According to the Centers for Disease Control and Prevention (CDC), approximately 12 million Americans over the age of 40 have some kind of visual impairment. These days, there are many different types of test an ophthalmologist or optometrist can perform to determine whether a person is suffering from a disorder in one or both eyes. Continue reading to learn more about a few of these tests and how eye problems are diagnosed.
Angiography
In fluorescein angiography, a doctor injects a fluorescent dye—which is visible in blue light—into the patient’s arm. As the dye circulates up into the eye, the doctor takes photographs of the retina, choroid, optic disc and iris. Fluorescein angiography can help diagnose macular degeneration, blocked blood vessels and diabetic retinopathy.
Indocyanine green angiography is similar to fluorescein angiography, but the test allows doctors to get a better look at the blood vessels in the choroid. It’s often used to show macular degeneration and detect the development of new blood vessels.
Electroretinography
This test allows doctors to exam the function of the retina’s light-sensing photoreceptors by measuring the retina’s response to flashing lights. In the test, the patient is placed in a dark room and subjected to a flashing light. Electrodes placed on the cornea and patient’s face record the retina’s response to the light throughout the test. Electroretinography can evaluate diseases affecting photoreceptors, like retinitis pigmentosa.
Ultrasonography
Common types of eye tests also include ultrasonography. In this exam, a probe is placed on the patient’s closed eyelid that bounces sound waves off the eyeball. The reflected waves generate a two-dimensional image of the eye. This test can be used to identify abnormal structures like tumors or retinal detachment. A doctor can also use ultrasonography to determine the thickness of the cornea or examine blood vessels.
Pachymetry
Before performing a refractive eye surgery like LASIK, a doctor must perform pachymetry to measure the thickness of the patient’s cornea. This test is usually performed using ultrasonography, where the eye is numbed with eyedrops, and an ultrasound probe is placed directly on the cornea. This test is completely safe, and the patient doesn’t feel a thing.
Optical coherence tomography (OCT)
Doctors will use OCT to analyze issues with the retina, like macular degeneration. OCT can also be used for glaucoma or other disorders that cause new blood vessel formation. OCT is similar to ultrasonography, but it uses light instead of soundwaves to identify swelling of the retina.