Refraction

The refractive examination is how the doctor determines a glasses prescription. It is the process by which the doctor determines what lenses help you achieve your best visual acuity. Your "visual acuity" refers to the clarity of your central vision - how well you see objects in your direct line of sight. Your acuity can be affected by both internal and external conditions.

During the examination process, the doctor is testing your ability to recognize symbols (such as letters on an eye chart). Most often a phoropter is used to demonstrate different powers of lenses for you. The phoropter is the instrument you look through as the doctor asks you, “Which lens is better, one or two?” Your responses help guide the doctor in determining your refractive error and which lenses are necessary, if any, to bring you to your best acuity. An eyeglass or contact lens prescription includes the powers required to give you your best vision.

It is important to understand that 20/20 vision is not always achievable through the use of lenses. There are many diseases and conditions of the eye that might prevent clear vision with glasses. During the course of an examination your eye doctor may look for some of these problems to explain your decreased vision.

*The information provided by this Web site is for educational purposes only. This Web site is not comprehensive on the topics addressed. It is not a substitute for direct consultation with your health care provider. Always consult a licensed professional regarding your specific condition. Any trademarks referred to are the property of their respective owners.