A common concern for some of my patients is if they don’t tell me the correct choice of lens, then their prescription for that year will be off and not work properly. This is not true. When an optometrist is switching between lenses (which we in “the business” call a refraction), we are fine-tuning a prescription using the patient’s input to find the lenses that are the most clear and comfortable.
Optometrists are trained to filter out incorrect answers from our patients as we double and sometimes triple check on your responses to make sure we have the right powers. Many optometrists do this by bracketing the lens choices presented to patients. Bracketing means we pick two lenses with a noticeable difference in powers and move towards the most clear of the two. By doing so, the lenses in 1 and 2 may end up being the same lens or lenses in choices 7 and 8, etc.
Additionally, when we bracket the lens choices our goal (or “end point”) is when the two choices look just about the same. So if your optometrist is checking your eyes and the two choices look about the same, tell them- that’s what we want to know.
Another thing that we as optometrists don’t want is to give you a glasses prescription that are too strong for you. That is why it is important for you to relax and try not to squint when your optometrist is checking your prescription. If you are constantly squinting when we try to refract you, then you are more likely to end up with glasses that only work well when you squint, but are too strong for you when you don’t.
Something I have found to help patients give better responses is remembering to blink often. Occasionally, a patient will get so fixated on telling me which lens looks better that they don’t blink as often as they normally would. This can cause your tear film on the surface of your eyes to start to break up and affect your ability to tell which lens looks better. Blinking often lets your eyelids put a smooth layer of tears over the front of your eyes. It is similar to polishing a lens, and a polished lens is always easier to see out of than a scratched lens.
Your optometrist can check on the health and structures of your eyes as well as check the function of your two eyes working together when you go in for your annual eye exam. The art of determining a person’s prescription is not easy, but an optometrist is trained to work with the responses of their patients. Don’t worry about getting it wrong! If you just remember some of the tips mentioned above, you can be sure your optometrist find your proper prescription.
~Ranjeet S. Bajwa OD
California Optometric Association