Eye doctors use a plethora of different tests and procedures to examine the eyes. These tests range from simple ones, like having you read an eye chart, to complex tests, such as using a high-powered lens to visualize the structures within the eyes.
A comprehensive eye exam may take at least an hour and is mostly dependent on the optometrist and the number and complexity of tests required to fully evaluate your vision and eye health.
Here are some eye and vision tests that you should come to expect will take place during a standard comprehensive eye exam:
Visual Acuity Tests
Visual acuity tests are some of the first tests that will usually be done. They are designed to measure the sharpness of your vision. They are done with the usage of a projected eye chart and a small, hand-held chart to measure the acuity of your distance vision and near vision, respectively.
Color Blindness Test
This test is also performed early on throughout the course of the exam. Your color vision is checked to test for any signs of color blindness. It is especially helpful in diagnosing those color vision problems that are hereditary in nature.
The cover test is the simplest and most common method of testing your eye coordination.
You will have to focus on a small object across the room with your eyes being alternately covered while you stare at the target.
While doing this, the optometrist will gauge whether or not the uncovered eye must move to pick up the fixation target. This is grounds for testing for the presence of strabismus, or a more subtle binocular vision problem that could cause eye strain or evolve into amblyopia (“lazy eye”). The test is then repeated up close.
The procedure of retinoscopy is especially useful in obtaining an accurate approximation of your prescription powers.
In retinoscopy, the lights in the room will be dimmed and you will be given a large target (typically the big “E” on the eye chart) to stare at. As you stare at the “E,” the optometrist will shine a light at your eye and flip lenses in a machine in front of your eyes.
Based on the way that the light reflects off of the retina in your eye, the eye doctor is then able to determine your prescription very precisely, if not on point.
This test is especially useful for children and patients who are unable to accurately answer the doctor’s questions.
The retinoscopy procedure underway.
Refraction works hand-in-hand with retinoscopy in allowing your eye care specialist to determine your exact eyeglass prescription.
During refraction, the doctor puts an instrument called a phoropter in front of your eyes and shows you a series of lens choices. He/she will then ask you which of the two lenses in each choice pair looks clearer.
Based on your answers, your eye doctor will continue to fine-tune the power of the lens until reaching a final eyeglass prescription.
The refraction determines any level of hyperopia (farsightedness), myopia (nearsightedness), presbyopia, and astigmatism that your eyes may have.
Autorefractors and Aberrometers
Your eye doctor also may use an autorefractor or aberrometer to automatically determine your prescription. When using either of these devices, you will rest your head on a chin rest while you typically look at a pinpoint of light or other image.
An autorefractor, like a manual refraction, determines the lens power required to accurately focus light on your retina. Autorefractors are especially useful in certain cases, such as evaluating young children who are not sitting still or paying attention, or fail to interact properly with the eye doctor to perform an accurate manual refraction.
There are many studies that have shown that modern autorefractors are very accurate and save time. The autorefraction takes all of a few seconds, with the results obtained from the automated test greatly reducing the time required for your optometrist to perform a manual refraction and determine your prescription.
An aberrometer uses advanced wavefront technology to detect even the most obscure of vision errors based on the way light travels through the eye. Aberrometers are usually used for custom or wavefront LASIK vision correction procedures, but their utility has influenced many eye doctors to start using this advanced technology in their own standard, comprehensive eye exams.
The slit-lamp, AKA biomicroscope, is an instrument that the eye doctor uses to examine your eye health.
The slit-lamp allows your optometrist to get a highly magnified view of the structures within your eyes to thoroughly assess your eye health and detect any signs of infection or disease.
During this test, you will rest your head on the chin rest of the slit lamp and the optometrist will then shine the light of the slit-lamp at your eyes. The doctor looks through a set of oculars (just like an ordinary microscope in a science lab) and examines each part and structure within in turn.
He/she will first examine the structures of the front of your eye, including the eyelids, cornea, conjunctiva, and iris. A special high-powered lens will allow the doctor to inspect the internal structure, such as the retina, macula, optic nerve, and more.
The slit-lamp microscope has so much utility in that it can detect any and all disorders affecting the eyes including, but not limited to, macular degeneration, cataracts, diabetic retinopathy, corneal ulcers.
