(Guy.txt) The Myopia Story Eye specialists have debated for decades the best way to treat nearsightedness -- the inability to clearly focus distant objects in children. Bifocal glasses, eye drops, eye exercises, and biofeedback have all been tried, but the long-term effectiveness of these treatments is uncertain. A new study supports another approach -- no treatment at all. Youngsters' eyes manage to keep images in focus even as they grow and change shape. For un-blurred vision, light entering the eye must focus on the retina -- the layers of specialized cells lining the eyeballs' back inner surface. If an eye is too long, then images come into focus in front of the retina, a condition known as myopia or nearsightedness. An eye that's too short will focus light behind the retina, causing hyperopia or farsightedness. A report in the August "Nature Medicine" shows that the eyes of young rhesus monkeys change shape in an attempt to focus blurred images. Texas researchers raised 11 infant monkeys with glasses fixed permanently in front of their eyes. The left lens was always plain, flat glass, while the right lens (plus or minus) caused images to focus either in front of the retina or behind it. After three months, one eye had grown more than the other, presumably to position the retina at the proper spot for clear vision. When the spectacles were removed, the monkeys' eyes again grew at different rates and eventually returned to similar lengths, restoring their vision to normal. (i.e., the focal status of the right eye changed to match the left eye.) If visual cues such as poorly focused images signal the eyes to grow or stop growing, then treating myopia with glasses or contact lenses before the eyes stop growing could interfere with this natural correction. We asked Dr. David Guyton, the Krieger Professor of Pediatric Ophthalmology at Johns Hopkins' Wilmer Eye Institute, to discuss how these new findings may change the treatment of myopia in children and young adults. -- The Editors *************** The Physician's Perspective -- David L. Guyton, MD According to old-wives' tales, wearing glasses makes the eyes worse. Generations of ophthalmologists and optometrists have told their patients just the opposite, that the eye's development is predetermined by genetics and cannot be affected by glasses. A growing body of animal and human research, however, suggests that the old wives were right after all. The ability of young rhesus monkeys' eyes to gradually change shape in response to what they see comes as no surprise to vision scientists. Over the past two decades, their studies have demonstrated that the eyes of young birds, tree shrews, guinea pigs, and marmosets react to unfocused images by altering their growth to correct the problem. It is highly likely that the eyes of infants and young children also adapt to what they see. This adaptation occurs by a relative change in eye length that works something like this: As the front of the eye grows and becomes less curved, images focus deeper and deeper within the eye. If the lengthwise growth perfectly matches the change in the eye's other dimensions, then images continue to focus on the retina. If there is a mismatch and the focus is off by even the thickness of this paper, then vision will be blurred. Remarkably, the eye apparently senses where images focus and compensates when needed. If light focuses in front of the retina, the eye will stop lengthening until the images catch up. If the focus is behind the retina, the eye grows in length at an accelerated rate until the retina is "pushed back" to the correct spot relative to the eye's other dimensions. Thanks to this feedback mechanism, the eyes generally maintain clearly focused images throughout early life despite dramatic changes in size. In addition to eye size and shape, the distance between the eye and the objects it is viewing also determines where images focus. Near objects come to focus behind the retina, but the lens changes shape and pulls the images forward until they are clear enough to recognize. However, they often remain slightly behind the retina. This slight mismatch may be the mechanism by which prolonged close work such as reading can signal the eye to grow longer. If such a signal occurs frequently and strongly enough in early life, the human eye may gradually lengthen and become permanently focused for near objects. This produces nearsightedness. Most of the adaptive changes in eye length occur during infancy and youth, while the eye is still growing in its socket. When the front of the eye stops growing, around age nine or ten, any further adaptive change can occur only in the myopic direction -Ä the eye can grow longer, but not shhorter. Activities such as prolonged reading at close distances may cause the eyes to continue lengthening well into one's 20s. If this cycle of incomplete focus and eye lengthening is the primary cause of myopia, how can we intervene in this process? Some practitioners believe that limiting the amount of close-up reading or television watching a child or young adult does each day may prevent myopia. These days that is a difficult task. So I advise parents to encourage children to hold objects and reading materials as far away from their faces as comfortable, and to sit at least three feet away from the television screen. (Those who insist on holding books close to their eyes, or sitting a foot from the television or computer, may already have developed significant myopia or some other problem that warrants a professional eye examination.) For my young patients with simple myopia, I suggest they leave their distance glasses off while reading, something I have always done myself. A child who cannot see the board at school, for example, should wear glasses to see the board, but remove them when reading a book or writing. Prolonged reading without glasses shouldn't stimulate the eye to lengthen any farther than what is needed to comfortably focus the eye at rest at the customary reading distance. By comparison, when one reads through glasses or contact lenses designed to bring the distant world into sharp focus, the page is focused behind the retina. This may prompt another round of eye lengthening with worsening of the myopia. For someone who is quite myopic or has astigmatism, the glasses-off technique is not really feasible. In such cases I often prescribe glasses that correct only part of the myopia, or correct only the astigmatism. This leaves the patient exactly focused for his or her customary reading distance. Since contact lenses cannot be removed as easily as glasses for prolonged reading, wearing full-power reading glasses in addition to contacts may help reduce further increases in eye length. Surgical procedures that correct myopia by reshaping the curvature of the eye, if performed too early in life, will likely have the same effect as wearing glasses that correct for distance only, and the myopia may simply reappear. