Eye Tests and Exams
Here's a brief guide to the special eye tests your eye doctor may perform during an eye exam. In addition to a complete examination of your eye, your doctor may want to order one of the following eye tests.
This eye test helps doctors diagnose glaucoma by measuring the amount of pressure needed to flatten a portion of the cornea. This is done by taking a thin strip of paper stained with the dye flourescein. This dye stains the front of the eye and enables a better eye exam by the doctor. The patient is then given a local anesthesia in the form of drops and the pressure is measured using a tonometer.
During this eye test, a computer is used create a "map" of the curvature of the cornea. The computer analysis will show any distortions of the cornea such as scarring, as well as conditions such as astigmatism . This eye test is used to screen patients before they undergo any refractive surgery , as well as for fitting contact lenses and corneal transplants.
This is an eye test used to evaluate the blood circulation in the retina. It is useful in helping diagnose diabetic retinopathy and retinal detachment . During this eye test, a special dye, called fluorescein, is injected into a vein in the arm. The dye quickly travels to the blood vessels inside the eye. Once it reaches the eye, a specialized camera equipped is used to photograph the fluorescein as it circulates though the blood vessels in the back of the eye. This will enable the doctor to diagnose any circulation problems, swelling, leaking or abnormal blood vessels.
Pupillary Dilation Test
During this eye test, the eye doctor places special drops in the eye that cause the pupil to dilate (expand). By dilating the pupils, your doctor can examine your retina for any signs of disease.
This eye test measures your ability to see objects at specific distances. Often doctors will ask the patient to look at a chart, usually 20 feet away, and try to read it while looking through a special instrument known as a phoropter. The phoropter moves lenses of different strengths into place for the patient to look through. This eye test is useful in helping to diagnose presbyopia, hyperopia, myopia, and astigmatism.
This eye test looks at the front of the eye by shining a beam of light shaped like a small slit on the eye. The eye doctor may also dilate your pupils while you are undergoing this eye exam. The eye test can be used to help diagnose cataracts, retinal detachment, macular degeneration, injuries to the cornea and presbyopia.
An eye test used to help diagnose glaucoma in which a small, smooth instrument known as a tonometer s lowered onto the surface of the eye in order to measure the pressure in the eye.
An ultrasound eye test uses sound waves to provide a picture of the eye's internal structure. It is useful in evaluating ocular tumors as well as the retina when it is being obscured by cataracts or a hemmorhage. This eye test will be given as part of preoperative evaluation for cataract surgery.
Visual Acuity Testing
A test of your visual acuity, or ability to see sharply and clearly at near and far distances, will be performed. Various eye tests can be used to determine the visual acuity of infants, children, and adults. These are fairly simple and can be performed by an ophthalmologist, optometrist, technician, nurse, or optician. They do not, however, test for important functions of sight, like depth perception or color blindness. One common type of eye test used for children who cannot yet read is the Random E's Visual Acuity Test. The patient is asked to identify the direction that the letter "E" opens to by holding out 4 fingers to mimic the letter "E." This eye test is safe, there are no risks involved, and it works just as well as most other eye tests.
Visual Field Test
A test used to measure peripheral (side) vision. When given this test, you will be asked to stare at on object in the center of your line of vision (either the doctor's eyes, on a screen or using a computer program). As you are looking at the object, you will be asked to note when you see an object moving into your peripheral vision. This test is done to diagnose glaucoma or possible damage caused by a stroke.
Reviewed by the doctors at The Cleveland Clinic Cole Eye Institute.
Edited by Charlotte E. Grayson, MD, WebMD, October 2004.
Portions of this page © The Cleveland Clinic 2000-2005
Last Editorial Review: 6/29/2005