In our last article, we discussed the 5 most common tests an eye doctor performs in a comprehensive eye exam. In this article we’ll cover the next 5 you can expect from a routine eye exam.
This test may be performed earlier on in your exam to determine an accurate approximation of what eyeglass prescription you will need.
In a retinoscopy, the lights in the room are dimmed, and the eye doctor will indicate that you need to focus on a target which is typically the large “E” that is featured on an eye chart. While you are staring at the target, the doctor will shine a light at each of your eyes and then flip the lenses inside a machine that is positioned over your eyes. This is a test that determines the lens power that will be suitable to correct distance vision.
According to how the light is reflecting from your eyes, your eye doctor will be able to determine a “ballpark” of the prescription needed.
This is a test that is useful for children along with the patients that are not able to answer the questions the doctor is asking.
This test is used for determining exact eyeglass prescriptions. During this test, the doctor uses a phoropter which is a specialized instrument in the front of each eye, where you will be shown a sequence of choices in the lens. You will then be asked which lenses out of two choices appears to be clearer.
According to how you answer, the doctor will carry on fine-tuning the power of the lens until they reach your final prescription.
Refraction is used to determine your levels of farsightedness (hyperopia), nearsightedness (myopia), presbyopia and astigmatism.
- Aberrometers and Autorefractors
Some eye doctors also use either an aberrometer or autorefractor that automatically determines your exact eyeglass prescription. With these devices, the chin rest is used to stabilize your head. You will then look into an instrument at the pinpoint of a light or detailed image.
The autorefractor, similar to manual refraction will determine lens power that is required to focus light accurately on each retina. The autorefractors are particularly helpful to determine a prescription for eyeglass in younger children or for adults that have an issue in sitting still, providing feedback or paying attention.
Studies suggest that the more modern autorefractors are highly accurate. They are also a way to save time. Autorefraction only takes a couple of seconds and results that are obtained from these automated tests reduce time that is required for the eye doctors to perform the manual refractions.
Aberrometers use a wave-front technology that is advanced to locate even the obscure type of vision errors according to the way in which light will travel through each eye. Aberrometers are mainly used for wave-front or custom LASIK vision-correction procedures. However, there are a variety of eye doctors which have now incorporated this technology into routine eye examinations.
- Slit Lamp Exam
This is a biomicroscope or binocular microscope that eye doctors use for examining the structure of the eye under an extremely high magnification. This device looks like the upright and large microscopes that are used in science laboratories.
During the slit-lamp examination, your chin and forehead will be placed securely against rests situated at the front of this instrument. The doctor will then proceed to examine structures at the front of each eye that will include your eyelids, conjunctiva, cornea, lens, and iris.
With a hand-held lens, the doctor might use the slit-lamp for examining structures that are situated farther back such as the optic nerve and the retina.
Many eye diseases and eye conditions are detected with the use of a slit-lamp exam, this includes diabetic retinopathy, cataracts, macular degeneration, and corneal ulcers, etc.
- The Glaucoma Test
The test for glaucoma will usually start by measuring the pressure inside the eyes.
One of the common types of glaucoma tests includes the “puff-of-air” test, which is also called a non-contact tonometry (NCT).
For an NCT, your chin will be positioned on a rest. While staring into a light positioned inside a machine either a trained assistant or a doctor will puff a small burst of air into the open eye. The test is painless, and tonometer will not come into contact with your actual eye.
According to the resistance of the eye to the air, the machine will calculate the IOP (intraocular pressure) in your eye. If the pressure is high, you could either have glaucoma or be at risk.
Other glaucoma tests involve an applanation tonometer which is a specialized instrument. The more common version of these instruments will be mounted on a slit lamp.
In this test, the eye doctor places yellow eye-drops into the eyes to numb them. The eyes will initially feel heavy as the drops begin to work. These are not dilating drops, but rather a numbing-agent that is mixed with yellow dye which glows under blue light. The doctor will ask you to look straight ahead using a slit lamp while she or he touches the eyes surface gently with a tonometer that measures IOP.
Like the NCT, an applanation tonometry is also painless. The most you might feel is a tickle from the tonometer-probe as it touches your eyelashes. The entire test takes a couple of seconds to complete.
You will usually not experience any warning signs that you have glaucoma until already experiencing vision loss that is significant. This is why routine eye examinations which include the tonometry are vital in order to rule out the earlier signals of glaucoma as well as to protect your overall eyesight.
Learn what else is commonly addressed in a comprehensive eye exam in our next article.