The post-illumination pupil response and sleep-wake rhythm in patients with a history of optic chiasm compression - Nederlandse Vereniging voor Endocrinologie

RATIONALE
A history of optic chiasm compression in patients with sellar tumors is associated with an altered sleep-wake rhythm. The optic chiasm contains axons of intrinsically photosensitive retinal ganglion cells (ipRGCs) that mediate photoentrainment of the suprachiasmatic nucleus, our biological clock. Compression could impair this entrainment. The post-illumination pupil response (PIPR) after blue light is a unique indicator of ipRGC function. In this study we compare the PIPR and parameters of sleep-wake rhythm between hypopituitarism patients with and without a history of chiasm compression.

METHODS
This ongoing observational study uses a chromatic pupillometry protocol of five 5-minute blocks. The primary outcome parameters are defined as the absolute (PIPR-mm) and the relative (PIPR-%) difference between baseline and post-blue-stimulus pupil diameter averaged over the 2^nd-4^th minute of the corresponding block. Sleep-wake rhythm is assessed through 1-week actigraphy. For sufficient power, 25 patients are included in each group.

RESULTS
At this interim analysis, pupillometry results of 23 patients in the chiasm compression group (CC+) and 20 patients in the control group (CC-) are presented. Groups did not differ in relevant clinical characteristics or in baseline pupil diameter. No significant differences were found in PIPR-mm (mean±SD, CC+ 1.70 ±0.74mm and CC- 2.14 ±0.92mm; p=0.90) or PIPR-% (CC+ 36.80 ±10.97% and CC- 41.36 ±9.66%; p=0.16). When inspecting the normalized (i.e. relative to baseline) pupil diameter data, a less sustained PIPR in the CC+ group was observed, with a diameter difference reaching significance during the last minute of the post-blue block (CC+ 67.77 ±12.34% and CC- 59.28 ±8.64%; p=0.01).

CONCLUSION
These preliminary results do not show significant differences in our primary PIPR outcomes. However, a less sustained PIPR is demonstrated in the CC+ group, which might correspond to less robust ipRGC transduction. Completion of inclusion is warranted in order to make well-founded conclusions. This is expected at the end of 2018.