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Quantitative classifications of binocular pupillary function from dynamic light stimulation

Poster Details

First Author: E.Janunts GERMANY

Co Author(s):    E. Chashchina   T. Bende   A. Langenbucher        

Abstract Details



Purpose:

To define quantitative indicators of pupillary reaction from short pulse illuminations by simultaneous bilateral monitoring of pupillary dynamic response (PDR) independent from the environmental light conditions, and to estimate the reliability of the new measures from sequence of repeat measurements.

Setting:

The monitoring of a pupil size has been performed using a commercially available pupillometer (PupilX, Albomed, Germany) equipped with an encapsulated hygienic face mask in 99 young healthy individuals in an age of 38.2 ± 14.7. Consecutive cross-sectional monocentric case series performed at the Department of Ophthalmology at the University Medical Center Homburg/Saar, Germany.

Methods:

Short pulses of white light with 50 ms pulse width and 64 Lux illuminance are exposed with a periodicity of 3 seconds in an alternating manner. Measurement sequence was 20 seconds with a frame rate of 30 Hz. 5 repeated measurements were performed. For each single measurement 12 graphs were obtained: 3 measurements per eye under 4 different conditions (stimulated in each eye separately and measured in both eyes simultaneously). For extracting clinically relevant information from this large data set, we propose averaging the 3 measurements per eye and then introducing a functional description of the averaged PDR by splitting each single curve into 3 segments and fitting into respective linear and exponential y(t)=a+b•exp(c•t) functions. After a short light pulse the pupil size was considered as constant at the very beginning followed by a rapid exponential decay, then smoothly slowing down and followed by an exponential increase tending to recover to baseline. The following parameters are extracted: time intervals for each segment dT1, dT2, and dT3, the pupil size differences for the pupil shrinkage dP1 and stretch dP2 as well as the exponential coefficients for respective segments (a, b, c). Descriptive analysis and reliability studies were performed.

Results:

Average values for the time interval after a trigger pulse dT1, and for exponential segments dT2 and dT3 were measured 0.23±0.02/ 0.53±0.14 / 2.12±0.24 seconds, respectively, with a side difference of 5.00±5.40 / 4.30±5.99 / 2.38±5.69 percent. The pupil size variation in dP1 and dP2 were measured 1.36±0.37 / 1.31±0.35 mm, respectively, with an anisocoria of 15.76±30.47 / 14.42±29.79 percent. a, b and c parameters were 3.49±0.92/ 1.63±0.38 / -6.27±1.22 for the exponential decay and 4.86±0.91/ 1.50±0.40 / -2.20±2.50 for the exponential recovery of the pupil diameter. Cronbach's alpha as a measure for reliability was calculated as follows: 0.58/0.34/0.46 for time intervals dT1, dT2, and dT3; 0.82/0.80 for pupil size variations dP1 and dP2; and exponential coefficients (a / b / c) for pupil shrinkage (0.91/0.85/0.78); and exponential coefficients (a / b / c) for pupil size recovery (0.95/0.93/0.57).

Conclusions:

No significant difference was detected for right or left eye stimulation. Therefore, for the simplicity, the examination could be restricted to only one or two scenarios: stimulated and measured on the same eye or only cross talk. In most cases the initial pupil size could be almost recovered within the intra-stimulated period of time. The data analysis showed that the pupil size variation could reliably be described by an exponential function and systematic time delay after a light pulse. FINANCIAL INTEREST: NONE

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