An optometer is a device that measures the path that
light takes when it enters the eye. This is known as eye
refraction. If there is an error in the way light travels
through the eye, it is known as a refractive error, which
may need correction through eyeglasses or contact
lenses. The use of an optometer helps generate
numbers that measure the range and power of a
personís vision. 
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These numbers are recorded in the patientís chart and are used to help monitor the
status of the patientís vision. Optometers help select the type of eyeglass prescription
someone needs. The use of an optometer is called optometry and they are used by two
types of eye doctors known as optometrists and ophthalmologists. Any eye care
professional should be able to read the numbers generated from optometers.

The term optometer can also be used in a more general sense to describe any device
that measures light and the bending of light. These types of optometers can be used in
laboratories, for example, to measure the degree to which light emissions from a lamp
meets safety guidelines.

Optometer comes from the Greek word "optikos" meaning "sight," and the Greek word
"metron" meaning "measure." Put the two words together and you have "measure sight."
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