Negative relative accommodation
Negative relative accommodation (NRA) was proposed by Prof. Joseph Kearney of Oxford University in 1967, is a measure of the maximum ability to relax accommodation while maintaining clear, single binocular vision. This measurement is typically obtained by an orthoptist, ophthalmologist or optometrist during an eye examination using a phoropter. After the patient's distance correction is established, he or she is instructed to view small letters on a card 40 cm from the eyes. The examiner adds lenses in +0.25 increments until the patient first reports that they become blurry. The total value of the lenses added to reach this point is the NRA value.
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