What You Need To Know

About an Eye Exam

Visual Acuity Test

Visual Acuity Test measures the sharpness of your vision. These usually are performed using a projected eye chart to measure your distance visual acuity and a small, hand-held acuity chart to measure your near vision.
  • To check for vision loss in any area of your visual field.
  • To screen for eye diseases, such as macular degenration and glaucoma, which cause gaps in the visual field.
  • To look for damage to the nerves of the eye following a stroke, head injury, or other condition that causes reduced blood flow to the brain.
The Snellen Test checks your ability to see at distances. It uses a wall chart that has several rows of letters. The letters on the top row are the largest; those on the bottom row are the smallest.
  • You will stand or sit 20 ft (6 m) from the chart and be asked to cover one eye and then read the smallest row of letters you can see on the chart. If you are unable to cover your eye, an eye patch will be placed over your eye.
  • Each eye is tested separately. You may be given a different chart or asked to read a row backward to make sure that you did not memorize the sequence of letters from the previous test.
  • If you wear glasses or contacts, you may be asked to repeat the test on each eye while wearing them.
  • Let your health professional know if you have trouble reading the letters on one side of the row, or if some letters disappear while you are looking at other letters. You may have a visual field problem, and visual field tests may be needed.
  • 20/20 (feet) or 6/6 (meters) refers as the standard visual acuity scale of normal vision.
  • A person with 20/40 visual acuity would have to get within 20 feet of a letter that should be seen at 40 feet in order to see it clearly.

Visual Field Test

Visual Field Test measures your peripheral vision when your eye lens focuses at one point at distant object and including the Confrontational Visual Field Exam, Tangent Screen Test, and Automated Perimetry Exam.
  • Your doctor will be able to determine if you are having trouble seeing in certain areas of your visual field, as well as possible causes for these difficulties.
  • Identify and analysis the presence of blind spots (scotomas) in your peripheral or "side" vision while performing the test can originate from eye diseases such as glaucoma as well as brain damge caused by a stroke or tumor.


1. Confrontational Visual Field Exam: helps your eye doctor decide if further visual field testing is needed

  • Eye doctor will sit or stand 3 to 4 feet in front of you.
  • You will be instructed to cover one of your eyes using an occluder, which looks like a large spoon and stare straight ahead as he or she moves his or her hand in and out of your visual field.
2. Tangent Screen Test (a.k.a. Goldmann Field Exam): helps determine if there are certain areas in your visual field that you are unable to see that helps diagnose the cause of the visual field problems.
  • You will be seated about three feet away from a computer screen.
  • This screen will have a target in the center for you to focus on throughout the test. The computer will generate images on different areas of the screen.
  • Without moving your eyes, you will tell your doctor when you are able to see objects in your side vision. Your doctor will be able to use the information collected to form a map of your visual field.

3. Automated Perimetry Exam: your eye doctor use this result data to help diagnose problems or order more vision tests
  • You will sit and look into a dome-shaped instrument.
  • Your doctor will instruct you to look at an object in the middle of the dome throughout the test. There will be small flashes of light on the dome. When you see these flashes of light, you will press a button.
  • The computer program will provide your doctor with a map of your visual field.
-Including disorders in the central nervous system or the part of the brain that deals with vision.
-Diagnosis problems such as:
  • Glaucoma
  • Macular Degeneration
  • Optic Glioma
  • Brain Tumor (e.g Alzheimer's)
  • Multiple Sclerosis (MS)
  • Stroke
  • Temporal Arteritis
  • Central Nervous System Disorders
  • Hyperthyroidism (overactive thyroid)
  • Pituitary Gland Disorders
  • High Blood Pressure
  • Diabetes Type 1 or Type 2


Refraction is the third step after your visual acuity test and visual filed test when eye doctor determine your prescription of eyeglasses or contact lenses if you have refractive error in which your vision is not 20/20 (in feet) and 6/6 (in meters)
  • Conducted to determine the appropriate lens power needed for fixing any refractive error (see result)
  • Also help to diagnose and treat refractive errors (see result)
  • Before starting the test, health professional uses eyedrops to widen (dilate) your pupils before you start this test which may take approx. 15-20 minutes for your fully pupil dilation

  • Using Phoroptor (a retinoscope), your health professional may shine light into your eyes. A series of trial lenses will be placed in front of your eyes and adjusted until the light rays are properly focused on your retina.
  • Testing one eye at a time, the health professional will continue to test your eyes with different lenses until it is determined which lenses correct your vision the best.
Results of refractive error:
  • Astigmatism: an abnormal curvature in the cornea that causes blurry vision
  • Hyperopia: farsightedness
  • Myopia: nearsightedness
  • Presbyopia: a condition related to aging that causes lens of the eye to have trouble focusing
  • An ulcer or infection on the cornea
  • Macular degeneration: a condition related to aging that affects your sharp, central vision
  • Retinal vessel occlusion: a condition that causes the small blood vessels near the retina to be blocked
  • Retinitis Pigmentosa: a rare genetic condition that damages the retina
  • Retinal Detachment: when the retina detaches from the rest of the eye

