There’s a new device available to help in the surgical management of patients with glaucoma: the Glaukos iStent. After implanting a pair of these in each of three patients, here are my initial thoughts along with links to some recent publications. I have also included a video of the second patient in whom I used these implants and several recent references on the device. The iStent was approved in Canada in April 2010 but still awaits FDA approval in the United States.
The ideal patient for this device is a patient who is scheduled for cataract surgery in whom their glaucoma is not under ideal control. For example, if a patient requires three glaucoma medications already to keep their glaucoma under control or is not quite controlled on medical therapy. This device has a very good chance of drastically reducing a patient’s dependency on glaucoma medications to achieve intraocular pressure (IOP) control when performed at the time of cataract surgery. I would still be inclined to recommend a trabeculectomy without cataract surgery as a primary procedure in a patient, even if they have a cataract present, if their glaucoma is not ideally controlled on current medical therapy.
In order to perform this type of surgery, the ophthalmologist needs to be VERY comfortable with performing gonioscopy to clearly see the trabecular meshwork. The view in the video is an accurate depiction of what I was seeing when performing the surgery. You will notice when the second stent is being placed that the act of inserting the device was enough to obscure the view. There is no point in even opening the packaging for the iStent if the angle is not CLEARLY visualized. As when using a Sussman or Zeiss-type goniolens in the office setting, it is easy to distort the cornea if you press too hard with the operative goniolens, rendering the view too blurry. If you are an ophthalmologist and are considering performing this surgery, make sure you are very proficient with gonioscopy in the office with an indentation lens such as the Sussman or Zeiss.
There will be bleeding as the blood contained in Schlemm’s canal makes its appearance upon iStent insertion. If the stent does not go in without resistance and does not cause a small amount of bleeding, then you are probably in the wrong plain. The video clip above was of the second case I performed. On my first case, the tip of the stent touched the trabecular meshwork when I was introducing the device into the area of the angle which resulted in instant bleeding and obscuration of the meshwork. I was able to inject additional viscoelastic material which pushed the blood out of the way to allow proper visualization. It is important that before impaling the angle that you touch it with the flat edge of the stent or its angled corner near the insertion probe, bother of which are not sharp, in order to gain your perspective on where the angle is located. Due to the optics of the system, objects may be closer than they appear and at a slightly different orientation. You ultimately enter the meshwork with the stent at what looks like 1/3 of the way down from the top of the angle which actually ends up being the middle of the trabecular meshwork.
At the one week mark on the three patients, two patients have pressures in the mid-teens and are not on any glaucoma medications. The patient who had bled on initial introduction of the stent into the eye and was on 4 glaucoma medications prior to the surgery, required one of their glaucoma drops to be resumed in order to regain better IOP control. I will update this article in the weeks ahead with more details of the post-operative course of the eye pressures.