Hyperopia, or farsightedness, means that distant objects appear clearer than objects up close. Dr. Patel, can you tell us more about hyperopia?
Of course, Dr. Reynolds. In cases of hyperopia, light rays are not refracted enough, and the resulting image focuses on a point behind the retina instead of on the retina. This happens because the eye is too short or the cornea is too flat.
Younger eyes have a natural accommodating, or focusing, power that often compensates for farsightedness. But eyes become less able to accommodate as they age, which means that hyperopia most commonly becomes a problem later in life. A person with hyperopia may need no correction until they reach their forties or fifties.
Hyperopia can be corrected by any method that increases the total refractive power of the eye. Eyeglasses and contact lenses accomplish this by putting “positive” lenses in front of the eye. “Positive” lenses are thicker in the center than at the edge. Refractive surgery to correct hyperopia makes the central part of the cornea more steeply curved to allow the image to focus on the retina.
One procedure used by the Air Force to treat refractive errors is known as PRK, which stands for “photorefractive keratectomy.” Like other types of refractive surgery, the goal of PRK is to reshape the cornea so that light traveling through it is properly focused onto the retina. Dr. Flemings, can you tell us more about photorefractive keratectomy?
During the procedure, a numbing drop is placed in the eye, the area around the eye is cleaned, and an instrument called a lid speculum is used to hold the eyelids open. The next step is to remove the central epithelium using one of several techniques. An excimer laser, which delivers a pulsing beam of ultraviolet light, is then used to reshape the stroma of the cornea.
The procedure takes about 10 minutes for both eyes. In a relatively short time after the procedure, usually three to four days, the epithelium will heal over the exposed area.