Static and dynamic characteristics of the pupil light reflex obtained in Indian eyes using a hand-held, objective pupillometer
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Published on: April 11, 2019
Erum Nisha1, Rahul Negi1, Tithi Halder2
1Center for Technology Innovation, Kallam Anji Reddy Campus L V Prasad Eye Institute, Road 2 Banjara Hill, Hyderabad, Telangana, 500034, India.
Purpose:
To establish the baseline data of static and dynamic characteristics of the pupil light reflex in Indian eyes across a wide age range using Pupil N, a newly developed handheld, objective pupillometer and thereby compare the present outcomes with a comparable dataset in Indian eyes obtained using the NPi-200, the current standard of care in objective pupillometry.
Methods:
Pupil N elicits the light reflex by delivering two 1-s-long visible light pulses of 125 lx intensity onto the eye with 4-s of interstimulus interval, all after initial 6-s of dark adaptation. Pupil diameters recorded using an infrared sensitive camera (30 fps) are processed using a commercial smartphone to derive six outcome variables: pre- and post-stimulated diameter, miosis (normalized to pre-stimulation values), constriction and dilation peak velocities and response latency. Baseline data were collected in this study in both eyes on 290 healthy participants (3-86 years of age) and the right eye data of adults were compared with those obtained using NPi-200 by Rattan et al. [37].
Results:
Baseline values calculated for each age decade showed younger eyes having larger pre-and post-stimulation diameters, faster constriction and dilation peak velocities, relative to older eyes (p < 0.001). The magnitude of miosis and response latency were similar across ages, except for larger miosis and shorter latencies in the first decade of life (p < 0.001). Data trends were similar to Rattan et al., but the absolute values differed across outcome variables (p < 0.001), except for pre-stimulation diameter (p = 0.06).
Conclusions:
The baseline values of pupil light reflex reported here for Pupil N may be used as future reference standards for interpreting data of individuals with neurological dysfunction. The inter-device differences reported here call for caution while using these devices interchangeably for eliciting/interpreting the pupil light reflex in clinical and research environments.
