Refraction is not an exam
A friend on social media recently tagged one of our office workers in a post. The author of the post was a mother in Alabama, whose child was diagnosed with a major eye disease that will probably (sadly) result in numerous future eye problems or blindness. The mother was upset that this eye disease was not caught early; after all, she took her child to the Wal-Mart eye doctor every couple of years. The child always read the letters correct on the letter mirror. But, the mother admitted, she never asked for dilation or further tests. “How was I supposed to know [what’s in an eye exam]?” she wrote angrily.
This post is not about the incompetence or languishing skills of commercial doctors. On the contrary, we know plenty of wonderful doctors who work at the Walmarts, Targets, and Costcos of the World.
This post is a reminder that health care is in the hands of the consumer. The quality of your time spent in the doctor’s chair is a reflection of the health care provider you choose.
At Premier Eyes, we believe in providing full scope eye health exams. This includes refraction and “reading the letters on the mirror,” but also goes further in screening for glaucoma and checking the back of the eye for signs of health problems.
The American Optometric Association gives great guidelines of what to expect from quality eye health exams. Below are some of the tests the AOA mentions.
Reading charts are often used to measure visual acuity.
Visual acuity measurements evaluate how clearly each eye is seeing. As part of the testing, you are asked to read letters on distance and near reading charts. The results of visual acuity testing are written as a fraction such as 20/40.
When testing distance vision, the top number in the fraction is the standard distance at which testing is done, twenty feet. The bottom number is the smallest letter size you were able to read. A person with 20/40 visual acuity would have to get within 20 feet of a letter that should be seen at 40 feet in order to see it clearly. Normal distance visual acuity is 20/20.
Preliminary testing may include evaluation of specific aspects of visual function and eye health such as depth perception, color vision, eye muscle movements, peripheral or side vision, and the way your pupils respond to light.
This test measures the curvature of the cornea, the clear outer surface of the eye, by focusing a circle of light on the cornea and measuring its reflection. This measurement is particularly critical in determining the proper fit for contact lenses.
Determining refractive error with a phoropter and retinoscope
Refraction is conducted to determine the appropriate lens power needed to compensate for any refractive error (nearsightedness, farsightedness, or astigmatism). Using an instrument called a phoropter, your optometrist places a series of lenses in front of your eyes and measures how they focus light using a hand held lighted instrument called a retinoscope. The doctor may choose to use an automated instrument that automatically evaluates the focusing power of the eye. The power is then refined by patient’s responses to determine the lenses that allow the clearest vision.
This testing may be done without the use of eye drops to determine how the eyes respond under normal seeing conditions. In some cases, such as for patients who can’t respond verbally or when some of the eyes focusing power may be hidden, eye drops are used. The drops temporarily keep the eyes from changing focus while testing is done.
Eye Health Evaluation
Tonometry measures eye pressure. Elevated pressure in the eye signals an increased risk for glaucoma.
External examination of the eye includes evaluation of the cornea, eyelids, conjunctiva and surrounding eye tissue using bright light and magnification.
Evaluation of the lens, retina and posterior section of the eye may be done through a dilated pupil to provide a better view of the internal structures of the eye.
Measurement of pressure within the eye (tonometry) is performed. Normal eye pressures range from 10 to 21 millimeters of mercury (mm Hg), averaging about 14 to 16 mm Hg. Anyone with eye pressure greater than 22 mm Hg is at an increased risk of developing glaucoma, although many people with normal pressure also develop glaucoma.
Additional testing may be needed based on the results of the previous tests to confirm or rule out possible problems, to clarify uncertain findings, or to provide a more in-depth assessment.