Introduction
There are a number of laser procedures which are used to treat glaucoma, and similar to the page on surgeries, on this page we will describe only the most common ones which are likely to be used to treat your condition.
At this stage we would also like to mention LASIK procedures. LASIK is not a treatment for glaucoma but many of our patients have either already had LASIK, or are considering LASIK in the future. If you are considering LASIK in the future, and you have glaucoma already, please consult your ophthalmologist first, since some LASIK procedures require a temporary spike in the pressure inside the eyeball, and may worsen your condition. If you have already had LASIK in the past, it is essential that you tell your ophthalmologist, since the thickness of your cornea will now be significantly thinner than a normal cornea, and this will affect the accuracy of readings taken to establish your eye pressure. Alternate methods exist to measure your eye pressure, but the medical staff need to be informed that you have had LASIK in the past.
Here are the some of the most common laser procedures which your ophthalmologist may use to treat your glaucoma.
Laser peripheral iridotomy (LPI)
Laser peripheral iridotomy (LPI) is performed in patients with narrow drainage angles. The drainage angle refers to the angle between the cornea (the clear window at the front of the eye) and the iris (the brown/blue part of the eye).
When an eye specialist examines you on a slit lamp they may notice that the angle is narrow and recommend LPI. If LPI is not performed the patient is at risk if the eye pressure suddenly becoming very high.
This is because the drainage angle, already noted to be narrow, closes completely and so the internal eye fluid (or ‘aqueous’) cannot leave the eye in the usual manner and the eye pressure increases. This is what we refer to as ‘acute angle closure’ (see the page on What Is Glaucoma?) which can result in damage to the optic nerve and therefore loss of sight and/or glaucoma (specifically PACG).
LPI involves the creation of a tiny hole in the periphery of the iris which then acts like a safety valve for the eye pressure, such that the occurrence of acute primary angle closure (or sudden pressure rise) is much less likely. The LPI in itself does not eliminate the risk of developing glaucoma however, but it does reduce the risk.
Sometimes the patient already has developed glaucoma when the narrow angles are observed – in these cases LPI is still usually recommended although the glaucoma cannot be reversed. If a patient has some cataract, sometimes the specialist will advise performing cataract surgery rather than LPI.
This is because both procedures result in a much reduced risk of acute angle closure and if there is a cataract then performing the surgery will also improve the patient’s vision. LPI by itself does not result in improved vision.
What are narrow drainage angles?
You may have narrow drainage angles because the outer edge of your iris (the coloured part of the eye) is closer to the cornea (clear window at the front of the eye), causing the “drain” to be narrowed, and eventually blocking off the drainage of fluid from the eye. When this happens, the eye pressure increases dramatically. This may cause significant pain, blurring of vision and headache with nausea and vomiting. This is known as acute angle-closure. This is a serious condition and it can lead to permanent loss of sight.
An acute angle-closure attack is a medical emergency, and requires prompt treatment. Your ophthalmologist may recommend an emergency laser peripheral iridotomy, although if the pressure is too high, they may also recommend medication to lower your eye pressure to a safe level before doing the LPI.
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- Peripheral Iridotomy Post-laser
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- LPI before (A) & after (B)
What is a laser peripheral iridotomy (LPI)?
LPI is done in an outpatient setting in the laser clinic. In this procedure, a tiny hole is created at the periphery of your iris. This forms a permanent passage through which aqueous humour can flow through and pushes the iris tissue backward, thus widening the drainage channels. This will then reduce the risk of acute angle-closure.
Prior to the laser, the nurse will instill a miotic (an eye drop to make your pupil smaller). After instilling the anaesthetic eye drops, the ophthalmologist will put a special contact lens in your eye before applying the laser beam.
The treatment is painless due to the anaesthetic drop used to numb your eye before the laser, but you might experience a slight discomfort when the laser is being applied. This takes about 10 to 15 minutes.
After the procedure, you will return to the waiting area. Before you leave the eye centre, your ophthalmologist or nurse will check the eye pressure about half an hour later.
What are the benefits?
This procedure is performed to save your remaining sight. It will not restore any sight you may have already lost; neither will it improve your sight.
