New minimally invasive surgical procedures and methods are needed to further enhance the safety and the efficacy of glaucoma surgery, particularly for those with advanced glaucoma.
Micro-stents are one of the major focuses of glaucoma management in recent years. They can lower the IOP of early to mild glaucoma patients, although the IOP-lowering effect is less significant than conventional surgery. Micro-stents are generally believed to be a safer, efficient, less-invasive and tissue-sparing procedure with minimal trauma and good efficacy in terms of IOP lowering. After years of evolution, the latest micro-stents may be able to treat advanced glaucoma by directing aqueous outflow externally to the sub-Tenon’s or subconjunctival space.
There are different stents available, most of which have already obtained the CE mark. Some of them are in clinical trials before their launch on the market. The first-generation iStent (Glaukos) is approved by the U.S. Food and Drug Administration and has the CE mark, and patients were followed up for at least 5 years. Next-generation products such as CyPass (Transcend Medical), Hydrus (Ivantis), Xen (AqueSys) and InnFocus (InnFocus) can be used to treat patients with different stages of glaucoma.
One of the challenges that all micro-stents, as well as glaucoma surgery in general, face is the maintenance of the IOP-lowering effect over a reasonable long period of time. Take the first-generation iStent as an example. Increasingly more patients had to turn back to medications as time went by. The rate of success dropped from 83% in the first year after surgery to 25% 5 years after surgery. Although half of the patients had a reasonable off-medication period for 3 to 4 years, more stable and simpler treatment procedures with a long-lasting IOP-lowering effect are often sought by both the surgeon and the patient. Simpler surgical procedures would encourage the surgeon to operate early, lowering the potential of developing complications.
Micro-stents may be an option among various glaucoma treatments. Nevertheless, a majority of these IOP-lowering devices lack large-scale multicenter landmark clinical trials to prove their safety and long-term efficacy. Given the fact that the failure rate tends to increase with time, further studies are also warranted to identify the risk factors and patients who are most suitable for micro-stent implantation. After all, both surgeons and patients are data-driven. More evidence is needed for micro-stents to have an established role in the management of glaucoma.
For more information:
Dennis S.C. Lam, MD, FRCOphth, can be reached at State Key Laboratory in Ophthalmology, Sun Yat-Yen University, 54 South Xianlie Road, Guangzhou 510060, People’s Republic of China; +852-3997-3266; fax +852-3996-8212; email: dennislam.gm@gmail.com.
Disclosure: Prof. Lam has no relevant financial disclosures.