Chromatic pupillography in hemianopia patients with homonymous visual field defects

• Published in: Graefe's archive for clinical and experimental ophthalmology Vol. 255; no. 9; pp. 1837 - 1842
• Main Authors: Maeda, Fumiatsu, Kelbsch, Carina, Straßer, Torsten, Skorkovská, Karolína, Peters, Tobias, Wilhelm, Barbara, Wilhelm, Helmut
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.09.2017; Springer Nature B.V
• Subjects: Cornea; Illumination; Latency; Medicine; Medicine & Public Health; Neurophthalmology; Occipital lobe; Ophthalmology; Retina; Retinal ganglion cells; Sensory neurons; Vision; Visual cortex; Visual field; Dorsal midbrain; Pupillary hemihypokinesia; Pupil light reflex; Visual cortex; Intrinsically photosensitive retinal ganglion cells; Homonymous hemianopia
• ISSN: 0721-832X; 1435-702X
• DOI: 10.1007/s00417-017-3721-y

Purpose The pupil light reflex is considered to be a simple subcortical reflex. However, many studies have proven that patients with isolated occipital lesions with homonymous hemianopia show pupillary hemihypokinesia. Our hypothesis is that the afferent pupillary system consists of two pathways: one via intrinsically photosensitive retinal ganglion cells (ipRGCs), the other running through the normal RGCs via the visual cortex. The purpose of this study was to test the hypothesis of these two separate pupillomotor pathways. Methods 12 patients (59.1 ± 18.8 years) with homonymous hemianopia due to post-geniculate lesions of the visual pathway and 20 normal controls (58.6 ± 12.9 years) were examined using chromatic pupillography: stimulus intensity was 28 lx corneal illumination, stimulus duration was 4.0 s, and the stimulus wavelengths were 420 ± 20 nm (blue) and 605 ± 20 nm (red), respectively. The examined parameters were baseline pupil diameter, latency, and relative amplitudes (absolute amplitudes compared to baseline), measured at maximal constriction, at 3 s after stimulus onset, at stimulus offset, and at 3 s and 7 s after stimulus offset. Results The relative amplitudes for the red stimulus were significantly smaller for hemianopia patients compared to the normal controls [maximal constriction: 35.6 ± 5.9% (hemianopia) to 42.3 ± 5.7% (normal); p  = 0.004; 3 s after stimulus onset: p  = 0.004; stimulus offset: p  = 0.001]. No significant differences in any parameter were found between the two groups using the blue stimulus. Conclusions The results support the hypothesis that the ipRGC pathway is mainly subcortical, whereas a second, non-ipRGC pathway via the occipital cortex exists.