Argon laser trabeculoplasty lowers the pressure in the eye about 75% of the time in people who haven't had surgery on that eye before.^{footnote 1} Research comparing ALT and SLT has shown that SLT lowers pressure in the eye about the same as ALT. People usually need to continue taking medicine after laser surgery to keep down the pressure in their eyes.

Control over the pressure inside the eye may decrease as time passes. Argon laser trabeculoplasty is often not effective when repeated. But experts believe that SLT may be repeated because it uses a lower level of laser and causes less scarring than ALT. SLT may be used if ALT fails to lower eye pressure. The results of repeated laser surgeries are less predictable than the results of the first surgery.

Complications of laser trabeculoplasty are rare. The most common complication of laser surgery for glaucoma is an increase in the pressure in the eyes. The pressure may be normal immediately after laser surgery and rise sharply within 1 to 4 hours after laser surgery. To prevent this problem, the doctor may put medicine in your eyes (such as apraclonidine or brimonidine) before or after laser surgery, especially in people with high intraocular pressure before laser surgery.

Other complications of laser surgery may include:

• A brief period of inflammation of the coloured part of the eye (iris).
• Cloudiness of the clear covering (cornea) over the iris. This usually does not last long.
• Blockage of the drainage angle when the cornea and the iris stick together.
• Pain.
• Decreased vision.

Decreased vision is usually a temporary problem unless there is a significant rise in the pressure inside the eye. Very high pressures inside the eye can lead to permanent vision loss.