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Vision Research In Sharpening Children's Focus, Glasses May Fuzz the Future Experiments with monkeys suggest that wearing glasses to correct a vision problem might make a young child's vision worse, researchers announced yesterday. The finding, based on experiments in Rhesus monkeys, indicates that use of corrective lenses actually alters the way that eyes grow -- a finding that could eventually affect the way doctors help fix children's vision problems. "Our results raise important questions concerning how and when refractive errors in young children should be corrected," wrote researchers Earl L. Smith and Li- Fang Hung of the University of Houston and M.L.J. Crawford of the University of Texas graduate school of biomedical sciences in the current issue of Nature Medicine. The research raises the possibility that prescribing glasses for very young children to correct myopia -- nearsightedness -- may make that myopia worse, exacerbating a problem that may have corrected itself over time without medical intervention. Ten percent of children between the ages of 1 and 12 wear glasses, according to the American Academy of Ophthalmology. The researchers, however, did not recommend that parents keep their children's world blurry. "These results do not say 'Don't give them glasses,' " Smith said. "There are very good reasons to prescribe glasses for infants," including prevention of amblyopia, or "lazy eye," and of the muscle control problem known as strabismus. The researchers were quick to caution against drawing other broad conclusions from the study. The monkey measurement period corresponded to the first two or three years of human life and might not apply to children who get their first pair of glasses in grade school, Smith said. "Our results can only be applied with some degree of confidence to very young infants." The researchers suggested that a "partial correction strategy" that leaves vision slightly less than perfect might help the eyes to continue their attempt at self-correction. In the experiment described in the new article, 11 infant rhesus monkeys wore headgear fitted with two lenses: a plain piece of flat glass over the left eye, and a lens over the right that would blur the vision, either to a negative or a positive amount. (The headgear "sort of looks like a very small football helmet," researcher Smith said.) During the 49-day period in which the monkeys wore the spectacles, almost all of those fitted with lenses that simulated hyperopia, or farsightedness, became more myopic; almost all eyes with lenses that simulated myopia became more hyperopic. Earlier studies have shown that chicks fitted with lenses will adjust the growth of their eyes to compensate for the visual shift, but the experimental record in mammals is more mixed. This is the first experiment that shows compensation in higher primates, whose eyes closely resemble those of humans. Because of the genetic similarities between the species, Smith said, "It's usually a fairly good bet that the data will extrapolate" to humans. In an accompanying piece, Josh Wallman, a professor of biology at the City College of the City University of New York, and Sally McFadden, of the department of psychology at the University of Newcastle in New South Wales, Australia, wrote that the monkey experiments pointed to a basic mechanism of "visually guided growth" that is not yet well understood -- but that is somehow able to distinguish between blurred vision caused by myopia and blurred vision caused by hyperopia. "That's the big mystery," Wallman said in an interview. "How can the eye do it?" "Such visually guided growth might go awry if most objects viewed are nearby, as with children who read a lot," Wallman and McFadden wrote. "In this situation the eye might elongate to maximize the sharpness of most contours on the retina, resulting in myopia." Several studies have shown a correlation between myopia and educational level or amount of reading. Eventually, they wrote, the insights into the system of compensation that helps fine-tune the eye's development "may lead us to a way of preventing myopia entirely." =========================== How to Slow or Prevent the Progression of Nearsightedness Courtesy of the American Optometric Association, St. Louis, Missouri It may be possible to prevent nearsightedness, says a New York City optometrist and researcher. Although heredity might play a part, research shows that prolonged concentration on near work plays a significant role in the development of nearsightedness, according to Martin Birnbaum, O.D., a professor at the State University of New York College of Optometry. This opens the door to finding ways to prevent the condition, which affects many Americans and tends to get progressively worse when a minus lens is used. Optometrists have developed several alternatives. "Our eyes are not designed for sustained reading and close work," Dr. Birnbaum explained, "and need to exert extra effort to see to read and do other close work. What often happens is that the eyes adapt to near work and lose the ability to focus clearly for seeing people and things further away. "Nearsightedness usually develops during the school years, starting in third or fourth grade, and extends into the college years. It tends to level off or stop after that, but it can occur or get worse in adults over 30 who have jobs involving a lot of close work," Birnbaum said. Options optometrists have to prevent or slow nearsightedness include: o Specially prescribed bifocal (plus-lens) glasses. These glasses take on part of the near focusing job, so the eyes don't have to work as hard. They frequently slow the progression of nearsightedness and, if prescribed at the earliest stages, CAN PREVENT THE CONDITION. o Rigid gas-permeable (RGP) contact lenses. The nearsighted eye grows longer than a normal eye. Studies show that the RGP contact lens-exerts enough pressure on the eye's front surface, called the cornea, to interfere with this growth process and thus slows the progression of nearsightedness. o Vision therapy. This works for those whose nearsightedness is caused by eye coordination and near focusing problems. It involves following a specially designed program of procedures that teach the eyes how to work together efficiently. Birnbaum said that preventing nearsightedness is important because as the eye gets more nearsighted, it is more susceptible to eye health problems like retina detachment.