For Patients

What is glaucoma?

Glaucoma is an eye disease in which the optic nerve—the nerve that connects the eye to the brain—deteriorates. This deterioration is slow and painless, but if it is not treated it can lead to vision loss or even blindness. The cause of glaucoma is unknown. The most important risk factor is high eye pressure, which causes the optic nerve deterioration. Glaucoma can be treated by lowering eye pressure but cannot be cured.

How is glaucoma treated?

The eye pressure is high because glaucoma clogs the drain of the eye, blocking the outflow of eye fluid so that fluid builds up in the eye and raises the eye pressure. Lowering the eye pressure prevents further optic nerve damage. Some people have high eye pressure without any glaucoma damage; this is called ocular hypertension, and over time it may turn into glaucoma. Lowering eye pressure in eyes with ocular hypertension can prevent the development of glaucoma.

Eye pressure can be lowered using eye drop medications, laser therapy, or surgery. Most people who are diagnosed with glaucoma start with medications or laser therapy as their first treatment. A recent research study showed that laser therapy is as effective and safe as medical therapy in people with newly-diagnosed glaucoma or ocular hypertension. Treatment with laser therapy avoids the hassles and side effects of putting eye drop medications into your eyes one or more times a day forever.

What is SLT laser therapy?

Laser therapy for glaucoma—called selective laser trabeculoplasty, or SLT—is a treatment in which light energy is applied to the drain of the eye to unclog it. As a result, eye fluid can flow out of the eye and bring down the eye pressure, preventing further damage to the optic nerve. SLT is performed in the doctor’s office during a routine visit. The procedure is performed in the sitting position and only requires numbing eye drops for anesthesia. A contact lens is placed on the eye so the doctor can see clearly into your eye and approximately 100 laser light applications are applied to the drain of the eye.

SLT takes approximately 5 minutes per eye. It may be mildly uncomfortable but is not painful for most people. SLT lowers eye pressure in about 9 out of 10 people. Side effects of SLT are mild and include brief discomfort during the procedure and soreness in the eyes for 1-2 days afterward. In rare cases, eye pressure might go up immediately after the treatment; it usually comes back down quickly with a single drop of medication. SLT’s effect on eye pressure is not permanent, because over time glaucoma reclogs the drain of the eye and eye pressure goes back up. This usually occurs several years after SLT, at which time it can be repeated to unclog the drain again. SLT can be repeated several times as needed when it wears off, but eventually most eyes stop responding to SLT and have to start using eye drop medications to control eye pressure.

What is COAST?

COAST—which stands for Clarifying the Optimal Application of SLT Therapy—is a new research study to see if there is a better way of doing SLT laser therapy than the way we’ve done it for the past 20 years. We believe that SLT repeated once a year at low energy can help people avoid the need to use eye drop medications for a longer time than standard energy SLT repeated only when the eye pressure goes back up. COAST will compare these two approaches to repeat SLT in people who have just been diagnosed with glaucoma or ocular hypertension and have never been treated before (or treated for only a brief time). If you have received medications for more than 6 months, or laser therapy, or surgery for glaucoma, you will not be able to participate in the COAST trial. If you have recently been diagnosed with mild or moderate primary open-angle glaucoma or high-risk ocular hypertension and your doctor has recommended treatment, you may qualify to participate in the COAST study. You may contact the COAST research team at to see if there is a COAST research center near you.