Mr Raj can offer one of the most modern and sophisticated glaucoma surgery called iStents to his glaucoma patients. iStent surgery is a relatively new procedure that involves inserting a tiny hollow metal tube (stent) into the eye using minimally invasive microsurgical technique to help fluid to drain from the front chamber of the eye and help reduce pressure inside the eye.

 Dimension of the iStent:

• Length: 1mm (1/5th of the size of a grain of rice!)
• Height 0.33mm
• Weight: 60 Microgram
• Snorkel: 0.25mm x 120 Micrometer (bore diameter)

The iStent is a tiny titanium device, which resembles a bent pipe or periscope, is approved to treat moderate to advanced open-angle glaucoma in people who are already using medication to reduce high pressure in the eye. The iStent is a micro-bypass device which is inserted into the trabecular meshwork in order to re-establish the natural physiological flow of aqueous humour from the anterior chamber into Schlemm’s Canal in patients with primary open angle glaucoma (POAG). Trabecular micro-bypass surgery addresses a previously unmet need in patients with PAOG. It is the first procedure/device developed that is appropriate to treat mild-moderate and some advanced glaucoma patients. Whether performed as a standalone procedure or combined with cataract surgery, trabecular micro-bypass surgery results in a level of efficacy comparable to that of first-line glaucoma medications. Trabecular micro-bypass surgery avoids compliance issues and side-effects of eye medication at a low level risk no greater than that of cataract surgery alone.

Other Alternatives

Eye drops, Tablets, Selective Laser Trabeculoplasty, Cyclodiode Laser Treatment and Glaucoma Drainage Surgeries including Glaucoma Tube implants.

What are the risks of not having the procedure?

If the eye pressure remains elevated despite medical therapy/laser treatment then there is a risk that your glaucoma may progress and your vision and visual field will deteriorate and may lead to permanent blindness.

What the procedure involves

This operation is performed as a day case procedure and under local anaesthetic injection. Trabecular stent bypass microsurgery is less surgically demanding than conventional penetrating glaucoma surgery. It aims to create a bypass channel to allow for equalisation of pressure between the anterior ocular chamber and Schlemm’s canal. The procedure is often combined with phacoemulsification and intraocular lens insertion for the concomitant treatment of cataracts, although it can also be used alone without cataract surgery. With the patient under local anaesthesia, a small corneal incision is made and the angle is opened using viscoelastic injected into the anterior chamber. Under gonioscopic guidance (a lens with a mirror or prisms used to view the iridocorneal angle), a small L-shaped metal stent is slid through the trabecular meshwork (a small slit may be necessary) and into Schlemm’s canal using a special applicator device. The position of the stent is verified, the viscoelastic is removed, and the applicator withdrawn. More than one stent may be inserted during the same procedure.

Managing Your Glaucoma With an iStent

The iStent is a highly innovative titanium stent which is implanted through the trabecular meshwork and placed into the eye’s drainage channel (Schlemm’s Canal). The iStent channels aqueous humour via a tiny lumen through the trabecular meshwork directly into Schlemm’s Canal re-establishing natural, physiological outflow. Overtime this canal can collapse and the iStent can re-open this space, a little like a heart stent.

The iStent is an “L-shaped device” measuring only 1 mm in length and it is currently the smallest device implanted in a human body. Once the stent is in place it can then lower and control the pressure within the eye. Mr Raj and his team will be able to advise you on your suitability for this procedure and any further information you require.

Safety of the iStent

The iStent has been approved by the US FDA (United States Food and Drug Administration). There have been no long term significant or persistent side effects. The iStent is made from non-magnetic titanium, the same material used for replacing heart valves so it won’t be rejected by the body, neither does it cause an allergic reaction. It will not set off airport scanners and will not cause any problems if you need to have an MRI scan.

 THE SURGERY

iStent® implantation is usually performed under local anaesthesia as the procedure is relatively short taking about 30 minutes. When combined with cataract surgery the procedure will usually take approximately 50-60 minutes.  

What Can I Expect After SURGERY

The iStent should start working immediately after surgery or at least within the next few weeks and Mr Raj will then look at the possibility of reducing your medication. You will be having an eye shield for the 1^st day/night which you can remove the following morning. You will be given an eye drop to use, usually 4 times a day to the operated eye for 4 weeks and Mr Raj will arrange to see you in his clinic later. In a high percentage of cases, you will be glaucoma medication free after the procedure or at least using fewer drops or your eye pressure will be controlled with eye drops if it was not the case before. In a US study 73% of the patients remained medication free after 12 months. In a published study, 240 eyes received the iStent, and a year later 68 percent had the study target pressure of 21mm of mercury or lower without the use of medication to lower eye pressure, compared with 50 percent who had cataract surgery alone. But the results are usually individualized based on your own circumstances.

CONTRAINDICATIONS

The iStent® Trabecular Micro-Bypass Stent is contraindicated under the following circumstances or conditions:

• In patients with angle closure glaucoma and certain other secondary glaucoma.

• In patients with retrobulbar tumor, chronic inflammatory disease, thyroid eye disease, Sturge-Weber Syndrome or any other conditions where the trabecular meshwork, Schlemm’s Canal or collector channels are compromised.

What are the benefits of iStent?

The benefit of iStent is that it may prevent your glaucoma from getting worse by lowering your eye pressure. Results from one hospital show that on average the iStent reduces eye pressure by 30%, however each patient is different and the exact eye pressure result varies. The iStent can also reduce your use of eye drops for glaucoma. 7-8 out of 10 patients have been able to stop their glaucoma drops completely following this procedure. Other benefits of iStents are: a less invasive surgery as compared to complex and long drainage surgeries and faster recovery time. It provides an extra option for controlling glaucoma where glaucoma medications, laser or other complex glaucoma surgeries are not appropriate.

However, iStent will not cure your glaucoma, reverse any damage already caused by glaucoma or bring back any lost vision.

Potential Risks & Potential Complications

Although iStent has been approved for use, it is a new procedure so there is still a lot to learn about it and some of the safety issues may not be known. Data is continually being examined on the outcomes for patients who have the implant, so that we can understand more about it.The most common post-operative adverse events reported in the randomized pivotal trial included early post-operative corneal edema (8%), BCVA loss of ≥ 1 line at or after the 3 month visit (7%), posterior capsular opacification (6%), stent obstruction (4%) early post-operative anterior chamber cells (3%), and early post-operative corneal abrasion (3%). 

There could also be risk of obstruction & dislocation. It may not be sufficient to provide long term glaucoma control and there may be failure & or loss of effect with time (as this is a relatively new procedure, long term data is not available).It also carries the risk of an intraocular surgery like risk of reduced or loss of vision, pain, bleeding & infection, ocular inflammation and there may be need for further procedures or treatment.

iStent :Further information: 

www.glaukos.com/istent

http://www.glaukos.com/patients/istent-overview

iStent Video: http://www.youtube.com/watch?v=4nzJAgn4z2k

If you have any of the following after an iStent surgery:

• Sudden loss of vision
• Severe and unrelenting pain
• Abnormal discharges from the eye

Please contact your local eye emergency service.