iStent Implantation


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WHY IS ISTENT IMPLANTATION NECESSARY?

The iStent is implanted at the same time as cataract surgery for patients who have both cataract and glaucoma. The aim of the iStent is to decrease the eye pressure so that you can reduce the number of pressure-lowering eye drops you use. In some cases, it may be possible for you to stop your pressure-lowering eye drops completely.

The lens is the middle window inside the eye that focuses light entering the eye. As you age, your lens becomes gradually more cloudy – this is called a cataract. As the cataract progresses, you may experience worsening vision and increasing glare. During cataract surgery, the cloudy lens inside your eye is removed and replaced with an artificial clear lens implant. The lens implant remains in the eye permanently.

(Image adapted from the internet)

Fluid in the eye (aqueous) is produced by the ciliary body, and drains out through the trabecular meshwork (drainage pathway) in the drainage angle. Sometimes the trabecular meshwork no longer copes, preventing aqueous from draining out easily. This causes pressure to build up in the eyeball. When the pressure in the eye is too high, it can cause optic nerve damage and permanent vision loss - this is called glaucoma.

(Image adapted from the internet)



WHAT DOES THE ISTENT DO?

The iStent is one of the glaucoma surgery techniques called minimally invasive glaucoma surgery (MIGS). In contrast to traditional glaucoma surgery, MIGS is quicker and easier to perform and has less risk of complications, but has reduced overall pressure control.

The iStent is one of the earliest MIGS techniques. It is very small, only measuring 0.4 mm long. Implantation of the iStent involves puncturing the stent through the trabecular meshwork. This effectively creates a ‘hole’ in the meshwork, thus allowing the aqueous to drain out of the eye in a controlled manner and reducing pressure.

(Image adapted from the internet)

There is no change to the way the cataract surgery is performed. Two iStents are implanted into the trabecular meshwork after the lens implant has been inserted into the eye. This adds around 5 minutes to the overall cataract surgery time.



WHAT ARE THE POTENTIAL RISKS?

IStent implantation is very safe. Apart from the usual risks associated with cataract surgery, additional risks specific to the iStent are rare. These include:

● Bleeding into the eye. This is generally mild and settles over a few days.
● IStent implantation issues, such as implantation at a non-ideal location,
   depth or angle. Rarely, the iStent may become dislodged from its
   implanted position. No harm or damage will be caused to the eye, so
   usually no additional procedure is needed to reposition or remove the iStent.
   However, you may need to restart your glaucoma eye drops.
● Failure to work. It is possible that the iStent may not work in your eye
   despite successful and uncomplicated implantation. Sometimes the iStent
   works well initially, but the pressure gradually increases over time. If this
   occurs, you may need to restart your glaucoma eye drops.
● Problems with the MRI may occur if you require an MRI scan at the
   higher 3 Tesla setting. There is no problem with the standard 1.5 Tesla
   MRI scan.

Medicare Australia only allows iStent implantation during cataract surgery. If your cataracts have already been removed, you will not be able to have iStents implanted.



WHAT SHOULD I EXPECT?

Cataract surgery with iStent implantation is a hospital-based day case procedure performed under local anesthetic. The operation is usually performed one eye at a time.

Before and during surgery:

All the instructions before and after surgery are the same as for cataract surgery. All the precautions and surgical steps taken are the same as for cataract surgery. The following are the extra steps that will occur during iStent implantation:

● You will be asked to rotate your head to one side. Please remain still
   during the procedure.
● A contact lens will be placed on your eye.
● The iStents will be implanted. You should not feel any pain during iStent
   implantation.

After surgery:

After cataract surgery and iStent implantation, a pad and shield will be placed over your eye. The pad and shield can be removed the next day, and you can start your normal postoperative eye drops, usually a steroid (Prednisolone or Dexamethasone) and an antibiotic (Chloramphenicol) 4 times daily for 3 to 4 weeks.

You will usually be reviewed the day after surgery to check the positioning of the iStents and your eye pressure. The reduction in the eye pressure with the iStent may not be immediate, so you may still have to continue your usual pressure-lowering eye drops for a few weeks.

Over the next few days, you may experience blurriness, discomfort, sensitivity to light, and blood around the eye. This will gradually improve with the eye drops. As with routine cataract surgery, it can take a week or two before you notice any improvement in your vision.

Please contact the clinic immediately if you experience pain or a sharp drop in vision.




Learn more about cataract surgery

Learn more about the techniques of cataract surgery

Learn more about the steps involved in cataract surgery

Learn more about what to expect with cataract surgery

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Return to: Vision & Eye Health



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