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Home » Eye Diseases » Understanding the Process, Part 2: Preliminary Testing

Understanding the Process, Part 2: Preliminary Testing

Lets continue on our adventure in exploring the eye exams process!  Once you have been checked in to the clinic for your appointment time, they will most likely run you through a series of tests before you see your optometrist.  These tests can certainly vary from clinic to clinic, but will likely not deviate much from the norm.  We are going to touch on a few of those basic main preliminary tests that you will likely do.


LERC09 000If you already have glasses, you will be asked to bring them in to your exam so the doctor can see what correction you have been wearing, and how close it is to what you would actually need to see crisp and clearly.  A manual lensometer looks kind of like a weird microscope, and by using a combination of dials and light, we can use this to actually read what prescription your lenses are made for.  The manual lensometer may be more difficult for some people to use as it does take some needed training and can take some time if the person using the lensometer is not very proficient at using it.  Therefore, many office have now included the use of an auto-lensometer, which will read the lenses automatically for you and print out the closest average prescription in those lenses.  Manual and Auto lensometer's are not always bang on to the exact written out rx from your doctor for many reasons, so this is a general guideline for the prescription. You cannot take a measurement from a lensometer of any kind and use it to fill new lenses because of this discrepancy.  You must have a valid prescription from an optometrist to fill your glasses prescription.

Auto-Refractor aka Auto-Refkeratometer

The Auto-refractor, also known as an auto-refkeratometer, is a very standard practice among clinics, and it is very unlikely this test will not be used.  While you stare inside the little machine you will see a scene such as a sailboat on the water, or a hot air balloon in the sky. As you watch (one eye at a time) this little scene inside the device, you will notice it start to go in and out of focus on you, and that is exactly what it is designed to do.  As the image goes in and out of focus, the device is taking measurements of the shape and size of your eye and corneal measurements.  With these measurements it can generalize an average likely prescription that you will require.  This is not the visual prescription itself, but more of a starting point for the doctor to work with, to then fine tune and perfect your needed visual correction.  Once again, this is an average measurement, and this should not be taken as a valid prescription, it cannot be used to fill new lenses.

Visual Field Test

This has become a pretty standard test for pretty much all optometrists offices in one way or another, as it is a very important test for maintaininghumphrey fdt perimeter 19004 400×300 retinal health and can be the first signifier that something could be changing in the eyes. This test will be done one eye at a time, you will look inside the machine and will  be given a button to click whenever you see either the jiggling bars or the flashing lights, depending on which visual field test is being done.  This test can last anywhere from a minute per eye for a image assetfaster screening, or up to 10 mins per eye for a full threshold test.  You may find when doing one eye, the other may feel it is going black on you, but don't worry! It is likely only going to happen when testing your non dominant eye.   Your brain prefers to rely on your dominant eye, so when it is covered and the non dominant is not, your brain may try to superimpose the black image over to your non dominant eye.  The best way to ignore this is to blink frequently through the test.  I like to tell my patients to try and blink any time they hit the button, this will hopefully keep them blinking enough to combat this brain effect.

OCT aka Ocular Coherence Test

The OCT (or the ocular coherence test) is a newer development in eye care testing in the last 10 years or so. More and more clinics are lumping these OCT tests in with regular testing now, as before they were mostly only done if your doctor suspected a problem.  Nowadays, doctors are finding the OCT is an important feature of maintaining and monitoring retinal health.  The OCT is basically a scan or xray of your eyeball, giving us a layered and detailed scan of any possible defects, anomalies or anything of note in the back of the eye.  Especially important for anyone with high myopia or patients with Narrow angles, the OCT scan can offer a visual record of how your eye tissues are right now, and having that visual representation from years passed can really help a doctor to determine if and when there are any changes to the back of your eye.

Itra-Ocular Pressures check


This is an extremely important test and measurement for the ongoing health of your eyes, as a high or super low pressure can indicate some very serious eye diseases.  Most offices will do this during pretesting, either by hand held tonometer or by non contact tonometer (that "puff of air" test).  Some doctors will prefer to use the manual contact tonometer in the exam room, especially if they are monitoring for any of those pressure related eye diseases, but this is not always common practice any longer.  Even in an ophthalmologist appointment, you will find that the technicians take most of those measurements now a days.

Optos Eye Scan (and other Retinal Imaging)

The Optos Eye scan is some of the newest technology to be introduced into the eye care world.  The Optos takes full retinal imaging of the back of your eye and maps out many layers in fine details, giving your doctor a literal map of the back of your eye. This retinal imaging enables eyecare professionals to discover, diagnose, document and treat ocular pathology that may first present in the periphery of your eye - pathology which may go undetected using traditional examination techniques and equipment. The newest Optos scanning machine can produce a 200°, single-capture retinal image of unrivaled clarity and can display a six-image overview including color, AF, and OCT of both eyes in as little as 90 seconds. This makes the Optos Eye Scan in the top percentile of eye scanners that are available today.


This is by no means a comprehensive list of all the available preliminary testing you may have in your optometrist or ophthalmologists office, but it does cover the most likely basics.  The actual exam fees may be higher or lower from one doctors office to another, and as a general rule, the more the eye exam costs, the more preliminary tests and thorough testing you will be receiving.  This is why it is not necessarily the best idea to go to a clinic with the least cost for an exam, you may not be getting some important scans and tests done that you should be!  Always discuss with your optometrists office what preliminary testing they will be doing if you are going to see a brand new clinic and doctor for the first time, so you can be sure you are getting the best standard of eye care available!

Stay tuned for the next series in these blog posts, we will take you through the eye exam itself!

Auliya Wilson
Licensed Optician #2557

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