standard deviation of the differences by 1.96. The coefficients of repeatability for the VG test were 6.6 for no elevation or depression of gaze and 6.2 for downgaze. The respective coefficients of repeatability for the MT test were 2.8 and 3.6 (Table 1).

Table 1. Means (and standard deviations in parentheses) for both examiners and the coefficients of repeatability for each of the tests. Units are prism diopters. VG, von Graefe test; MT, modified Thorington test; S, straightforward position; D, downgaze

Discussion

The results of the present study agree with previous studies [1-5] in finding better repeatability with the MT test than the VG test. This better repeatability is present under a variety of test conditions, including with or without the phoropter and in downgaze as well as with no vertical gaze deviation from straightforward position.

The VG test is the most commonly used subjective dissociated phoria in optometric practice. Some clinicians have observed that the MT test is generally simpler than the VG test in terms of instrumentation and patient instructions. [2,6] The fact that the MT also offers better repeatability than the VG suggests that its more widespread adoption as a routine phoria test may be advisable.

Repeatability of other less commonly used phoria tests has also been studied. One investigation reported the repeatability of the VG test to be better than that for the Maddox rod test. [1] Another study found repeatability for the near Howell card phoria to be better than that for the VG test and nearly as good as that for the MT test. [3]

The means found in the present study are similar to previous studies comparing VG and MT tests, in which means for the VG ranged from -2.2 to - 5.0 and means for the MT ranged from -2.1 to -3.4 . [2,3,5-7] In the present study, as in the previous studies, standard deviations for the VG were higher than for the MT. It has been reported that for midrange phorias, there is quite good

Chapter 8

TEMPORARILY BLIND IN ONE EYE:

EMOTIONAL PICTURES PREDOMINATE

IN BINOCULAR RIVALRY

Georg W. Alpers1 and Antje B.M. Gerdes

University of Würzburg and University of Bielefeld, Germany

Abstract

Preferential perception of emotional cues may help an individual to respond quickly and effectively to relevant events. Existing data supports this hypothesis by demonstrating that emotional cues are more quickly detected among neutral distractors. Little data is available to demonstrate that emotional stimuli are also preferentially processed during prolonged viewing. The preferential perception of visual emotional cues is apparent under conditions where different cues compete for perceptual dominance. When two incompatible pictures are presented to one eye each, this results in a perceptual alternation between the pictures, such that only one picture is visible while the other is suppressed. This so called binocular rivalry involves different stages of early visual processing and is thought to be relatively independent from intentional control. Several studies from our laboratory showed that emotional stimuli predominate over neutral stimuli in binocular rivalry. These findings can be interpreted as evidence for preferential processing of emotional cues within the visual system, which extends beyond

1E-mail address: alpers@psychologie.uni-wuerzburg.de. Address for correspondence: PD Dr. Georg W. Alpers Department of Psychology, (Biological Psychology, Clinical Psychology, and Psychotherapy), University of Würzburg, Marcusstraße 9-11 , D- 97070 Würzburg, Germany, Tel.: 0049-931-31-2840, Fax: 0049-931-31-2733.