An enhancement to the Maddox Wing test for the reliable measurement of horizontal heterophoria

Abstract

Purpose: To attempt to improve the reliability of the Maddox Wing (MW) test for the measurement of horizontal heterophoria at near.

Methods: Horizontal heterophoria measurements at 30 cm using the MW instrument were made on a group of 58 normally-sighted binocular young adult subjects. The procedures were repeated at each of five weekly visits. The standard tangent scale card provided by the instrument's manufacturer was used as the control condition vs four alternative cards designed to enhance accommodative stimulation and improve operational reliability.

Results: A statistically-similar mean near phoria value was recorded using each of the five cards. However one of the alternative card designs produced a small but statistically significantly less variable result than the others: this design featured a much smaller typeface (4pt) than that used for the digits on the standard card, and the horizontal row of numbers was flanked by two periods of a low spatial frequency (< 2 c deg(-1)) square wave grating.

Conclusions: It is suggested that for improved reliability of near phoria measurement when using the MW instrument a more appropriately detailed design of tangent card would promote enhanced accommodation, an operational consideration likely to be especially relevant when examining children.