Comprehensive Eye Exams

Here are some tests you are likely to encounter during a comprehensive eye exam. Depending on your particular needs, your doctor may perform additional tests or schedule them to be performed at a later date.

Computer Autorefraction

This test utilizes a computer to analyze the optics of your eye. The computer evaluates the way an image is focused on the retina, without the need for you to say anything. This makes autorefractors especially useful when examining young children or people who may have difficulty with a subjective refraction. Automated refractions and subjective refractions are often used together during a comprehensive exam to determine your eyeglasses prescription.

Subjective Refraction

This is the test your doctor uses to determine your exact eyeglasses prescription. During a refraction, the doctor puts the phoropter in front of your eyes and shows you a series of lens choices. He or she will then ask you which of the two lenses in each choice ("1 or 2," "A or B," for example) make the letters on the wall chart look clearer. Based on your answers, your doctor will determine the amount of nearsightedness, farsightedness and/or astigmatism you have, and the eyeglass lenses required to correct these vision problems.

Binocular Vision

While there are many ways for your eye doctor to check how your eyes work together, the cover test is the simplest and most common.During a cover test, the eye doctor will have you focus on a small object at distance and will then cover each of your eyes alternately while you stare at the target. As they do this, eye doctors observe how much each eye has to move when uncovered to pick up the fixation target. The test is then repeated as you focus on a near object. Cover tests can detect even very subtle misalignments that can interfere with your eyes working together properly (binocular vision) and cause amblyopia or "lazy eye."

Slit-lamp Examination

 
The slit lamp is an instrument that the eye doctor uses to examine the health of your eyes. The slit lamp gives your doctor a highly magnified view of the structures of the eye, including the lens behind the pupil, in order to thoroughly evaluate them for signs of infection or disease. With the help of hand-held lenses, your doctor can also use the slit lamp to examine the retina.

Pupil Dilation

 
Your comprehensive exam may include the use of dilating drops. These eye drops enlargen your pupils so your doctor can get a better view of the internal structures in the back of the eye. Dilating drops usually take about 15 minutes to start working. When your pupils are dilated, you will be sensitive to light, because more light is getting into your eye. You may also notice slight blurred vision. These effects are temporary and usually last for three to five hours,  If you don't have sunglasses to wear after the exam, disposable sunglasses will be provided to help you drive home. Dilation is very important for people with risk factors for eye disease, because it allows for a more thorough evaluation of the health of the inside of your eyes.

Tonometry

Tonometry is the name for a variety of tests that can be performed to determine the pressure inside the eye. Elevated internal eye pressure can cause glaucoma, which is vision loss due to damage to the sensitive optic nerve in the back of the eye.

The most common method used for tonometry is the "air puff" test - where an automated instrument discharges a small burst of air to the surface of your eye. Based on your eye's resistance to the puff of air, the machine calculates the pressure inside your eye - called your intraocular pressure (IOP). Though the test itself can be startling, nothing but air touches your eye during this measurement and there's no risk of eye injury from the air puff test.

Another popular way to measure eye pressure is with an instrument called an applanation tonometer, which is usually attached to a slit lamp. For this test, a yellow eye drop is placed on your eyes. Your eyes will feel slightly heavy when the drops start working. This is not a dilating drop - it is simply a numbing agent combined with a yellow dye. Then the doctor will have you stare straight ahead in the slit lamp while he or she gently rests the bright-blue glowing probe of the tonometer on the front of each eye and manually measures the intraocular pressure. Like the air puff test, applanation tonometry is painless and takes just a few seconds.

Since glaucoma is often the result of an increase of pressure inside the eye, these are important tests for ensuring the long-term health of your eyes.