How sensitive is pupil campimetry in hemifield loss?

BACKGROUND

The purpose of our study was to demonstrate the ability of pupil campimetry to reproduce visual field defects caused by pre-- and retrogeniculate lesions of the visual pathway.

METHODS

By means of infrared video pupillography, light responses to perimetric stimuli were recorded. The stimulus pattern consisted of 41 test spots of 4 degrees diameter and 140 cd/m(2) luminance distributed in the central (30 degrees ) visual field. Background luminance was 2.7 cd/m(2). Eight patients with pregeniculate lesions and eight patients with retrogeniculate lesions of the visual pathway were examined. Pupil field was evaulated by three skilled visual field interpreters masked to the patients' clinical data including conventional perimetry. The spatial concordance of the visual field and the pupil field was quantitatively assessed by the ratio of intersection area and union area of the observer's result and the visual field defect measured by conventional perimetry. The ratios in the two cohorts were compared by the Wilcoxon rank-sum test.

RESULTS

The concordance between pupil and conventional perimetry was better in the group of patients with retrogeniculate lesions. Ratios of the intersection area and the union area in this group were significantly higher than for the group with pregeniculate lesion of the visual pathway (p < 0.05).

CONCLUSIONS

According to our results, pupil campimetry demonstrates retrogeniculate visual pathway lesions well in contrast to pregeniculate lesions. This is in contradiction to the classical view of the pupillary pathways, where a retrogeniculate lesion actually should not influence pupillary function, whereas pregeniculate lesions should show pupillary scotomata. The cause might be that different components of the pupillary light reflex are being involved in pre-- and retrogeniculate lesions, and the stimulus characteristics of pupil perimetry address better the components represented in the retrogeniculate pathway.