The machines that opticians and optometrists use for checking your eyesight have a lot of strange names. Refractive lenses, autorefractors, tonometers, phoropters, slit-lamps, aberrometers, retinoscopes. They all serve a purpose. All tools might not be needed every time you visit a practice.
It is highly recommended to check the vision of children once a year. That will make it possible to discover potential visual problems at an early stage.
For elders, it is recommended to do an eye exam on a yearly basis to identify macular degeneration, check the eye pressure, and check for cataract.
There is really only a period (typically between 20 and 40 years old) where visual checks could be done every two years or so (unless there is a known condition and/or recommendation to do checkups more regularly).
So, how do they test your eyes? This is a simple list of tests that might be performed. Please note that all practices do not do it in this order, but the main steps are pretty much the same:
- You will be asked questions about your health, like blood pressure, known diseases, family history, etc. Some of these conditions can affect eyesight in both the short and long term. Your type of work and lifestyle can also influence eyesight. The questions are asked because then they know what to look for.
- You will be asked about your present glasses if you have any. Bring them to the practice. What is your experience?
- The next step could be the autorefractor. You rest your head against a chin rest and look into the machine, which shows light or an image. The machine determines the lens power needed to focus light onto the retina in the back of your eye. The machine delivers an accurate prescription, although it needs to be fine-tuned.
- Instead of an autorefractor, it is possible to use a retinoscope, which is a manual instrument to measure refraction with. It is put in front of your eyes and test which lenses give you the clearest image. The lenses are fine-tuned until a correct prescription is found. This determines your level of far-sightedness, near-sightedness, and astigmatism.
- Then the visual acuity test, the standard test where you read letters from a distance of 20 ft (5-6 m). This is done with your previous prescription, to begin with, to determine where to start adding lenses.
- Then your Eye Care Professional will adjust the prescription. This is the moment when he will ask you whether you see "better with this lens or that lens" and, based on your answers, your prescription will be accurately adjusted to the ideal fit; to make it simple, it will be the one that provides you the best visual acuity with the most comfortable feeling.
- Now it could be time for the tonometry test. A puff of air is blown into your open eye. The machine calculates the eye pressure based on your eyes' resistance to the puff. It is a non-contact and completely pain-free test. The eye internal pressure is a good indicator of possible glaucoma.
- The slit-lamp exam will show if there is any damage to the structures of your eyes. You rest your head in a chin rest, and a microscope will be used to check the front of your eye, iris, cornea, eyelids, etc. By using a handheld lens, the back of your eye can be checked with the same instrument. It will show what your retina and optic nerve looks like.
- A visual field test might also be done. It is simply showing if there are any blind spots in your peripheral (side) vision.
Eyes are rather complicated parts of our bodies hence the number of tests above. Each step serves a purpose, and that is to make you see in the best possible way.
Call your practice and take the test at least every second year. Maybe every year if you have passed 50 years of age. Any changes will be detected, and if necessary, you will receive an updated prescription. The time and money invested in this are worth it. For sure.