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Positive relative accommodation (PRA) in biology, is a measure of the maximum ability to stimulate eye accommodation while maintaining clear, single binocular vision.cite-ref-1[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, she or he is instructed to view small letters on a card 40 cm from the eyes. The examiner adds lenses in −0.25 diopter increments until the patient first reports that they become blurry. The total value of the lenses added to reach this point is the PRA value.

High PRA values (>= 3.50 diopters) are considered to be diagnostic of disorders involving accommodative excess.cite-ref-garcia-2-0[2] Those with accommodative insufficiency typically have PRA values below −1.50 diopters.cite-ref-3[3]

• See also

• References

• Accommodation in fish

• Adaptation (eye)

• Amplitude of accommodation

• Convergence insufficiency

• Mandelbaum effect

• Negative relative accommodation

cite-note-11. ↑ www.vision-therapy.com Archived December 8, 2005, at the Wayback Machine

cite-note-garcia-22. ↑ citerefgarciacacholara2002Garcia A, Cacho P, Lara F (Dec 2002). "Evaluating relative accommodations in general binocular dysfunctions". Optom. Vis. Sci. 79 (12): 779–87. doi:10.1097/00006324-200212000-00010. hdl:10045/9622. PMID 12512686. S2CID 31075351.

cite-note-33. ↑ "Care of the Patient with Accommodative and Vergence Dysfunction" (PDF). Archived from the original (PDF) on May 10, 2006. Retrieved May 8, 2006.