When you think of a routine eye exam, this test is probably what you
picture. Your doctor will ask you to read a series of letters off of a Snellen
eye chart posted 20 feet away from you. This test allows him or her to
detect any significant changes in your vision.
If you have already been diagnosed with cataracts, and your vision has degenerated to 20/40 or below, your doctor may recommend surgery. In some cases, you may have a good score on this test, but you still present with other cataract symptoms, such as light sensitivity or blurred vision. When this occurs, your ophthalmologist will likely recommend more tests to determine whether cataracts are, in fact, responsible for your symptoms.
Your doctor will give you eye drops to dilate your pupil. By shining a light
on the front of your eye, he or she can usually detect any white spots on
your lens, even if they are very minute. The slit lamp exam often allows
for extremely early diagnosis, so that your ophthalmologist can detect
cataracts before they begin to affect your vision. During the test, your
doctor will likely use a magnifying lens to examine your retina and optic
nerve. Although this step is not necessary for cataracts detection, it
enables your doctor to check for other serious eye conditions.
During a glare test, you will be asked to read the Snellen chart under
various lighting conditions. If you have difficulty discerning the letters
under very bright light, this could be a good indication of cataracts.
Named after its designer, Dr. Shinobu Ishihara, this test uses a series of
plates covered with colored dots. The dots vary in color, forming a
number in the center of the plate. Those with an inability to distinguish
hues on the blue-green end of the spectrum will not be able to see the
numbers. If you have not been previously diagnosed as color blind, and
you do not pass the Ishihara color test, you may be suffering from
advanced cataracts.
Your ophthalmologist will direct a puff of air towards your eye, and it will
measure the intraocular pressure (IOP), determined by the amount of
vitreous fluid inside your eye. Although tonometry tests are most
commonly used to diagnose glaucoma, it is important that your doctor be
as thorough as possible during cataract diagnosis. When left undiagnosed
and untreated, glaucoma, macular degeneration, and similar eye diseases
can have dramatic consequences for your vision and ocular health.
