Comprehensive eye exam each year is the best way to enjoy good vision throughout your life. 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.
Tests Used during Eye Examinations
There are many common tests your eye doctor uses during an eye examination. Some of these are listed below:
Vision Testing:
Vision testing involves making a person read standard sized letters at a specified distance. The doctors record the vision as a fraction e.g. 6/6 etc. The top number denotes the distance (in feet) at which the patient has been able to read the particular sized letter while the bottom number indicates the distance at which a normal person is expected to read the same letter. Near vision is tested separately in good illumination using special test charts held at normal reading distance. The testing is done with each eye separately. The doctors often test the vision using a pinhole. This gives an estimate of improvement possible with glasses. The patient in place of glasses cannot use the pinhole.
Refraction – This test uses an instrument referred to as a phoropter. It looks kind of like a space age eye examination machine with varying lenses. Your eye doctor will use this instrument to test various lenses against your eyes, enabling the eye doctor to determine the best power prescription for your eyeglasses or contacts. The phoropter measure the exact level of astigmatism, myopia or hyperopia you may have.
Tonometry – This test is important to determine the eye pressure in the evaluaton for glaucoma. There are various ways to test the intraocular pressure (IOP) or eye pressure. Non-Contact Tonometry is typically performed by the technician. Many of you know this test as the “puff of air test.” Contact Tonometry is performed by your eye doctor by a probe that touches the eye. But because a numbing drop is used during this test, you won’t feel a thing. Infact, most patients prefer this method over the puff of air.
Retinoscopy – This is a technique to obtain the objective measurement of your prescription. It provides a way to estimate what your vision prescription may be. It can either be performed by an automated machine or it can be done manually with a retinoscope. The retinoscope shines a bright light into the eye, while the doctor is observing the reflection off your retina, he or she can determine your estimated prescription.
Refraction – This test uses an instrument referred to as a phoropter. It looks kind of like a space age eye examination machine with varying lenses. Your eye doctor will use this instrument to test various lenses against your eyes, enabling the eye doctor to determine the best power prescription for your eyeglasses or contacts. The phoropter measure the exact level of astigmatism, myopia or hyperopia you may have.
Cover Test – During this test, your eye doctor will cover one eye at a time to detect any ocular deviation such as strabismus also known as an eye turn or lazy eye. Essentially, it measures how well your eye works together and helps detects problems including poor depth perception.
Slit Lamp – During this test the doctor uses a special high power microscope to examine the structures of your eye, testing for infections or ocular diseases. You place your chin on a chin rest, while your eye doctor reviews your ocular structures through the microscope. This test is beneficial for detecting conjunctivitis and other common eye diseases as well as more serious ocular conditions such as cataracts and macular degeneration.
Dilated Fundus Exam – This test requires the doctor place an eye drop in the eyes in order to dilate the pupil. With the pupils dilated, it creates a larger window for your doctor to look inside the eyes. The drops typically take 15-20 minutes to take effect. Once pupil dilated your doctor will test your eyes for various eye diseases. This is an important test for measure the health of the internal structures of the eye.
A-Scan – biometry by immersion has better reproducibility, which leads to an overall increase in accuracy. The immersion technique can be performed rapidly and with greater confidence than the applanation method. Making the change from the Applanation to immersion is well worth the small learning curve.
Visual Field Screening – This test is usually performed by the eye care assistant, also known as a technician, with the assistance of a machine to analyze your visual field. The machine then prints out a detailed reading of areas of the vision that were or were not seen.