Positive relative accommodation

Positive relative accommodation

Positive relative accommodation (PRA) is a measure of the maximum ability to stimulate accommodation while maintaining clear, single binocular vision [http://www.vision-therapy.com/Glossary_of_Terms.htm] . This measurement is typically obtained by an 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 PRA value.

High PRA values (> or = 3.50 diopters) are considered to be diagnostic of disorders involving accommodative excessGarcia A, Cacho P, Lara F. "Evaluating relative accommodations in general binocular dysfunctions." "Optom Vis Sci." 2002 Dec;79(12):779-87. PMID 12512686.] . Those with accommodative insufficiency typically have PRA values below -1.50 diopters [http://www.aoa.org/documents/CPG-18.pdf] .

References

ee also

*Amplitude of accommodation
*Convergence insufficiency
*Negative relative accommodation


Wikimedia Foundation. 2010.

Игры ⚽ Поможем решить контрольную работу

Look at other dictionaries:

  • 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.[1] This measurement is typically obtained by an orthoptist,… …   Wikipedia

  • Accommodation (eye) — Accommodation is the process by which the increases optical power to maintain a clear image (focus) on an object as it draws near the eye. The young human eye can change focus from distance to 7 cm from the eye in 350 milliseconds. This dramatic… …   Wikipedia

  • Relative — can refer to: *Kinship, the principle binding the most basic social units society. If two people are connected by circumstances of birth, they are said to be relatives Physics*Relativity as a concept in physics (for example Albert Einstein s… …   Wikipedia

  • Amplitude of accommodation — (AA) is a measurement of the eye’s ability to focus clearly on objects at near distances (i.e. accommodation). This eye focusing range for a child is usually about 5 ndash;7.5 cm (2 ndash;3 inches). For a young adult, it is 10 ndash;15 cm (4… …   Wikipedia

  • Accommodation — In medicine, the ability of the eye to change its focus from distant to near objects (and vice versa). This process is achieved by the lens changing its shape. Accommodation is the adjustment of the optics of the eye to keep an object in focus on …   Medical dictionary

  • Contingency theory of accommodation — The contingency theory of accommodation was proposed in 1997 by Amanda Cancel, Glen Cameron, Lynne Sallot and Michel Mitrook to highlight the pertinent factors of how a public relations practitioner facilitates communication between the… …   Wikipedia

  • Eyeglass prescription — Using a phoropter to determine a prescription for eyeglasses An eyeglass prescription is an order written by an eyewear prescriber, such as an optometrist or ophthalmologist, that specifies the value of all parameters the prescriber has deemed… …   Wikipedia

  • Eye examination — An eye examination is a battery of tests performed by an optometrist or ophthalmologist assessing vision and ability to focus on and discern objects, as well as other tests and examinations pertaining to the eyes.All people should have periodic… …   Wikipedia

  • Convergence insufficiency — Convergence Insufficency Classification and external resources ICD 10 H51.1 ICD 9 378.83 …   Wikipedia

  • Prism (optics) — For other uses, see Prism (disambiguation). A plastic prism In optics, a prism is a transparent optical element with flat, polished surfaces that refract light. The exact angles between the surfaces depend on the application. The traditional… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”