The newsLINK Group - Refractive Errors

Editorial Library Category: Health Topics: Refractive Errors Title: Refractive Errors Author: newsLINK Staff Synopsis: Eye-care professionals commonly divide refractive errors into two separate classifications: lower-order aberrations and higher-order aberrations. Editorial: Refractive Errors 4064 South Highland Drive, Millcreek, Utah 84124 │ │ (v) 801.676.9722 │ (tf) 855.747.4003 │ (f) 801.742.5803 Editorial Library | © The newsLINK Group LLC 1 Eye-care professionals commonly divide refractive errors into two separate classifications: lower-order aberrations and higher-order aberrations. Lower-order aberrations are the common refractive errors, and they always involve blurry vision. Higher-order aberrations are broader and trickier, since they consist of any aberration away from what is considered to be normal vision. There is obviously some overlap. For example, the symptoms listed for all the common refractive errors are also symptoms for higher-order refractive errors. Today’s eye doctors are deeply indebted to many pioneers for their work in optics and refractive errors, but especially to a Dutch physicist named Frits Zernike who won the Nobel Prize in Physics in 1953 for his work developing a phase- contrast microscope. An early interest in photography led Frits Zernike to a study of optics that began in 1930. As part of that effort, he developed the math behind wavefront measurements in 1934 when he created what is called a Zernike polynomial. The Zernike polynomial is based on a circle. Each polynomial describes one aberration for one specific point on a wavefront. The sum of the polynomials creates a full description of all the aberrations present; this result is called the total refractive error for the eye being tested. Zernike polynomials made it possible to accurately identify lower- order aberrations and higher-order aberrations. The Lower-order Refractive Errors Lower-order refractive errors are broadly classified into four separate problems: Myopia Hyperopia Presbyopia Astigmatism For all of these refractive errors, blurred vision is the most common symptom. Squinting, eye strain, headaches, double vision, a glare or a halo around bright lights, and haziness are other possible symptoms. Common refractive errors are usually corrected with glasses, contact lenses, or laser eye surgery. Presbyopia can be treated by implanting lenses, with LASIK monovision, and by conductive keratoplasty. Higher-order Refractive Errors Symptoms of higher-order refractive errors include the following: Blurry or double vision Ghost images Difficulty seeing at night Glare, halos, and a starburst effect Higher-order refractive errors also include problems caused by cataracts and the scarring on the surface of the eye from eye surgery, disease, or trauma. Most eye doctors used to ignore the higher-order aberrations (including Zernike aberrations such as coma, trefoil, and spherical aberration), in part because it was thought they do not cause serious problems to a person’s vision but — more importantly — also because there was no good method for identification and correction of these problems. As refractive eye surgery has become more common, however, ignoring higher-order aberrations became an increasingly poor choice because these errors make laser surgery less effective. In particular, higher-order aberrations can cause post-surgery physical side-effects. Eye doctors are now taking a more proactive approach as the ability to diagnose these problems has increased, because they also now have a greater ability to treat them. One example of this is the ability to help people see better when they drive at night under low-light conditions. Another important example is the work being done to diagnose dry eye. Dry eye affects 15 to 30 percent of the U.S. population, but more commonly among those who are aging, women, those who wear contact lenses, those who have had refractive surgery, people taking specific medications, and those who use computers. According to the American