Lasers are devices of modern technology capable of producing high-energy light beams that can be used for some types of surgery. There are also low-energy lasers that have many other practical uses, from measuring the visual acuity of patients with cataracts to reading bar code labels at grocery checkout counters.
Each type of laser is named for the substance used to create its light energy. Those used for treating eye problems derive their power from argon, helium and neon, carbon dioxide, krypton, ruby, yttrium-aluminum-garnet (YAG), or other sources. Each one creates a different color light beam, which affects different eye tissues in different ways. Thus, no one laser can be used for every purpose.
Lasers and Eye Surgery
Lasers offer significant advantages in many types of eye surgery. Since the light can be focused precisely on extremely tiny structures, it can make much finer surgical cuts than are possible with a scalpel. Often, no incision on the eye is necessary, so laser surgery minimizes the risk of infection and the problems related to wound healing. Most laser surgery is painless.
What Does a Surgical Laser Do?
To cut or burn tissue, laser energy must first be absorbed by the tissue. How much energy is absorbed depends on its pigmentation. Argon, ruby, and krypton laser beams, for example, are absorbed mainly by dark tissue, and pass harmlessly through clear structures to reach the back of the eye for retinal surgery.
How Are Lasers Used for Diabetic Retinopathy?
Patients who have had diabetes for a long time, especially insulin-dependent diabetes, are subject to diabetic retinopathy, a condition with problems caused by leakage, blockage, or bleeding from the tiny blood vessels in the retina. As the retinopathy progresses, abnormal new blood vessels can grow along the surface of the retina, and later into the vitreous (gel-like fluid in the center of the eye). If those blood vessels rupture and bleed, they can obscure vision, cause scarring and retinal detachment, and lead to further decrease or even total loss of vision in the affected eye.
When there is evidence of retinal edema (swelling) or growth of new blood vessels along the surface of the retina or into the vitreous, laser surgery on the retina may improve the retinopathy.
How Is Laser Surgery Performed?
Laser surgery is convenient. It may be done either in the doctor's office or in the outpatient eye department of a hospital or clinic, and does not require hospitalization or general anesthesia.
You will be comfortably seated in front of the laser instrument. It is helpful for you to stay calm nd not move during the treatment, so your head may be steadied by the doctor's assistant. Sometimes a local anesthetic is injected behind the eye to keep it from moving during the treatment.
The doctor directs the laser beam by looking through a slit lamp (clinical microscope) at the area being treated. Each time the laser is "fired," you will see a flash of colored light and hear a quick tapping sound. A special type of contact lens called a gonioscope will be held against the eye so the beam can be focused more accurately. Following the treatment your eye pressure may be checked, since the pressure sometimes increases temporarily after surgery. You may need to use eyedrops at home until the pressure returns to normal.
Risks and Prognosis
Surgery of any type involves some risk, and this includes laser surgery. A laser is "strong medicine" that can do harm as well as good. Each laser shot to the retina creates a tiny burn that, if successful, can stop abnormal leakage or bleeding and generally improve the retinopathy. But the scars from the burns also cause a small loss of function. Every effort will be made to keep visual loss to a minimum, but the results are not entirely controllable. Infrequently, a small retinal shrinkage (or "pucker") occurs that can distort vision. You will have to weigh the chance of obtaining a successful result against the risks.
The laser surgery is not guaranteed to be the only or final treatment required. While it may be very successful in arresting the progress of the condition, the benefit may be partial or only temporary. Even if vision does not improve, it is hoped that it will worsen no further. Severe and advanced cases may require a major operation on the vitreous gel and retina in an attempt to save vision.