BACKGROUND: Conventional laser approaches to treating diabetic retinopathy -- a leading cause of blindness in adults -- can feel like getting poked in the eye. But a new technique called Patterned Scanning Laser (PASCAL) aims to make treatment of this common condition less painful and much faster. The technique can also be used to treat other retinal diseases, such as age-related macular degeneration.
ABOUT THE DISEASE: Diabetic retinopathy blocks blood vessels in the retina, the light-sensitive tissue in the back of the eye. As the retina struggles to maintain its blood supply, it begins to grow new but very fragile blood vessels. These thin vessel walls can tear, leaking blood and fluids. This clouds the vision, and can create "floaters" or large blood spots. Left untreated, the disease will cause blindness.
LASING A PATH: Conventional laser eye surgery uses a pulsed, tightly focused beam of light to burn away the abnormal blood vessels before they have a chance to burst, killing part of the retina cells in order that the rest may live. By controlling the size, position and number of laser pulses, the surgeon can control how much tissue is removed. The surgeon uses a joystick to aim the laser and a foot pedal to shoot the pulses, generating rectangular or circular patterns of 20 to 60 laser burns at the edge of the retina. It can take up to four 15-minute sessions to apply the 1000 to 2000 laser burns needed to complete the treatment. With PASCAL, the surgeon can complete the entire procedure in less than five minutes because a computer program automates the laser burn patterns so that doctors can apply the entire pattern with a single shot. It is also less painful because the laser bursts don''t last as long, thanks to PASCAL's improved controls. The heat from the laser has less time to build up in the tissue and diffuse into the layer of nerve cells
HOW LASERS WORK: "Laser" is an acronym for Light Amplification by Stimulated Emission of Radiation. It describes any device that creates and amplifies a narrow, focused beam of light whose photons are all traveling in the same direction, rather than emitting every which way at once. Lasers can be configured to emit many different colors in the spectrum, but each laser can emit only that one color. There are many different types of laser, but all of them have an empty cavity containing a lasing medium: either a crystal like ruby or garnet, or a gas or liquid. There are two mirrors on either end of the cavity, one of which is half-silvered, meaning that it will reflect some light and let some light through. In a laser, the atoms or molecules of the lasing medium are "pumped" by applying intense flashes of light or electricity. The end result is a sudden burst of so-called "coherent" light as all the atoms discharge in a rapid chain reaction.