iStent is a Safe & Effective Treatment for Glaucoma
The iStent is the first ab interno (from the inside) micro-bypass implant for the treatment of glaucoma. The iStent is made of titanium and is a tube-like device only 1 mm in length with a microscopic opening of only 120 microns in diameter. It is believed to be the smallest medical device ever implanted into the human body.
The iStent is meant for use with patients that require cataract surgery. The device is implanted during cataract surgery after the artificial lens implant IOL is placed within the eye.
The iStent has been approved in Canada and Europe for many years. However, it did not receive FDA approval until June 25, 2012.
How the iStent Works
High intraocular pressure ”IOP” (fluid within the eye) is the only controllable factor when treating glaucoma and is the number one risk factor for glaucoma. The main cause of elevated eye pressure in patients with primary open-angle glaucoma is a reduction of the aqueous outflow in an area called the trabecular meshwork. Up to 75% of resistance to outflow is located in the trabecular meshwork.1
The iStent allows the aqueous fluid to bypass the trabecular meshwork and flow into Schlemm’s canal, which allows the aqueous fluid to leave the eye so that when new aqueous is produced within the eye there will not be such a pressure elevation. The iStent increases aqueous outflow through its normal pathway through Schlemm’s Canal. 2,3
Research Proves the Effectiveness of the iStent
iStent Results Show Effective Reduction of Intraocular Pressure. Many studies have been performed on the iStent. A multicenter study in Germany, Switzerland and Spain revealed an intraocular pressure reduction that ranged from 3.4 to 5.9 mm Hg when combined with cataract surgery. One year after the surgery patients were still able to eliminate 1 to 1.3 glaucoma medicines from their previous eye drop treatment plan.
It is worth noting that modern day cataract surgery alone is capable of slightly reducing IOP. However, the longevity and effect on the diurnal (variation of IOP during the day) pressure is unknown for cataract surgery alone.
Researchers in Italy compared cataract surgery alone vs. the iStent with cataract surgery5.
15 months post-operative
Cataract Surgery Only
Baseline IOP 17.3
iStent with Cataract Surgery
Baseline IOP 17.9
IOP - 15.7
After discontinuing all eye medicine for one month, the IOP was 19.2
IOP - 14.8
After discontinuing all eye medicine for one month, the IOP was 16.6
24% of patients in the Cataract Surgery Only group were able to discontinue glaucoma eye drop medicine.
67% in the iStent group were able to discontinue glaucoma eye drop medicine
Researchers in Canada proved similar results4:
In 61 patients, two or three iStents were implanted instead of only one iStent and the IOP average was 13.9 mm Hg. Three iStents showed very good control and 93% of all patients were able to discontinue glaucoma eye drop medicines.
All of these investigators agree on the safety of the iStent. There were no adverse complications that are commonly encountered when trabeculectomy is combined with cataract surgery. Caution is urged in patients with narrow anterior chamber angles and plateau iris configuration.
Good Candidates for the iStent
The iStent is indicated for implantation in patients with mild to moderate primary open angle glaucoma that also need cataract surgery. It is suitable for patients whose intraocular pressure is either uncontrolled or borderline controlled by current glaucoma medicines; or patients (or their doctor) that want to reduce or eliminate glaucoma eye drop medicines.
Patients with narrow anterior chamber angles or those with severe glaucoma are not appropriate candidates for the iStent. However, patients with pseudoexfoliation or pigment dispersion syndrome usually have very good outcomes.
iStent is Recommended
Current research shows good IOP control with the iStent along with a good safety profile. Patients are comfortable and recover quickly from the procedure. The iStent procedure does not affect the patient from undergoing more aggressive glaucoma surgery at a later date. All results to date show the iStent will be a very positive treatment option for glaucoma patients that also have cataracts when approved by the FDA.