Modified Thorington Test for Near Heterophoria

The push-button LED lighted Slant Modified Thorington card (Richmond Products Inc., Albuquerque, NM) was used. The red Maddox rod was slotted over the right eye for testing. The red Maddox rod was oriented horizontally and vertically, respectively, in the trial frame for near lateral and vertical phoria testing. The Slant Modified Thorington card was positioned at 40 cm, and participants were instructed to look at the light in the center of the card and to tell the examiner the location of the streak relative to the light. To determine the size of the phoria, the participant was asked to report the target closest to which the streak passed. If the vertical streak passed through the spot of light, orthophoria was recorded through a number (esophoria) and a letter (exophoria). In vertical phoria testing, a right hypophoria and a right hyperphoria were recorded with the corresponding magnitude if the horizontal streak passed through a number and a letter, respectively.