Table 1 Parameters provided by manufacturers of two automated infrared pupillometry devices: ^∗Neuroptics NPi-200 and ^∗∗NeuroLight-Algiscan

Pupil constriction to light

Diameter (mm)

<0.5 mm

Asymmetry (mm)

<0.5 mm

% Pupillary constriction to light (%PLR)

35–40%

Latency (s)

Constriction velocity (mm/s)

1.5 mm/s (<1 mm/s: pathological)

Dilation velocity (mm/s)

2.83

Neurological pupillary index (NPi)^∗

≥3

Pupil dilation to pain

Pupillary dilation reflex (%)^∗∗

33

Pupillary pain index^∗∗

Depends on intensity of stimulation [16,17,18,19]