Binocular Vision &

Eye Muscle Surgery Qtrly°

Major Review: hztennittent Exotropia; Basic and Divergence Excess Type

Summer of 1993 Volume 8 (No.3): 185-216

suppression patterns varied with the stimuli.

Awaya et al (85), using a phase difference haploscope, found that most patients with DEX(T) during exodeviation had two dense suppression scotomas, one corresponding to the fovea of the deviating eye and the other at the diplopia point. This dense suppression could be broken with a rapid oscillation technique revealing NRC diplopia.

Recently Melek et al (97) evaluated suppression and retinal correspondence in 21 X(T)s using a Goldman (bowl) Perimeter while the subjects viewed the fixation target with Bagolini Striated Glasses. Fixation and ocular position was monitored with frequent occlusion of the fixating eye. They reported that 52% of the manifest X(T)s had temporal suppression (10% demonstrated temporal suppression in the deviated eye; 10% temporal and nasal suppression in the deviated eye; and 24% temporal suppression in both eyes). The other 48% had suppression scotomas (38% had suppression of the diplopia point and a sector of the peripheral temporal retina, while the other 10% not only suppressed the diplopia point and temporal retina, but also the fovea). On the other hand, during normal alignment none of the X(T)s demonstrated suppression scotomas. Interestingly, none of their subjects demonstrated ARC with the Bagolini Striated Glasses during exodeviation.

These findings are in agreement with studies reported by Pratt-Johnson & Wee (96), Campos (88), Cooper & Feldman (86), and Cooper & Record (87) all whom reported a higher incidence of ARC and suppression with afterimage or anaglyph testing; and NRC with the Bagolini Striated Glasses.

Temporal hemiretinal suppression with NRC in the real world could not work. As seen in Figure 8, right, if the DEX(T) patient suppresses the temporal retina, while the nasal retina has NRC, the patient would not have altered egocentric localization of the objects seen by the deviated eye and severe visual confusion would ensue. Fortunately, DEX(T) patients do not report this phenomenon. If they did they would live in a very confused world.

(ARC):

ARC with X(T) was initially reported by Bielchowsky (8). He observed a patient who reported NRC on the afterimage test when the eyes were straight and harmon-

ions ARC when the eyes deviated (See Figure 9, next page). This duality of correspondence is unique to X(T). Burian (98) stated that suppression does not always occur during deviation in X(1):

“When the deviating eye turns out, there is a simultaneous displacement of the egocentric localization of all visual directions of the eye so that no diplopia occurs. This is anomalous retinal correspondence”. Other clinical reports of ARC come from Hugonnier (99), Burian

(98), Bagolini & Capabianco (100) and Chryssanthau (101). Campos (88), using Bagolini Striated Glasses with non-dissociating mirrors, found that most X(T)s demonstrate HARC. Campos & Cresi (89) reported that smaller angle X(T)s showed HARC without suppression, while larger angle X(T) often suppressed the diplopic image in the deviating eye. In their previously described Ganzfleld experiments Cooper & Feldman (86) reported that neither fovea suppressed during deviation.

Figure 8 (Cooper & Medow): Projection and spatial localization of targets on the horopter for a RX(T). The OS fixates a A with a + to the right while the OD fovea is lined up with a 0 and a [] to the right The distance from 0 to + equals the distance from 0 to [ ]. Cyclopean projection demnonstrates ARC and NRC projection respectfully. NRC would result in confusion, diplopia and inaccurate spatial localization which is rarely reported by XTs Functioning in the real world necessitates I-IARc.

197