What a thorough eye test will cover
A comprehensive eye exam contains several tests, from simple eye chart reading to tiny structure visualization. Some factors play a role in deciding the exam time, such as caseload and test complexity. In this article, a couple of simple and complex eye tests are introduced in detail.
Retinoscopy determines approximate prescription
Retinoscopy is always used to get an approximation of the patient’s prescription. The patient will be required to fixate on a large target and receive a light shined by the doctor. By changing lenses in front of the eyes and interpret the light reflects from the eyes, the doctor can work out the general prescription.
Refraction test determines precise prescription
Precise prescription can be determined by a refraction test, which uses a phoropter to switch lenses with different refractive powers. From the patient’s vision response to these lenses, the doctor can determine the final exact prescription for farsightedness, nearsightedness, astigmatism or presbyopia.
Cover test for amblyopia detection
Amblyopia is a popular ocular disorder among immature infants and little kids. Today, there is a simple and common eye test named cover test that is used to search out the potential risks or early signs of amblyopia, such as strabismus and turned eye. This test requires the patient to focus on a distant object and alternately cover one of the eyes. The doctor can get useful information by observing the way the eye moves.
Visual field test for detecting blind spots
In addition, a visual field test is widely used to screen the patient’s peripheral vision to find the presence of blind spots, which may be caused by glaucoma. Following that, stroke or tumor-caused brain damage can be located by analyzing the discovered blind spots.
Wavefront aberrometer can detect higher-order visual aberrations
An autorefractor or aberrometer with wavefront technology can be used to evaluate the way in which the retina refracts light rays, and then the patient’s wavefront map can be formulated. This test is convenient since it only requires people to rest their chin on the machine. This test can detect high-order aberrations that are beyond the above two tests, which can only diagnose simple conditions.
Slit lamp test can detect many eye diseases
The slit lamp test also uses a chin rest to stabilize the patient and shines its light at him. The doctor looks through a set of lenses to get the highly magnified images of the patient’s eye lids, cornea, conjunctiva and iris, in order to find any sign of eye infection or disease. With a high-powered lens, more complex eye diseases such as cataracts, macular degeneration, corneal ulcers and diabetic eye disease can be detected, by viewing the retina, optic nerve and macula.
Two glaucoma tests for measuring intraocular pressure
Today, glaucoma tests can be used to measure the eye’s intraocular pressure. By puffing an air burst at an open eye and evaluate its resistance, the commonly used non-contact tonometer can calculate the eye intraocular pressure. The process is painless and the patient just needs to rest his or her chin. Another machine used to measure the intraocular pressure is an applanation tonometer, which is always mounted on the slit lamp. Numbed by a yellow drop, each of the eyes will be touched by a bright-blue glowing instrument, which manually measures the intraocular pressure. Unlike non-contact tonometry, applanation tonometry may bring probe tickle on the eyelashes. Glaucoma tests are important for long-term eye health.
View eye structure using dilating drops
For better viewing of the inside structure, the doctor may put dilating drops of different strength in the eyes. After 20 to 30 minutes, the drops will widen the pupils and make the eyes sensitive to light. Within the following hours, the doctor can use instruments and light sources to examine the eye’s internal components, in order to discover potential eye diseases. After such a test, the patient needs a pair of sunglasses to protect the weak eyes from sun light on the way home.
Some other tests
Besides the above common tests, contact lenses evaluation, LASIK work-ups and pediatric exams can be additional items, depending on personal needs. For precise results, it is a must to strictly follow the doctor’s instructions during all test items.