AUTO-REFRACTION (or high-tech retinoscopy)
Ever wonder how that two year-old got her glasses? How did she tell the doctor that she couldn't see? Could she tell the difference between "one or two" and "better or worse"? Not likely. Objective testing, or testing that does not require patient response, is the only method available to optometrists for determining the vision of infants and young children. For that matter, certain handicapped individuals (retarded, deaf mutes, the senile, etc.) rely totally on objective testing. So, what is objective testing? I'm glad you asked.
Retinoscopy is certainly nothing new. Webster says the term has been around since 1884, and describes it as: "observation of the retina of the eye esp. to determine the state of refraction." Sounds simple enough but I'm here to tell you….it AIN'T! We are taught how to do retinoscopy in school, but we don't "learn" it for years. A highly skilled retinoscopist, uh…er… much like myself, can determine your refractive status (prescription) in a little under 20 seconds per eye! Those of you recently in my exam chair might recall staring at a little white spot on the chart while I flashed a streak of light in your eyes. You might remember seeing the spot get blurry and streaky while I rapidly changed lenses in the phoropter. This is the objective procedure called retinoscopy and what I'm doing is "neutralizing" reflected light off your retina. The mechanism is highly technical and I would hate to bore you with details (plus, I would have to look them up), so, just consider it a means by which your doctor can get very close to your prescription without you ever mumbling "better one" or "better two". Now, don't you feel less pressure already?
Enter, the Automatic Refractor. Several companies have now manufactured machines to do retinoscopy automatically. I guess you could call them hi-tech, computerized retinoscopes since their function is the same; to determine the refractive status of the eyes without relying on patient responses. Only this time it is done with infra-red light, rather than visible light. The principle is similar in that the result is determined by optically "measuring" the eye with light, albeit invisible, and arriving at a suitable prescription for the patient. As with regular retinoscopy, you do not actually ARRIVE at a prescription, because many factors go into that, but it should steer you close. A final prescription is determined only after a complete vision analysis, which includes patient history, ocular health assessment, both objective and subjective (patient input) refraction, binocular testing, focusing ability, and a myriad of other things that make up a comprehensive eye exam. But where the subjective tests are nearly impossible, that's where the auto-refractor really shines.
I've been kidded by a few of my patients lately that it looks like I'm being
replaced by a machine. Well, not so fast. Although that new HARK (Humphreys
Automatic Refractor/Keratometer) does a wonderful
job, is accurate 80% of the time, and is quite fun at times, it can also
error….big time! Many younger children and even teenagers will tend to
"overfocus" the starburst target in the
machine and the result is that they can appear to be quite nearsighted. This
has occurred several times, but with my trusty hand-held retinoscope
they will test
Of course the goal in having all this rapidly advancing technology is the same as it's always been: to be able to provide a state-of-the-art examination with the best tools available that will produce the best result for the patient's needs.