What is Negative Relative Accommodation (NRA)?
Negative Relative Accommodation (NRA) is a clinical test that quantifies the amount of accommodation the eyes can relax while still maintaining a single, fused binocular image at near. Rather than isolating accommodation on its own, the test captures how the accommodative and vergence systems work together. NRA forms part of a wider binocular vision workup and is normally recorded together with positive relative accommodation (PRA).
How is Negative Relative Accommodation Measured?
The test is carried out binocularly at a fixed near distance of 40 cm, with the patient’s full refractive correction in place. Using a phoropter or trial frame, the examiner adds plus power in +0.25 D increments while the patient reads a near target, usually a line one size larger than the smallest print they can read comfortably.
Plus lenses continue to be added until the patient first reports sustained blur that they cannot clear. At this point, the cumulative plus power is noted as the NRA result, recorded in positive diopters (for instance, +2.00 D).
Because the test reflects the coupling between accommodation and vergence, it is always performed binocularly. NRA is generally taken immediately before or after the PRA measurement, as the two are assessed as a pair.
What is a Normal NRA Value?
For patients who are not yet presbyopic, the expected NRA range sits between +1.75 D and +2.50 D, averaging close to +2.00 D. Children tend to produce higher figures, consistent with their greater accommodative range.
Findings below +1.75 D fall into the reduced category. Findings above +2.50 D are also clinically significant and warrant further investigation.
What Do Abnormal NRA Results Indicate?
An NRA reading outside the expected range can point in one of two directions, each with its own clinical implications.
Reduced NRA (below +1.75 D)
When NRA is low, it shows the accommodative system is unable to relax accommodation fully while maintaining clear, single binocular vision. This pattern is associated with accommodative spasm or accommodative excess, where the ciliary muscle stays contracted and has trouble letting go. Symptoms patients may report include:
- Distance vision that stays blurred after extended near tasks
- Trouble bringing distance objects into focus after time spent on a screen or book
- Pseudomyopia, where sustained accommodative contraction creates a temporary appearance of short-sightedness
Elevated NRA (above +2.50 D)
When NRA is elevated, it often points to a distance prescription carrying more minus power than the patient requires. To see clearly, the patient maintains a higher level of accommodative effort, and that baseline effort increases the recorded NRA value.
An NRA that comes in higher than expected should trigger a second look at the distance refraction. Uncorrected or under-corrected hyperopia can also produce an elevated NRA.