GLAUCOMA LASER TREATMENT

If glaucoma is not controlled with the help of medicines, if the side effects of the medicines are not well tolerated and the patient is non-compliant, or cannot afford the cost of the medicines, the second option is LASER TREATMENT. There are various types of lasers that are used in the treatment of glaucoma.

YAG Laser Peripheral Iridotomy

In ‘Angle Closure Glaucoma’, the most common treatment used is laser. The laser (YAG Laser) is used to create small holes (Peripheral Iridotomy) in iris (the part of the eye which gives it the colour). The holes form alternate channels for flow of aqueous fluid and prevents closure of the angle and the drainage of the eye.  A small opening is made in the iris so that the stagnant fluid finds a way to the anterior chamber, the front portion of the eye, and subsequently drained off. This is an OPD procedure, done under local anaesthetic drops and takes only a few minutes to be completed. After the laser, you can wash your eye with water and can lead a normal life.

Laser peripheral iridotomy (LPI) is the preferred procedure for treating angle-closure glaucoma caused by relative or absolute pupillary block. LPI eliminates pupillary block by allowing the aqueous to pass directly from the posterior chamber into the anterior chamber, bypassing the pupil. LPI can be performed with an argon laser, with a neodymium: yttrium-aluminium-garnet (Nd:YAG) laser, or, in certain circumstances, with both.

Indications

Indications for LPI include the following:

• Acute angle-closure glaucoma
• Chronic angle-closure glaucoma
• Fellow eye of acute angle-closure glaucoma
• Narrow/occludable angle
• Miscellaneous conditions, including phacomorphic glaucoma, aqueous misdirection, nanophthalmos, pigmentary dispersion syndrome, and plateau iris syndrome

In patients with acute angle-closure glaucoma, LPI should be performed after intraocular pressure (IOP) and intraocular inflammation are controlled. The aim is to prevent another attack of acute angle-closure glaucoma or progression to chronic angle-closure glaucoma. In patients with chronic angle-closure glaucoma, IOP may remain the same or be lowered after LPI, depending on the extent of peripheral anterior synechiae.

The fellow eye in a patient with acute angle-closure glaucoma or chronic angle-closure glaucoma has a 50% chance of developing acute angle-closure glaucoma. Therefore, if an occludable angle is noted on examination, LPI should be performed.

Certain patients, especially hyperopic patients, are at increased risk of having narrow angles. Therefore, gonioscopy should be performed. If narrow/occludable angle is noted on the examination, LPI is recommended.

Contraindications

Contraindications for LPI include conditions that cause poor visualization of the iris, angle closure due to synechial closure of the anterior chamber angle, and a patient who is unable to cooperate.

Conditions causing poor visualization of the iris include the following:

• Corneal oedema
• Corneal opacity
• Flat anterior chamber

Conditions causing synechial closure of the anterior chamber angle include the following:

• Neovascular glaucoma
• Iridocorneal endothelial (ICE) syndrome

Patients who are unable to co-operate include the following:

• Patients who cannot sit comfortably at the laser table
• Patients who cannot keep the head still.

Periprocedural Care

Patient Education/Informed Consent

Initially, informed consent for laser peripheral iridotomy (LPI) is obtained. The indications for the procedure (see Introduction), its benefits, and its complications (see Technique) should be discussed in detail with the patient.

Equipment

To perform LPI, a neodymium: yttrium-aluminium-garnet (Nd: YAG) laser (see the image below), is needed.

Neodymium: yttrium-aluminium-garnet (Nd:YAG) laser.

Additionally, using a contact lens makes the procedure easier. The advantages of doing so include the following:

• The laser energy is concentrated at the level of the iris
• The number of corneal epithelial burns is minimized because the lens acts as a heat sink
• The target structure is magnified with less loss of depth of field than occurs if magnification is simply increased with the slit lamp controls
• The lens acts as a speculum; keeping the eye open minimizes fine eye movements

Patient Preparation

Topical anaesthesia with proparacaine 0.5% is usually adequate for performing LPI. The patient must be comfortable at the laser table, as when a patient is examined at the slit lamp.

Monitoring and Follow-up

At 1 hour after completion of LPI, the intraocular pressure (IOP) should be checked to make sure that it did not increase significantly (i.e., that IOP has not increased by 8 mm Hg or more and that IOP does not exceed 30 mm Hg). Topical prednisolone acetate 1% is given 4 times a day for 5-7 days. AT 1 week, the patient is seen to monitor IOP, to confirm the patency of the iridotomy site, and to check for any significant intraocular inflammation.

At 1 month, the patient is seen again for a complete examination that includes IOP measurement, slit-lamp examination, gonioscopy, and dilated fundus examination. IOP is also measured after dilation. If IOP rises by more than 8 mm Hg, the anterior chamber angle is still occludable, and the patient must be evaluated for other causes of angle closure (e.g., plateau iris).