Trabecular micro-bypass shunt (iStent®): basic science, clinical, and future)

Area of Science:

• Ophthalmology
• Glaucoma Surgery
• Medical Devices

Background:

• Trabecular bypass stents (iSTB) present a novel alternative to traditional filtration surgeries for managing open-angle glaucoma.
• Specific patient populations, including those with prior ocular surgeries, high myopia, or on anticoagulants, may benefit from this less invasive approach.
• The iSTB offers a potential solution for rapid visual recovery in young patients, especially those with monocular vision.

Purpose of the Study:

• To evaluate the efficacy and safety of the micro-invasive trabecular bypass stent (iSTB) as an alternative surgical intervention for open-angle glaucoma.
• To identify ideal patient candidates and surgical considerations for iSTB implantation.
• To assess the potential of iSTB combined with medications in achieving target intraocular pressure (IOP).

Main Methods:

• The study discusses the implantation technique, emphasizing its precision and similarity to clear corneal cataract surgery and goniotomy.
• Patient selection criteria are highlighted, advising against those with congested episcleral veins or very high IOPs (>35 mmHg), and favoring patients with open angles and visible aqueous veins.
• The procedure involves placing trabecular bypass devices into the canal of Schlemm, requiring downstream patency of the collector channel system.

Main Results:

• Encouraging results show an average IOP of 11.8 mmHg after implantation of two iSTB stents and daily travoprost medication.
• These IOP levels are comparable to or better than those achieved with more invasive incisional surgeries like trabeculectomy.
• Long-term safety data are favorable, with IOP success dependent on the patency of the patient's outflow system.

Conclusions:

• Micro-invasive trabecular bypass stents are a viable surgical option for select open-angle glaucoma patients.
• Combining iSTB with medications can achieve significant IOP reduction, comparable to more invasive surgeries.
• Optimal outcomes depend on precise stent placement within the canal of Schlemm and the condition of the downstream outflow pathway.