Target-Dependent Variability in Near Point of Convergence Measurements: A Repeated-Measures Study

Doi: 10.36351/pjo.v42i3.2409

Abstract

Purpose:  To determine the test difference between the Near Point of Convergence (NPC) break and recovery distance depending upon accommodative fixation target and non-accommodative fixation target and the degree of difference that could be ascribed to the measurement method in healthy young adults that have normal binocular vision.

Study Design:  A Repeated-Measures Study.

Place and Duration of Study:  Teerthanker Mahaveer University, India from January 2025 to December 2025.

Methods:  The study involved 130 subjects (20-26 years of age) with normal vision. RAF ruler and pencil scale push up(accommodative target) and NPC with red-filter torchlight (non-accommodative target)methodswere used for NPC break and recovery. Measurements were taken under ordinary conditions by one examiner. Descriptive statistics, ANOVA and Bonferonni adjusted post-hoc analysis were used.

Results:  The three methods were found to be statistically significant in the NPC break and recovery distances (p < 0.001). The accommodation targets were much closer to NPC than the non-accommodative. The RAF ruler provided the least distance of break and recovery and was followed by the pencil push-up method and then finally, the NPC with red-filter torch-light method provided the most receded values. The size of the effect was significant that indicated that the level of influence of target type on NPC outcomes was high.

Conclusion:  Accommodative and non-accommodative NPC are exhaustive of each other and NPC is a clinic-dependent strategy. NPC assessment techniques should also be used and reported consistently to achieve proper clinical interpretation and comparability of the results in research.