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Helmut Wilhelm, Fumiatsu Maeda, Tobias Peters, Barbara Wilhelm, Pupil Research group, Centre for Ophthalmology, University of Tuebingen; Do Intrinsic Photosentive Ganglion Cells (ipRGC) Really Project to the Dorsal Midbrain? Color Pupillography in Patients with Pretectal Lesions. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4111.
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Patients with a lesion of the dorsal midbrain usually show the following findings: 1. Bilaterally absent pupillary light reaction 2. Preserved near response 3. Upgaze palsy (most pronounced for saccades) 4. Preserved vestibular ocular reflex Actually, the pupillary light response is not completely absent. Using a strong light, the pupil constricts slowly. It could be shown that pupillary responses to gratings and colour patterns were the same as in normal subjects.
We had the possibility to examine 4 patients with a profound lesion of the superior colliculi caused by a mass lesions that had been surgically. They had all the symptoms mentioned above. We examined her with colour pupillography using the following stimuli: Red 605±20 nm, 4 s duration, 28 lux; blue 420±20 nm, 4 s duration, 28 lux and compared to averaged data from 17 normal subjects.
Pupil constriction to the red stimulus ranged from 4 to 23% related to baseline diameter (average 14.5%, in normal subjects average 40.1%). Pupil response to the blue stimulus ranged from 28 to 49% (average 39.1%, in normals 54.0%). This means that the red response was reduced by 64% whereas the blue response was only reduced by 28%, i.e. much less affected.
As we suppose that the blue stimulus addressed the ipRGC it must be assumed that their pathway to the midbrain somehow might bypass the pretectal area.
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