Eye Testing

An eye exam doesn’t have to be daunting if you know what to expect. Learn what happens during eye testing and the options available for you. Optometrists perform different types of eye testing procedures, and these range from basic ones like reading from an eye chart to more intricate tests that involve the use of powerful lens for visualizing structures in the eyes. A simple eye test only takes a few minutes but a complex one can take up to an hour or longer, depending on what your optometrist feels is necessary.


What are Visual Acuity Tests?

These are usually the first test used to determine the sharpness of your vision. They are usually performed using an eye chart and a handheld acuity chart to gauge your distance and near vision respectively.

Color Blindness Test

This is a screening exam that assesses your color vision, and it’s usually done early during an eye examination to check for color blindness. Apart from sensing color vision problems, these tests also inform your doctor of potential eye health issues that could affect color vision.

The Cover Test

Optometrists use many tests to evaluate how well your eyes work together, but the cover test is the simplest and in many cases the most effective. During the test, your optometrist will ask you to concentrate your eyes on an object in the room. You will be asked to cover one of your eyes alternately while looking at the object. As you do this, your doctor will check if the eye that’s uncovered needs to move to look at the object. If that’s the case it could be indicative of lazy eye.


Retinoscopy is a test used for obtaining an eyeglass prescription. During the examination, the lights will be dimmed and you’ll be presented a target (most likely the letter E on a chart). As you look at the letter E, light will be shone in your eyes and lenses will be flipped in front of you. The doctor will assess the way light reflects on your eyes and from there give you an estimation of the prescription required. Retinoscopy is particularly helpful for kids or patients that cannot answer a doctor’s questions clearly.

Refraction Test

The refraction test is the method used by your doctor to determine the exact eyeglass prescription you need. During the test a phoropter will be used to figure out the prescription for your contact lenses or eyeglasses. When you undergo this test your optometrist will place the phoropter in front of you and give you several lens options, and you’ll be asked which of the lens pair looks clearest. Your answers helps your eye doctor fine tune the lens until the appropriate prescription is reached. Refraction is also used to assess your level of presbyopia, astigmatism, myopia (nearsightedness) or hyperopia (farsightedness).

Aberrometers and Autorefractors

Your optometrist may also use an aberrometer or an autorefractor to automatically assess your prescription. With both devices, your chin rest is used to keep your head stable while your eyes are focused on an image or light. An autorefractor is a device that determines how much lens power is necessary for light to center on your retina. These autorefractors also come in handy if young children are involved since they aren’t likely to keep still or interact with the optometrist to get a proper assessment.

Autorefractors are becoming more popular due to their accuracy and because they save a lot of time. Unlike other methods, an autorefractor only takes a few seconds, and the results minimizes the time necessary for your optometrist to evaluate and determine the prescription. An aberrometer on the other hand, utilizes sophisticated wavefront technology to sense even the smallest vision errors by assessing the way light moves in your eyes. The majority of aberrometers are used for wavefront or custom LASIK vision correction processes, but a growing number of optometrists use this device in their eye exams as it’s quite effective.

Slit-Lamp Examination

The slit lamp is a device your eye doctor will use to determine the general health status of your eyes. With this device, your doctor can see the structures in your eyes. The slit lamp, also known as a biomicroscope, offers a magnified and detailed look at your eye so your doctor can check for signs of disease, infection or injury.

During the examination your optometrist will put your chin on the slit lamp’s chin rest. The lamp’s light will be shone on your eyes while the doctor peers through a pair of oculars to examine your eyes. The eye doctor starts by checking the structures in front of your eye like the iris, conjunctiva, cornea, lids and so on. Using a powerful set of lens, your doctor will then examine the interior of your eye including the macula, optic nerve, retina and more. The slit lamp examination is useful for examining a wide array of eye diseases and conditions such as diabetic retinopathy, corneal ulcers, macular degeneration and cataracts.

The Glaucoma Test

There are several ways to test for glaucoma, but they all have the same purpose, and that is to gauge the pressure within the eyes. A tonometer is used to measure this pressure and determine if you have glaucoma or not. One of the more common tests is called “puff-of-air”, or non-contact tonometry (NCT). For the NCT, the exam begins with your chin being placed on the chin rest. You then look in the light in the machine, while the eye doctor or an assistant will puff air in front of your eyes. This isn’t going to hurt and neither will the tonometer make contact with your eye. Your eye’s resistance to the air will be used by the machine to calculate your intraocular pressure (IOP), and the higher the figure the more likely you are susceptible to glaucoma, or already have one.

If you think you have glaucoma and need to undergo eye testing, another option would be the applanation tonometer. This is an instrument usually set on the slit lamp, and for this exam, eye drops will be applied to your eyes. Your eyes will then feel heavy, and you’ll be asked to look into the slit so your IOP can be measured.