Digital Pupillometry in Normal Subjects

Abstract

The aim of this study was to evaluate the pupil size of normal subjects at different illumination levels with a novel pupillometer. The pupil size of healthy study participants was measured with an infraredvideo PupilX pupillometer (MEye Tech GmbH, Alsdorf, Germany) at five different illumination levels (0, 0.5, 4, 32, and 250 lux). Measurements were performed by the same investigator. Ninety images were executed during a measurement period of 3 seconds. The absolute linear camera resolution was approximately 20 pixels per mm. This cross-sectional study analysed 490 eyes of 245 subjects (mean age: 51.9 ± 18.3 years, range: 6-87 years). On average, pupil diameter decreased with increasing light intensities for both eyes, with a mean pupil diameter of 5.39 ± 1.04 mm at 0 lux, 5.20 ± 1.00 mm at 0.5 lux, 4.70 ± 0.97 mm at 4 lux, 3.74 ± 0.78 mm at 32 lux, and 2.84 ± 0.50 mm at 250 lux illumination. Furthermore, it was found that anisocoria increased by 0.03 mm per life decade for all illumination levels (R 2 = 0.43). Anisocoria was higher under scotopic and mesopic conditions. This study provides additional information to the current knowledge concerning age-and light-related pupil size and anisocoria as a baseline for future patient studies. ARTICLE HISTORY

Physiologic anisocoria under various lighting conditions

“… 2 , 3 , 12 Also, as reported previously, the prevalence of anisocoria increases under dim illumination levels, with anisocoria being 1.5 times greater at scotopic light levels compared with the photopic light levels. 1 , 4 , 7 This may be in part due to an imbalance in resting sympathetic tone, or due to unequal fibrous iris stroma that increases resistance as the eye dilates, causing larger differences in pupil diameter under dim illumination levels. 16 , 17 …”

“…There is also no consensus on whether anisocoria that disappears under varied lighting conditions is considered physiologic or random pupillary noise. 2 – 4 , 7 , 10 , 11 Meyer used a “perceptible” difference in pupil size as a threshold for anisocoria and was among the first to record the prevalence of physiologic anisocoria in a healthy population. 12 Loewenfeld later used a criterion of >0.4 mm difference in pupil diameter as a threshold for physiologic anisocoria in a healthy population and found the prevalence to be about 20%.…”

“… 8 Given the variation in thresholds and lighting conditions used, it is not surprising that there is a wide range of reported prevalence of physiologic anisocoria in the literature. 2 , 3 , 7 , 10 , 13 …”

“…10 There have been several studies reporting the prevalence of physiologic anisocoria using these newer devices, yet these studies lack procedural standardization and utilize inconsistent luminance levels. 3 , 6 , 7 , 10 , 15 …”

Assessing Saccadic Eye Movements With Head-Mounted Display Virtual Reality Technology

“…The study observed the pupil diameter of 5.4 ± 0.7 mm and 3.9 ± 0.4 mm for the subjects aged between 21 and 30 years and of 4.4 ± 0.5 mm and 3.5 ± 0.5 mm for the subjects aged between 31 and 40 years in mesopic and low photopic visions respectively. Another study also inspected the changes of pupillary response at five luminance levels: 0, 0.5, 4, 32, and 250 cd/m 2 in 245 healthy population (mean age: 51.9 ± 18.3 years; age range: 6 ∼ 87 years) (38). The research found a mean pupil diameter of 5.39 ± 1.04 mm at 0 cd/m 2 , 5.20 ± 1.00 mm at 0.5 cd/m 2 , 4.70 ± 0.97 mm at 4 cd/m 2 , 3.74 ± 0.78 mm at 32 cd/m 2 , and 2.84 ± 0.50 mm at 250 cd/m 2 and decreasing pupil size with increasing age.…”