Near Points of Convergence and Accommodation in a Population of University Students in Iran.

Hassan Hashemi,Mehdi Khabazkhoob,Abbasali Yekta,Amir Asharlous,Mojgan Pakbin,Babak Ali,Mohammadreza Aghamirsalim,Hadi Ostadimoghaddam

doi:10.18502/jovr.v14i3.4787

Abstract

PurposeTo determine the distribution of the near point of convergence (NPC) and near point of accommodation (NPA) in a young student population in Iran.MethodsThe subjects were selected using a cluster sampling method. All students underwent optometry tests, including visual acuity measurement, refraction, and cover test, as well as ophthalmic examinations. The NPC and NPA were measured using an accommodative target (near Snellen chart).ResultsOf 1,595 students, the data of 1,357 were analyzed. The mean NPC and NPA in the total sample were 7.25 cm (95% confidence interval [CI], 7.02 to 7.48) and 9.99 cm (95% CI, 9.69 to 10.29), respectively. Older age was associated with an increase in the NPC, which increased from 6.98 cm in 18–20 years olds to 9.51 cm in those over 30 years. The NPA was significantly associated with age and refractive errors in the multiple linear regression model, increasing from 9.92 cm in 18–20 years olds to 11.44 cm in those over 30 years ( = 0.003). Hyperopic eyes had lower NPA than myopic and emmetropic eyes ( = 0.001). In younger age groups, the mean accommodation amplitude was lower than the mean Hofstetter value. Moreover, with age, especially after 30 years, the mean values surpassed those determined using the Hofstetter formula.ConclusionThe NPC values in this study were lower than those previously reported for identical age groups. The Hofstetter formula is not always an accurate predictor of the accommodation amplitude in the Iranian adult population.

Highlights

Non-strabismic vergence dysfunctions and accommodation anomalies are the main causes of symptoms such as occasional double vision, headaches, and blurred vision after prolonged near work.[1,2,3] Students experience such symptoms more often than others do because of their higher demand for near vision, and this can affect their academic activities.[1]
The findings of the present study showed that the mean near point of convergence (NPC) for all the students was 7.25
The mean NPC in the emmetropic, myopic, and hyperopic groups was 7.29, 7.21, and 7.16 cm, respectively, without any significant differences between the three groups in terms of the NPC (P = 0.322)

Summary

Introduction

Non-strabismic vergence dysfunctions and accommodation anomalies are the main causes of symptoms such as occasional double vision, headaches, and blurred vision after prolonged near work.[1,2,3] Students experience such symptoms more often than others do because of their higher demand for near vision, and this can affect their academic activities.[1]. Many studies have shown that the NPC increases with age,[12,13,14,15] and some indicate that the NPC is higher in men than in women,[15] but its relationship with sex remains unclear

Methods

Results

Conclusion