What is a Laser?

LASER is an acronym for light amplification by stimulated emission of radiation. Simply, lasers are lamps that shine light of one color in a tightly focused beam of energized atoms. They have different characteristics depending on the type of crystal or gas used to create the energized atoms. Since the light is concentrated in a small area, it can carry a strong 'punch', similar to the power concentrated in the water spout of a fireman's waterhose. However, unlike the water, light can pass through the optics of the eye and reach the back of the eye, where humans see.

The advantages of using lasers to both diagnose and treat eye conditions are plentiful. The laser light can be weaker in power than the lightest feather and act as a sensitive finger measuring surface topography, or powerful as a knife, cutting tissue without causing bleeding. For example, the laser light used in reattaching retinas (pictured at right) passes harmlessly through the eye's lens, but then melts retinal tissue successfully reattaching it to the back of the eye.

In addition, laser images (photographs) of the inside of the eye are not only more detailed, but provide previously unobtainable information. Patients also tend to prefer laser imaging to the standard flash method, since its light is less bright and easier to tolerate.

To follow is a sample of lasers used in the diagnosis and treatment of eye conditions. Shiley faculty members were instrumental in the development of all of these devices.

DIAGNOSTIC/IMAGING LASERS

Retinal Twindye Angiograph: (retinal diseases) A fluorescent dye is injected into the blood stream, illuminating the eye. The dye inside the blood vessels glows, permitting this state-of-the-art camera to image the vessels by a very weak laser. This test allows us to map abnormal circulation, determine certain diseases, and monitor treatment progress.

 

Retinal Tomograph: (glaucoma, macular holes, epiretinal membrane) Similar to a CT scan, this instrument generates a 3-dimensional map of the retinal surface in the back of the eye. Generating highly accurate images allows clinicians to measure subtle changes over time.

Howard Chen. M.D. uses the argon laser to repair

Nerve Fiber Analyzer: (glaucoma) This device measures the thickness of the nerve fiber layer using infrared, invisible light. This may be important as advanced glaucoma is defined by significant loss of nerve fibers.

TREATMENT LASERS

Argon: (retinal holes and tears) The laser allows a surgeon to precisely bond the retina to the wall of the eye, preventing a detachment. This occurs because the laser's tiny burns create adhesive forming scar tissue that helps hold the retina in place.

Diode Laser: (investigational, to stabilize wet macular degeneration) The laser decreases or eliminates "drusen" (metabolic waste products) under the retina, ideally averting the development of blood vessel growth.

Porphyrin Enhanced Laser Surgery: (investigational, for wet macular degeneration) The patient is injected with a special dye that adheres exclusively to the walls of the damaged vessels in the macula. This specially designed laser activates the dye and destroys only the abnormal vessels, leaving the retina untouched.

YAG Laser: (glaucoma and "secondary cataracts") Instead of using heat, the laser makes tiny "explosions" that create openings to treat glaucoma or secondary cataracts.