Thursday, September 5, 2013

A prospective study of different test targets for the near point of convergence

A prospective study of different test targets for the near point of convergence

Purpose: To determine whether different test targets including an accommodative target (AT), a
transilluminator (TR), and a transilluminator with a red lens (RL), affect the near point of convergence
(NPC) value; and to determine which test target is most sensitive to identify convergence
insufficiency (CI) in young adults.

Methods: Subjects were 36 optometry students from the Illinois College of Optometry, including 18
subjects with normal binocular vision (control group) and 18 subjects with CI. None of the subjects
had accommodative insufficiency. The NPC break and recovery were measured by three methods:
AT, TR, and RL. Each test method was administered by a different examiner and the test sequence
was randomized.

Results: The mean NPC break values for AT, TR, and RL in the control group were 4.31, 3.76, and
4.08 cm respectively, compared to 10.05, 11.37 and 13.04 cm in the CI group. The mean recovery
values were 6.23, 5.56, and 5.95 cm for AT, TR, and RL respectively in the control group, vs 12.21,
14.37, 16.40 cm in the CI group. Significant differences in NPC break and recovery values were
detected in the CI group between RL and AT, but not between AT and TR, or TR and RL. There was
no significant difference in NPC values using the three targets in the control group. For an NPC cut
point of 6 cm (break) and 9 cm (recovery), RL had higher sensitivity (100%) and specificity (88.9%)
as well as lower false positive (10%) and false negative (0%) values compared to AT.

Conclusion: NPC with RL is a more sensitive method to identify abnormal findings and assist in diagnosing CI compared to using AT or TR. We recommend that NPC with RL be routinely used to evaluate patients suspected of having CI.

Comments: Since convergence insufficiency is frequently encountered in all age groups and can significantly detract from ones quality of life, the NPC test with a red lens as noted above should be a routine, standard part of any comprehensive eye and vision examination. If you would like a copy of the original article click on the title above. DM

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