Tonometry (Eye Pressure Measurement)

Tonometry is an eye test that detect changes in eye pressure long before you may be aware of them. The most common type of tonometry test is called "Goldmann applanation tonometry," which for decades has been considered the international gold standard for measuring intraocular pressure (IOP) (M Egli, 2011). There are other methods for eye pressure testing such as, pneumotonometry (alternative type of tonometry) and Tono-Pen.
  • This critical test measure the pressure inside your eyes and detecting eye changes early to determine whether or not you may be at risk for glaucomia.
  • If the test comes back positive, your eye doctor will begin treatments, which can delay the progression of the disease.
  • Your eye doctor will put numbing drops in your eyes so that you don’t feel anything touching them.
  • Once the eye is numb, the doctor may touch a tiny, thin strip of paper that contains orange dye to the surface of the eye to stain it. This helps increase the accuracy of the test.
  • The doctor then puts a machine called a "slit-lamp" in front of you, and you rest your chin and forehead in the supports.
  • The lamp is then moved toward your eyes until just the tip of the tonometer probe touches the cornea. By flattening it just a bit, the instrument is able to detect the pressure in your eye.
  • Your eye doctor will adjust the tension until he or she gets a proper reading.
  • The measurement "mmHg" means "millimeters of mercury", which is a scale used to record eye pressure.
  • A normal test result means that the pressure in your eye is within the normal range (10 to 21 mmHg), and you do not have glaucoma or other pressure-related eye problems.
  • Your doctor will discuss treatment options with you if he or she diagnoses you with glaucoma.

Opthalmoscopy (Retinal Examination)

Opthalmoscopy uses 3 different techniques to look at the back of the eye which is called the fundus, the interior surface of the eye consists of the retina, optic disc and blood vessels

This test may also be ordered if you have conditions that affect the blood vessels, such as high blood pressure or diabetes

The test is used to screen for eye diseases and conditions affecting the blood vessels.

  • Your doctor may use eye drops to dilate your pupils. This makes them larger and easier to look through. However, these eye drops can make your vision blurry and sensitive to light for a few hours.
  • You should bring your sunglasses to your appointment which will protect your eyes from bright light while your pupils are dilated, arrange to take the rest of the day off if your job required clear vision skill and have someone to drive you after the test.
  • Tell your ophthalmologist if you have an allergic reaction with eye drops as well as your family history of eye disease you might have.

-Direct Examination:
  • You will be seated in a chair. The lights in the room will be turned off.

  • Your ophthalmologist will sit across from you and use an ophthalmoscope to examine your eye.

  • An ophthalmoscope is an instrument that has a light and several small lenses for your ophthalmologist to look through. Your ophthalmologist may ask you to look in certain directions as he or she looks at the back of your eyes.

  • The bright light may be slightly uncomfortable and cause afterimages to appear. However, it should not cause pain.

-Indirect Examination: allows your doctor to see the structures in the back of the eye in more detail.
  • You will be asked to lie down or sit in a reclined position.
  • Your ophthalmologist will have a bright light positioned around his or her forehead that will be shined in your eyes. A lens will be held in front of your eye. Then your doctor will hold your eye open to look into it.
  • You may be asked to look in certain directions. Pressure may also be applied to your eye with a small, blunt, probe. This may be uncomfortable but should not be painful.
-Slit-lamp Examination: same as indirect examination, but with higher magnification.
  • You will sit with an instrument in front of you. There will be a place for you to place your chin and rest your forehead. This helps keep your head steady during the exam. A bright light will be turned on in front of your eye. Your ophthalmologist will use a microscope to look at the back of the eye.
  • You may be asked to look in different directions. Your ophthalmologist may use his or her finger to open your eye to get a better view. A small, blunt probe may also be used to apply pressure to the eye.
  • This examination may be uncomfortable, but it should not be painful. You may see afterimages after the light turns off. They should go away after blinking several times.
-Use to treat or diagnose with eye problems such as:
  • Diabetes
  • Glaucoma (excessive pressure in the eye)
  • Hypertension (high blood pressure)
  • Macular Degeneration (loss of vision in the center of the visual field)
  • Melanoma (a type of skin cancer, in the ey)
  • Cytomegalovirus (CMV) ( retinitis, an infection of the retina)
  • Damage to the optic nerve
  • Retinal Tear or Detachment