A laser beam is made of light of the same color (wavelength) and the light is synchronized so the beam is very focussed (coherent). Lasers are useful in treating retinal diseases. Anything you can see inside the eye you can treat with a laser. Laser treatments fall into two major categories: laser used to seal up leaking blood vessels and lasers used to create an adhesion to tack down the retina.
Types of lasers
We use blue, green, yellow, and red lasers to treat the retina. These color lasers are all useful for treating leaking blood vessels or tacking down the retina. Other lasers used in ophthalmology (the eye) but not by retina specialists inlcude YAG laser to open membranes in the eye, excimer laser to shape the cornea, and argon laser for glaucoma. Retina specialists also use photodynamic laser which is a combination laser drug treatment. A drug (visudyne) is injected into an arm vein. Once it reaches the eye, it can be activated with a low energy red laser to seal up abnormal and leaking retinal vessels. It is useful in macular degeneration and also to treat some choroidal tumors and in central serous retinopathy.
Macular Degeneration Laser
Although we usually use intravitreal injections of drugs for macular degeneration, laser treatment is still sometimes helpful. If a leaky blood vessel is affecting central vision because of fluid leaking under the retina, but the blood vessel itself is far from the central vision. Laser can be safe and effective. The below scan shows such a patient with fluid under the central retina before laser (vision 20/200) and then a normal looking central retina after laser (vision 20/20). This patient's vision returned to normal and she has needed no further treatments since and that was in 2005.
Laser for Diabetic Retinopathy
Diabetic Macular Edema: Most commonly, diabetics can lose vision from leaking blood vessels near the central vision. These eyes are treated with focal laser to the leaky vessels. This treatment improves vision half the time and prevents further vision loss most of the time. The below case shows a fluorecein angiogram of an eye with diabetic macular edema before laser and then a color map of the retinal thickness before and 2 months after laser treatment:
Proliferative Diabetic Retinopathy: Diabetics, because of poor circulation to the retina, sometimes develop new and abnormal vessel growths in the eye. These abnormal vessels cause bleeding, scarring, retinal detachment, and can lead to severe and permanent vision loss. Patients with these vessel growths have Proliferative Diabetic Retinopathy and are treated with heavy laser to the peripheral or side retina. This laser can save the eye and preserve central vision. It sometimes causes a loss of peripheral vision and the pupil size can get a little bigger after this laser.