Laser Peripheral Iridotomy (LPI)
What is laser peripheral iridotomy (LPI)?
A laser peripheral iridotomy (LPI) is a non-invasive treatment used to treat angle closure and reduce the risk of acute angle closure attacks (sudden spikes of very high intraocular pressure due to blockage of drainage channels). LPI uses a laser beam to create a small hole in your iris. This hole is not visible to the naked eye (Photo 1).
Why do I need this procedure?
In healthy eyes, the fluid in the eye (aqueous humour) flows through the pupil into the front of the eye and drains through drainage channels called the trabecular meshwork. However, in some patients these drainage channels are narrow and are obstructed by the iris (the
coloured part of your eye). This condition is called angle closure (Figure 1). As aqueous humour cannot leave the eye, eye pressure may increase which may lead to irreversible optic nerve damage (glaucoma) and vision loss. The objective of the LPI is to create a permanent alternative passage through which fluid can flow through and push the iris tissue backward, thus unblocking the drainage channels (Figure 1).
Two groups of patients with angle closure will benefit from LPI. Please tick accordingly:
The first group are those who have been diagnosed with an acute primary angle closure attack or primary angle closure glaucoma. If LPI is not performed early to reduce eye pressure, further irreversible optic nerve damage, vision loss and even blindness may result. LPI for these patients helps to relieve the obstruction of the drainage system and reduces the risk or stop progression of glaucoma. In some patients, glaucoma medication and/or surgery may be necessary in addition to LPI.
The second group of patients are those who have been diagnosed with angle closure without glaucoma but may have either normal (primary angle closure suspect) or raised eye pressure (primary angle closure). Compared to observation, LPI reduces the risk of progression to primary angle closure and acute primary angle closure by about 50% over 5 years.
Certain patients may be at higher risk of developing angle closure attack or glaucoma. Risk factors include patients with family history of acute angle closure or angle closure glaucoma, symptomatic patients complaining of unilateral headaches and/or eye pain as well as patients with retinal disease who will require regular dilated eye examinations.
These patients will be strongly encouraged to undergo LPI.
What are the preparations?
Allow half a day for the procedure which will be performed in the laser clinic. LPI is not surgery and hence no fasting or admission is required. Do not drive as your vision may be blurred for about a day after treatment. Come with a companion so that he/she can take you home safely.
Before the procedure, your vision will be measured and you will be given an eye drop (pilocarpine) before the laser is carried out. The pilocarpine drop often causes a transient headache, and may affect the vision, for example by altering the focus of the eye, and making things appear darker and more blurred than usual. These effects are normal and temporary.
How is the procedure performed? LPI is performed under topical anaesthesia (eye drops). These often cause a slight tingling or stinging for a few seconds. A contact lens will then be placed on the eye. The lens is used to improve the doctor’s view and prevent the eye from closing. It is important not to move during the procedure; the majority of patients manage to keep still without any problems.
Two different lasers are used during the procedure. The first laser is used to create a partial thickness hole in the iris. You will then be required to transfer to the second laser machine located in the same room. The second laser is used to punch through the iris, ensuring that an adequately sized and functioning iridotomy (“hole”) is made. A clicking sound may be heard during the laser treatment and most patients usually do not experience any discomfort apart from a flicking sensation during the LPI.
What are the risks and complications of the procedure?
Generally, LPI is a very low-risk procedure. The common side effects of LPI are a temporary rise in intraocular pressure and inflammation. If these conditions occur, they can be treated with intra-ocular pressure lowering and/or anti-inflammatory eye drops. Occasionally the LPI is incomplete, not big enough, or closes up. If this is the case, we will have to repeat the treatment at a later date.
In some patients, bleeding from the iridotomy (laser hole inside the eye) may occur and can cause blurring of vision and floaters. This usually settles within a few days. Other rarer complications of LPI include visual phenomena such as post-procedure double vision, glare, haloes, shadows and lines. These symptoms are often mild and usually disappear over time.
However, occasionally these visual disturbances may persist and occur under certain lighting conditions. Very rarely, the laser can damage the cornea, lens or retina.
What do I expect after the procedure?
Post procedure, you may be dazzled by the laser light and may have difficulty seeing for a short time. This usually improves after about 30 minutes. A nurse will be present to monitor you as well as measure your intra-ocular pressure 30 minutes after the laser treatment. You may go home after resting for about 1 hour. Aside from eye drops to apply at home for 1 week after the LPI, no special after-care is required. Medical leave can be given for the rest of the day if necessary and work can resume the next day. Do note that your vision may remain blurred for about a day due to mild inflammation in the eye. Your doctor may prescribe glaucoma medications following the procedure depending on your eye pressure or glaucoma condition.
Should you develop persistent sudden drop in vision, redness or pain in the eye, please return immediately.
What are the other options?
An alternative treatment for angle closure is surgery. This involves surgical lens extraction with intraocular lens insertion. Compared to LPI, surgery is a higher risk procedure. For this reason, lens extraction is usually only recommended for patients who are already developing visual problems from cataract.
Asymptomatic, low risk patients diagnosed with angle closure without glaucoma may opt not to undergo LPI, as studies have shown that the incidence of angle closure disease is very low (estimated to be 5 - 10% over 5 years). They will continue to be monitored 6- to 12-monthly for acute angle closure attack or development of glaucoma.
What will happen if I do not undergo the procedure?
Patients who have been assessed by their doctor to benefit (see above) from LPI but choose not to undergo the procedure are at risk of acute angle-closure attacks and/or deterioration of glaucoma. This can result in irreversible loss of vision from glaucoma which may lead to blindness.
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DISCLAIMER: This information sheet mentions some of the more common or important risks of surgery/ procedure. This list is NOT meant to be, and CANNOT be exhaustive.
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This brochure was developed together with NHG Eye Institute partners.
Yishun Health is a network of medical institutions and health facilities of the National Healthcare Group in the north of Singapore. It comprises Khoo Teck Puat Hospital, Yishun Community Hospital and community extensions such as Admiralty Medical Centre and Wellness Kampung. Khoo Teck Puat Hospital • (65) 6555 8000 • www.ktph.com.sg Yishun Community Hospital • (65) 6807 8800 • www.yishuncommunityhospital.com.sg