Near Point of Convergence: Measuring It Well and Its Limits

Updated 2026-10-22

Written by the Optics Trainer team from published research, with every source linked below.

The near point of convergence (NPC) is one of the simplest binocular vision tests and one of the most quoted. Yet published cut-offs range widely, the target and instrument change the result, and a single measurement can mislead. This guide covers how NPC is measured, where the commonly quoted values come from, how repeatable it is, and how to read it alongside the rest of the examination.

Break and recovery

NPC is usually recorded as two values: the break, when the patient reports diplopia or one eye is seen to deviate as the target approaches, and the recovery, when single vision returns as the target moves away. Recovery is generally more remote than break, as published values for children and adults show.

A 2022 review recommends recording three measurements, and CITT used the mean of three. Scheiman and colleagues describe repetition and a red glass as useful when other testing is equivocal. In 539 schoolchildren, Maples and Hoenes found NPC receded slightly over three consecutive trials, a change they did not consider clinically significant.

Target choice and instruments

The target matters, though studies disagree on how much. In children and young adults, Adler and colleagues found a penlight gave a more remote NPC than a pencil or fingertip, and the RAF rule's line target gave values about 1.9 times those with a fingertip. Siderov and colleagues found only small target effects, in the opposite direction for the RAF target in non-presbyopes, and none in presbyopes. Accommodative targets tend to give closer breaks than non-accommodative ones.

Methods are not interchangeable. In young adults, the RAF rule, a pencil and a red/green penlight method showed wide limits of agreement with each other. In presbyopes, using a penlight and watching the eyes is advised to help avoid confusing blur with diplopia. A polarised nonius method gave more remote breaks and higher sensitivity to symptoms but very low specificity in one study of 65 participants.

Published reference values and where they come from

Published cut-offs range from about 5 to 15 cm because of differences in target, age, instrument and authors. No single "normal" value applies to everyone:

Hayes and colleagues (1998) measured 297 schoolchildren who had passed a school vision screening, with an accommodative rule; at least 85% had a break of 6 cm or less, and they proposed a 6 cm clinical cut-off.
Maples and Hoenes (2007) studied 539 schoolchildren and proposed a break of 5 cm or less as a tentative benchmark.
Scheiman and colleagues (2003) studied 175 adults with normal binocular vision and proposed 5 cm for break and 7 cm for recovery, with an accommodative target or a penlight and red/green glasses.
The Convergence Insufficiency Treatment Trial (CITT) required a break of 6 cm or more as one of several entry criteria for convergence insufficiency in children aged 9 to 17, using the mean of three measurements.

How repeatable NPC is

Under a standard protocol, NPC is one of the more repeatable binocular vision measures. In 20 fifth- and sixth-graders, within-session and one-week reliability was good (intraclass correlations about 0.89 to 0.98). In 93 healthy adolescents aged 12 to 17, 90-day retest limits of agreement for NPC break were about ±2.5 cm, which gives a sense of how much change between visits may be noise.

NPC and convergence insufficiency

NPC alone does not diagnose convergence insufficiency. CITT combined a receded NPC with a larger exo deviation at near, reduced positive fusional vergence and symptoms. Definitions vary, and some do not require a receded NPC (Gantz and Stiebel-Kalish, 2022), so a receded NPC does not establish convergence insufficiency on its own, and a normal one does not always rule it out. Read NPC with the rest of the binocular vision assessment.

NPC in concussion screening

NPC distance is one of the components of the Vestibular/Ocular Motor Screening (VOMS) tool, developed in sport-related concussion research. In 462 collegiate athletes, 9.1% to 22.5% had a false-positive baseline VOMS depending on the interpretation criteria; these were symptom scores, not NPC alone. NPC is not a concussion test.

How Optics Tracker fits

Optics Tracker reports include left and right eye traces and disparity, and Optics Trainer VR includes vergence activities. Neither is presented as a replacement for a manual NPC measurement, and none of the studies above evaluated them.

Optics Tracker is clinical decision-support software. Its results support, and do not replace, clinical testing, professional diagnosis and clinical judgement.

Frequently asked questions

What is a normal near point of convergence?

There is no single value. Published cut-offs range from about 5 to 15 cm depending on the population, target and instrument; for example, 6 cm in one study of schoolchildren and 5 cm (break) and 7 cm (recovery) in a study of adults.

Does the target used for NPC matter?

It can. One study found a penlight or RAF rule line target gave a more remote NPC than a pencil or small letter, while another found only small effects. Use the same target each time and don't compare results across methods.

How many times should NPC be measured?

A 2022 review recommends recording three measurements, and CITT used the mean of three. Repetition is useful when other testing is equivocal.

Can NPC detect concussion?

NPC is not a concussion test. It is one component of the VOMS, a screening tool from sport-related concussion research, and baseline VOMS results can be positive in healthy athletes.