Color Pupillography in Dorsal Midbrain Syndrome.

OBJECTIVE: The purpose of this study was to evaluate the pupil response to chromatic stimuli in patients with lesions in the dorsal midbrain and possibly gain new insights into the afferent pupillary pathways. METHODS: Color pupillography was performed in 5 patients with dorsal midbrain syndrome (DMS), and their results were compared with those of 20 healthy control subjects. We used full-field red stimuli (605 nm) that primarily address the rod/cone system and blue stimuli (420 nm) that preferentially activate intrinsically photosensitive retinal ganglion cells (ipRGCs) directly, with a duration of 4 seconds and a stimulus intensity of 28 lx corneal illumination under mesopic conditions. One eye was stimulated, and the consensual pupil response was recorded and analyzed. RESULTS: The pupillary light reflex in patients with DMS was reduced, differed in shape, and showed a prolonged latency time compared to normal subjects. The blue response was less affected than the red response: the mean maximal relative amplitude (M) was 15.8% (SD = 7.8) in patients with DMS compared with 43.0% (SD = 5.5) in normal subjects for red stimulation, and M = 40.8%, SD = 8.4 (DMS) with M = 58.3%, SD = 4.8 (normals) for blue stimulation. The reduction was 63% for red stimulation but only 30% for blue stimulation in patients with DMS. Moreover, there was a preserved postillumination pupil response to blue stimulation in DMS patients. CONCLUSIONS: In DMS, the melanopsin-mediated ipRGC pathway appeared relatively preserved.

Effect of age on the pupillomotor field.

To differentiate physiologic variation from visual field loss with pupillomotor perimetry, the effect of age on the normal pupillomotor field must be known. Given the absence of reported data, the authors aimed to analyze the effect of age on the pupillomotor field as measured with light stimuli of different properties. Subjects consisted of 23 healthy volunteers aged 20 to 28 years ("younger subjects") and 20 healthy volunteers aged 50 to 67 years ("older subjects"). Within a field of 20 degrees, a sequence of 25 focal light stimuli was performed repeatedly on a monitor. The pupil light reflex (PLR) was recorded to stimuli of different diameter and luminance under mesopic conditions. The mean amplitude of the PLR was calculated for each stimulus location and condition. Increasing stimulus luminance or size caused a larger PLR amplitude and a steeper decline of the PLR amplitude from the center to the periphery of the pupillomotor field. The older subjects had reduced mean PLR amplitude with a less pronounced decrease of PLR amplitude toward the field periphery. For the peripheral locations, the largest PLR amplitude was found in the temporal superior quadrants. There was considerable intra-individual test-retest variation in PLR amplitudes in younger and older subjects. The PLR is markedly reduced in older compared with younger subjects. Older subjects have a relatively less pronounced central peak of sensitivity. There are intra-individual test-retest variations in PLR amplitude and asymmetries in sensitivity within the normal pupillomotor field at any age. These findings must be considered in interpreting the results of pupillomotor perimetry.