Visual Acuity
Is tested to see how clearly each eye can see. The results of this test are generally written as a fraction such as 20/40. The top number of the fraction is the standard distance of the test, twenty feet. The bottom number is the smallest letter size that can be read. This means that a person with 20/40 vision cannot read a letter that people with normal vision can read at 40 feet unless they are 20 feet away.
Refraction
Is used to choose the right lens power needed to correct nearsightedness, farsightedness, and astigmatism or for the use of multifocals (bifocals, trifocals or progressives). Using an instrument that contains a series of lenses, the optometrist measures how they focus light. After this process, the patient's responses to lens choices narrow down the right correction needed.
Dilation
Is the process of using eye drops to keep the pupil of the eye open, even in bright light. This process allows the optometrist to see all the way into the back of the eye, where the retina, optic nerve and important blood vessels are located. Not only are vision issues discovered during this process, but other general health issues such as hypertension may be noticed as well. |