The Glaucoma Test
Glaucoma tests have several variations, all of which help measure the pressure inside your eyes.
A common glaucoma test is the “puff-of-air” test, or non-contact tonometry, NCT. The NCT test begins with you, as with most of these tests, resting your head on the machine’s chin rest. As you gaze at a light inside the machine, the optometrist or a trained assistant will puff a small burst of air at your open eye. It is completely painless and the tonometer does not come into direct contact with your eye.
The machine will calculate your intraocular pressure (IOP) based on how the eye reacts to the presence of this puff-of-air. High IOP readings indicate that you may be at risk for or already have glaucoma.
Another type of glaucoma test is performed with an instrument called an applanation tonometer. The most common of several versions of this instrument is mounted on the slit lamp.
This test involves the application of yellow eye drops to your eye as a form of anesthesia. Your eyes will have a feeling of slight heaviness when the drops start working. The yellow dye glows when exposed to a special blue light. You will then have to stare straight ahead into the slit lamp while he/she gently touches the surface of your eye with the tonometer to measure your IOP.
As with non-contact tonometry, applanation tonometry is painless. The worst that you may feel is the tonometer probe tickling your eyelashes. The whole test takes all of a few seconds.
Unfortunately, most people are unaware that they have glaucoma until they already have significant vision loss. Thus, tonometry tests are essential to rule out any early signs of glaucoma and protect your eyesight before it can worsen.
This test is an excellent way to gauge to the health of the internal structures of the eyes.
The procedure involves the optometrist applying dilating drops to enlarge your pupils. Dilating drops usually take about 20 – 30 minutes to take effect. The dilation of the pupils increases the eye’s sensitivity to light since more light is getting into your eye. You may consequently experience difficulty with looking at objects up close. These effects can last for as long as a couple of hours and is dependent on the strength of the eyedrop used.
Once the drops have started to take effect, the optometrist will next use various instruments to view the insides of your eyes. It is advised that you bring sunglasses with you to your eye exam in order to minimize glare and light sensitivity on the way home. If you don’t come with sunglasses, then the staff will usually give you a disposable pair for your protection.
Pupil dilation is an extremely important procedure for people with risk factors for eye disease because it allows for the most systematic evaluation of the health of the inside of your eyes.
Visual Field Test
A visual field test is an excellent way for the optometrist to check for the possible presence of blind spots (scotomas) in your peripheral (side) vision. Scotomas are a symptom of glaucoma, which, as you know, is usually unknown until it has progressed to its later stages when much vision has been lost. Therefore, it is highly recommended that you agree to take this test for the sake of your optical health. Analysis of scotomas may also help with identifying specific areas of brain damage that are caused by a stroke or tumor.
Other Eye Tests
In some cases, besides the battery of tests performed during a standard comprehensive eye exam that we have already discussed, your eye doctor may recommend other, more specialized eye tests. Other eye doctors often perform these tests with specific expertise in these areas, such as retinal specialists. These tests are performed based on a referral basis.
About Contact Lens Fittings
It’s important to understand that comprehensive eye exams do not usually include a contact lens fitting, and therefore, you will not be given a contact lens prescription during the course of the examination.
However, if you wear currently wear contacts that were fitted by the same optometrist who is performing your comprehensive eye exam, he/she may issue you an updated contact lens prescription at the end of your eye exam to reflect any changes that were found in your eye health.
A contact lens fitting exam is usually done during a subsequent office visit, when your pupils have not been dilated. While the same optometrist who conducts your comprehensive eye exam can perform this exam, it is possible a different eye care practitioner (ECP) may do it.
Generally, it’s better to have your eye exam and your contact lens exam performed at the same practice. A different ECP may repeat the same exam procedure in order to confirm the results and ascertain that your eyes are healthy enough to wear contacts. A repetition of the eye exam may also incur additional costs. Thus, having both of these procedures performed at the same practice will save you both time and money.
Eyeglasses prescriptions are insufficient to purchase contact lenses. Nevertheless, your prescription power gives your ECP a lead for determining the power of your contact lenses.
If you need or want to go elsewhere for your contact lens exam after having a comprehensive eye exam, be sure to ask if additional fees will be required to repeat testing already performed during your eye exam.