Developing age-reference values for convergence and visual attention assessments

Definitions and cutoff values for impaired near point of convergence, and for dominant/non-dominant hand completion of line bisection and cancellation tasks, in older adults are lacking. In this study, we investigate the measurements, response times, and accuracy in a non-clinical population with healthy eyes and cognition.

This was a prospective cross-sectional study recruiting adults older than 50 years. Demographic data included hand dominance, sex, age, and ethnicity. The average of three near point of convergence measurements was recorded. Accuracy and speed of task completion were recorded for two-line bisection tasks (3 lines and 10 lines) and for the clock cancellation task, using dominant and non-dominant hands.

A total of 240 participants (161 female), with mean age of 61.23 years (SD8.71, range 50-97) were recruited. All participants had best corrected visual acuity of better than 0.1logMAR in each eye with no ocular pathology, and with no neurological disease. Overall mean near point of convergence was 9.22 cm (SD4.13), with slight decrease in convergence with increasing age (mean 11.71 cm in the 80th decade). Error cutoff for line bisection was determined as 6 mm with greater accuracy for the 10-line vs 3-line task. Error cutoff for the clock cancellation task was 42 with mean completion time of 1.5 minutes.

We report normative ranges of older adults ( >50 years) to which future clinical comparisons can be made when evaluating near point of convergence and visual inattention. Further research is required in acquired brain injury populations to take into consideration any additional impact on task completion due to co-morbidities/associated sequelae of the brain injury.