Negative relative accommodation
Negative relative accommodation (NRA) was proposed by Joseph Kearney of Oxford University in 1967 as a measure of the maximum ability to relax accommodation while maintaining clear, single binocular vision. It is an indirect measurement of fusional vergence in binocular vision.[1]
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, the patient is instructed to view small letters on a card 40 cm from the eyes. The examiner adds convex lenses in +0.25 increments until the patient first reports that they become blurry.[2] The total value of the lenses added to reach this point is the NRA value. High NRA values (above +2.50) might be evidence to over minus, uncorrected hyperopia or latent hyperopia.[citation needed]
See also
[edit]References
[edit]- ↑ Scheiman, Mitchell; Wick, Bruce (2008). Clinical Management of Binocular Vision: Heterophoric, Accommodative, and Eye Movement Disorders. Lippincott Williams & Wilkins. p. 4. ISBN 978-0-7817-7784-1.
- ↑ Millodot, Michel (2017-10-19). Dictionary of Optometry and Vision Science. Elsevier Health Sciences. p. 7. ISBN 978-0-7020-7223-9.