The laser treatment is to prevent a sudden (acute) rise in pressure within your eye. Without this treatment, you are at risk of developing sudden acute glaucoma and irreversible blindness.
Are there any risks?
Complications after this treatment are uncommon, but may include:
High eye pressure
Occasionally your eye pressure will rise immediately after laser treatment so it is important to check the eye pressure half an hour after the laser. If this happens, you may need extra treatment before you can go home. This treatment usually comes in the form of eye drops, but may also include tablets. Your ophthalmologist will discuss which treatment is suitable for you and advise on the treatment duration.
Closure of iridotomy
Rarely the laser beam opening is incomplete, or not big enough. This will be detected after your treatment, or on your follow-up visit. If required, the laser treatment will be repeated at a later date.
Glare, haloes and visual disturbances
Some patients may find the extra light entering through the new opening a little distracting, while others may experience visualising a “line” at the bottom of their field of vision at certain position of gaze. However, most patients find these visual disturbances tolerable.
Bleeding
There may be slight bleeding after the procedure and this can be treated with more frequent application of steroid eye drops.
Damage to the cornea
This is a rare but potentially sight-threatening complication. The cornea may lose its clarity and a corneal transplant may be necessary in the future.
Are there any alternatives?
An alternative to laser treatment is a cataract operation, which is not suitable for everyone. It also carries a greater risk of potential complications. There are no other alternatives to open up the drainage channels in your eye. Some patients with this condition also develop a persistent rise in their eye pressure. In this case, you may need eye drops or other treatments in the long term to keep your eye pressure within safe limits.
Please consult your surgeon if you have any further queries about the surgery.
Selective Laser Trabeculoplasty (SLT)
SLT is an office procedure which is delivered through the slit lamp. It is indicated for patients who have open angle glaucoma (or sometimes other types of glaucoma) and require additional eye pressure lowering.
The procedure delivers laser energy through a special contact lens to the drainage system of the eye. The mechanism of eye pressure lowering has been hypothesized to be due to biochemical changes at the trabecular meshwork. On average, SLT is able to reduce the IOP by around 20% but the effect tends to diminish with time. In about 20-30% of cases the SLT is not effective in lowering the eye pressure.
SLT is a safe procedure with little side effects such as a transient rise in eye pressure or inflammation but this can be successfully treated with a short course of eye drops.
Transcleral cyclophotocoagulation (TCP)
This laser treatment involves placing a probe placed on the surface of the eye to target the area called ciliary body. The ciliary body is the area of the eye that produces the internal eye fluid (called the “aqueous”). The procedure does not involve any cutting of the eye but typically a local anaesthetic injection is given below the eye to numb it. For this reason the procedure is carried out in the operating theatre.
The laser delivered through the probe to the eye causes an increase in the temperature of the ciliary body, essentially destroying that area and thereby decreasing the production of the aqueous fluid, resulting in a decrease in the eye pressure.
It can be quite effective but may result to other unwanted eye problems such as blurring of vision, thinning of the coat (sclera) of the eye, very low eye pressure (known as “hypotony”), eyeball size becoming smaller (known as “phthisis bulbi”), swelling of the back of the eye (macular oedema) or rarely, bleeding.
Because of the mentioned complications, this procedure is often used as last option for painful, poorly sighted or blind eyes, but can also be used in less severe cases.
Micropulse Trans-Scleral Cyclophototherapy (MPTCP)
This relatively newer treatment modality is regarded as a gentler version of TCP. The energy delivered to the eye is separated into short bursts to reduce energy/temperature build up. Just like for TCP, usually it involves giving a local anaesthetic injection under the eye and is performed in operating theatre.
Similar to TCP, MPTCP consists of a laser probe which rests and slides on the surface of the eye during the procedure which lasts for approximately 5 – 10 minutes. The mode of action is hypothesized to increase outflow of fluid inside the eye to reduce intraocular pressure.
After MPTCP, a patient is typically asked to instil anti-inflammation eye drops for up to 2 weeks. Relative to TCP, one of the key features of MPTCP is its good safety profile and there are minimal complications.