Microinvasive glaucoma surgery (MIGS) has revolutionized the treatment of glaucoma. With compliance concerns regarding topical medications, the benefits of MIGS may even outweigh those of medical therapies in patients with pressures adequately controlled on medications.
Several companies are currently striving to add more tools to the MIGS armamentarium (including Glaukos with the iStent Trabecular Micro-Bypass device).
Past focus for stents has been in the trabecular meshwork. However, companies are currently developing suprachoroidal devices, which are in various stages of FDA review. These include the iStent SUPRA (Glaukos), the CyPass Micro-Stent (Alcon Laboratories), and the Solx Gold Shunt (Solx). These additions will provide more surgical options and allow surgeons to individualize treatments to patients more effectively.
Trabecular bypass stents
The eye has two outflow pathways: the trabecular outflow and the uveoscleral outflow pathway. The trabecular outflow pathway is more pressure dependent and is where 75% of the aqueous humor outflow occurs,1 making this area a logical place to insert a stent to restore natural physiologic aqueous outflow.
The episcleral venous pressure present is in the range of 6 to 12 mm Hg, and while distal outflow resistance adds a few mm Hg to the IOP,2 trabecular bypass stents are still capable of producing effective IOP lowering. The essential benefit of the episcleral venous pressure is that it virtually ensures no hypotony will occur.
The iStent has a strong safety and efficacy profile, as proven in the pivotal FDA trial.3 Results have only improved with time as surgeons continually become more experienced with the procedure.