Glaucoma Laser: SLT and Iridotomy

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Two different lasers are commonly used in glaucoma. Selective laser trabeculoplasty (SLT) improves the eye's natural drainage to lower pressure in open-angle glaucoma, and can replace or reduce eye drops. Laser peripheral iridotomy (LPI) makes a tiny opening in the iris to prevent or treat angle-closure glaucoma. Both take a few minutes in the clinic.

SLT (selective laser trabeculoplasty)

• Used for open-angle glaucoma and high eye pressure, either as the first treatment or added to drops. The LiGHT trial showed SLT works as well as drops as a first treatment for many patients, with fewer drops needed.
• A contact lens is placed on the numbed eye and you see flashes for 2 to 5 minutes. It is painless for most people.
• Pressure falls over 4 to 8 weeks. The effect lasts several years in many people and can be repeated.
• Side effects: mild ache, redness or blur for a day; a short rise in pressure, which is checked an hour later.

Laser peripheral iridotomy (PI)

• Used for narrow angles, angle-closure suspects and after an acute angle-closure attack, usually in both eyes.
• Pilocarpine drops make the pupil small first. A lens is placed on the eye and the laser makes a tiny hole near the edge of the iris, usually under the upper lid.
• You may feel a few sharp clicks. It takes a few minutes per eye.
• Afterwards: blur and light sensitivity for a few hours, and steroid drops for a few days. Rarely, people notice a line of light or glare.

After either laser

• Continue your glaucoma drops unless your doctor changes them.
• You can usually return to normal activities the next day; arrange someone to drive you home.
• Keep the follow-up visit: the pressure and angle are checked to see how well the laser worked.

Contact us urgently if

• Severe pain, nausea or headache with blurred vision and haloes
• Vision that is much worse than before the laser

Frequently asked questions

Related: Glaucoma Clinic in Ahmedabad: Tests, Drops & Laser, Glaucoma Eye Drops, Eye Pressure Test (Tonometry).

This leaflet gives general information and does not replace advice from your own eye doctor. Reviewed by Dr. Dhaval Patel, MD (Ophthalmology, AIIMS New Delhi), November 2026.