Periodic eye and vision examinations are an important part of preventive health care. Many eye and vision problems have no obvious signs or symptoms. As a result, individuals are often unaware that problems exist. Early diagnosis and treatment of eye and vision problems are important for maintaining good vision and eye health, and when possible, preventing vision loss.
Comprehensive eye examinations can take an hour or more, depending on the doctor and the number and complexity of tests required to fully evaluate your vision and the health of your eyes.
A comprehensive adult eye and vision examination may include, but is not limited to, the following tests. Individual patient signs and symptoms, along with the professional judgment of the doctor, may significantly influence the testing done
A patient history helps to determine any symptoms the individual is experiencing, when they began, the presence of any general health problems, medications taken and occupational or environmental conditions that may be affecting vision. The doctor or his technician will ask about any eye or vision problems you may be having and about your overall health. You will also be asked about any previous eye or health conditions for you as well as your family members.
Your eye doctor may use an auto-refractor to automatically determine your prescription. With this device a chin rest stabilizes your head while you typically look at a pinpoint of light or other image.
An auto-refractor, like a manual refraction, determines the lens power required to accurately focus light on your retina. Auto-refractors are especially useful in certain cases such as evaluating young children who may not sit still, pay attention or interact with the eye doctor adequately for an accurate manual refraction.
Studies have shown that modern auto-refractors are very accurate. They also save time. The auto-refraction takes only a few seconds, and the results obtained from the automated test greatly reduce the time required for your eye doctor to perform a manual refraction and determine your eyeglass prescription.
Visual Acuity Tests
Among the first tests performed in a comprehensive eye exam are visual acuity tests that measure 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.
Color Blindness Test
A screening test that checks your color vision often is performed early in a comprehensive eye exam to rule out color blindness. In addition to detecting hereditary color vision deficiencies, color blindness tests can also alert your eye doctor to possible eye health problems that may affect your color vision.
This is the test that your eye doctor uses to determine your exact eyeglass prescription.
During a refraction, the doctor puts the instrument called a phoroptor 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 looks clearer.
Based on your answers, your eye doctor will continue to fine-tune the lens power until reaching a final eyeglass prescription. The refraction determines your level of hyperopia (farsightedness), myopia (nearsightedness), astigmatism and presbyopia.
The slit lamp is an instrument that the eye doctor uses to examine the health of your eyes. The slit lamp, also called a biomicroscope, allows your eye doctor to get a highly magnified view of the structures of your eye to thoroughly evaluate your eye health and detect any signs of infection or disease.
During this test, your doctor will have you place your chin on the chin rest of the slit lamp and will then shine the lamp’s light at your eye. The doctor looks through a set of oculars (much like a microscope in a science lab) and examines each part of your eye in turn.
The doctor will first examine the structures of the front of your eye (lids, cornea, conjunctiva, iris, etc.). Then, with the help of a special high-powered lens, your doctor will view the inside of your eye (retina, optic nerve, macula and more).
A wide range of eye conditions and diseases can be detected with slit-lamp examination, including cataracts, macular degeneration, corneal ulcers, diabetic retinopathy, etc.
Applanation Tonometry (Glaucoma Test)
Glaucoma tests have several variations, all designed to measure the pressure inside your eyes. A common glaucoma test is the “puff-of-air” test, technically known as non-contact tonometry, or NCT. For NCT, the test begins with you putting your chin on the machine’s chin rest. While you look at a light inside the machine, the technician will puff a small burst of air at your open eye. It is completely painless, and the tonometer does not touch your eye.
Based on your eye’s resistance to the puff of air, the machine calculates your intraocular pressure (IOP). If you have high eye pressure, you may be at risk for or have glaucoma.
Another type of glaucoma test is performed with an instrument called an applanation tonometer. The most common of several versions of this instrument is mounted on the slit lamp.
For this test, your eye doctor will put yellow eye drops in your eye to numb it. Your eyes will feel slightly heavy when the drops start working. This is not a dilating drop — it is a numbing agent combined with a yellow dye that glows under a blue light. Then the doctor will have you stare straight ahead into the slit lamp while he or she gently touches the surface of your eye with the tonometer to measure your IOP.
Like NCT, applanation tonometry is painless. At most, you may feel the tonometer probe tickle your eyelashes. The whole test takes just a few seconds.
You typically have no warning signs of glaucoma until you already have significant vision loss. For this reason, routine eye exams that include tonometry are essential to rule out early signs of glaucoma and protect your eyesight.
A special camera takes a digital color photograph of the back of your eye. This test is recommended on a routine basis to provide your doctor with a baseline record of the appearance of your retina, internal blood vessels and optic nerve. It is also used to document diseases and anatomical abnormalities and monitor them over time.