Glaucoma laser procedures lower the eye pressure by either increasing the drainage of fluid from the eye or reducing the fluid production into the eye.
In open-angle glaucoma, the drainage pathway is blocked so the fluid does not drain well. A laser procedure called Selective Laser Trabeculoplasty, or SLT for short, can bring about microscopic changes in the drainage pathway, improving the flow of fluid and reducing eye pressure.
For eyes with angle-closure glaucoma, SLT is not appropriate because there is no view of the drainage angle. The angle is too narrow or may be closed, preventing fluid from entering the drainage pathway. This can result in either a gradual or sudden increase in eye pressure.
A procedure called laser peripheral iridotomy makes a small hole in the iris, allowing the fluid behind the iris to flow through, widening the drainage angle and enabling fluid to drain more easily. Laser iridotomy helps to prevent a sudden and significant increase in eye pressure which can be caused by angle-closure.
Another laser procedure, called laser iridoplasty, can also widen the drainage angle by making contraction burns on the iris.
SLT, laser iridotomy, and iridoplasty are all outpatient procedures done in the clinic, so you can go home afterwards. Before the laser, your eye will be numbed with eye drops, and a special contact lens is placed on the eye to focus the laser on either the drainage angle for SLT, or the iris for iridotomy and iridoplasty. These laser procedures are generally very safe. Occasionally, they can result in an increase in eye pressure which is usually short-lived.
On the other hand, cyclophotocoagulation, or CPC, is a laser procedure that reduces fluid production in the eye. It is an outpatient procedure performed either in the clinic or the day surgery theatre. Your eyes will be numbed with an injection around the eye. Intravenous medications may also be given to help you to be relaxed. A laser probe is placed on the surface of the eye, and the targeted laser energy reduces fluid production within the eye, hence reducing eye pressure.
Newer types of CPC are now available, which reduce complications after the procedure and improve safety. Your doctor will discuss the risks and benefits with you in more detail. Besides medications and lasers, glaucoma surgery is also an option to reduce eye pressure.