Laser for the Retina

Laser has been used to treat the retina for more than 50 years, and it has protected the sight of millions of people with diabetes. It is done in the office. There are two main kinds: scatter laser (PRP), which makes abnormal new blood vessels shrink, and focal laser, which seals leaks near the center of the retina. A different laser seals retinal tears.

Choose a kind and press Play.

Scatter laser (panretinal photocoagulation, PRP)

What it treats. When parts of the retina lose their blood supply, as in advanced diabetic eye disease or after a blocked retinal vein, they send out a signal that makes fragile new vessels grow. These can bleed into the gel inside the eye, form scar tissue that pulls the retina off, or grow over the eye's drain and cause a severe form of glaucoma (neovascular glaucoma).

How it works. Hundreds to a couple of thousand small laser spots are placed across the outer retina, avoiding the center. The treated retina uses less oxygen, the signal switches off, and the new vessels shrink. It is usually done over two or three sessions, a week or two apart.

Side effects.

• Some loss of side vision and night vision, because the outer retina is treated. Most people adapt, but it can affect driving in some.
• Blurred vision for a few days, and occasionally swelling at the center.
• It is the price of preventing severe vision loss, and it is permanent protection: treated vessels rarely come back.

Injections or laser? Injections into the eye also make new vessels shrink, without the loss of side vision, but they wear off and must be repeated. Laser lasts. Many people have both. Your doctor will suggest the balance that suits your eyes and how easily you can keep frequent visits.

Focal laser

What it treats. Leaking spots in the small vessels near the macula, causing diabetic macular edema or swelling after a vein blockage.

How it works. A small number of gentle spots are aimed at the leaking points or in a light grid around the area, away from the very center. The leaks seal over the following months.

Today. Injections have largely replaced focal laser as the first treatment for macular swelling, because they work faster and improve vision more often. Focal laser is still used for some leaks, and alongside injections to reduce how many are needed.

The visit

1. Drops dilate the pupils, and numbing drops are placed in the eye.
2. You sit at a laser that looks like the microscope used for your exams.
3. A contact lens is placed on the eye to hold the lids open and focus the laser.
4. You see bright flashes. Scatter laser can sting or ache, especially near the edges of the retina; tell the doctor if you need a break. A numbing injection beside the eye is an option for people who find it painful. Focal laser is usually painless.
5. A session takes about 10 to 30 minutes.

Bring a driver. Vision is dazzled and blurred for the rest of the day. An ache can be eased with ordinary pain relievers.

Afterward

• Keep up your follow-up visits: the effect is checked after a few weeks, and more laser can be added.
• Keep blood sugar, blood pressure and cholesterol under control: the laser treats the result, not the cause.
• Call the same day for a sudden shower of floaters, a curtain over your vision or severe pain. See When to Call the Same Day.

If you have glaucoma

Scatter laser is also an important part of treating neovascular glaucoma, because it makes the vessels growing over the drain shrink. Eye pressure is then controlled with drops, and sometimes with a tube shunt or cyclophotocoagulation.

Questions worth asking

• Which kind of laser do I need, and why?
• How many sessions will it take?
• Would injections, laser or both be best for me?
• Will it affect my driving?