Pupil Examination in Children

Pupillary evaluation is a crucial part of every pediatric eye exam. It provides information about the structure of the eye as well as the afferent and efferent function of the eyes. It remains a quick and efficient test in the ocular evaluation. This chapter reviews the relevant neuroanatomy and the different components of the pupillary exam. The light-reflex and swinging flashlight tests are reviewed, as well as how a reverse afferent pupillary defect is detected. Clinical examples and pearls are provided to help the reader better understand the different aspects of the exam.

PyPlr: A versatile, integrated system of hardware and software for researching the human pupillary light reflex

We introduce PyPlr—a versatile, integrated system of hardware and software to support a broad spectrum of research applications concerning the human pupillary light reflex (PLR). PyPlr is a custom Python library for integrating a research-grade video-based eye-tracker system with a light source and streamlining stimulus design, optimisation and delivery, device synchronisation, and extraction, cleaning, and analysis of pupil data. We additionally describe how full-field, homogenous stimulation of the retina can be realised with a low-cost integrating sphere that serves as an alternative to a more complex Maxwellian view setup. Users can integrate their own light source, but we provide full native software support for a high-end, commercial research-grade 10-primary light engine that offers advanced control over the temporal and spectral properties of light stimuli as well as spectral calibration utilities. Here, we describe the hardware and software in detail and demonstrate its capabilities with two example applications: (1) pupillometer-style measurement and parametrisation of the PLR to flashes of white light, and (2) comparing the post-illumination pupil response (PIPR) to flashes of long and short-wavelength light. The system holds promise for researchers who would favour a flexible approach to studying the PLR and the ability to employ a wide range of temporally and spectrally varying stimuli, including simple narrowband stimuli.

Effect of central and peripheral cone- and rod-specific stimulation on the pupillary light reflex

Purpose To assess the effect of central and peripheral stimulation on the pupillary light reflex. The aim was to detect possible differences between cone- and rod-driven reactions. Methods Relative maximal pupil constriction amplitude (relMCA) and latency to constriction onset (latency) to cone- and rod-specific stimuli of 30 healthy participants (24 ± 5 years (standard deviation)) were measured using chromatic pupil campimetry. Cone- and rod-specific stimuli had different intensities and wavelengths according to the Standards in Pupillography. Five filled circles with radii of 3°, 5°, 10°, 20° and 40° and four rings with a constant outer radius of 40° and inner radii of 3°, 5°, 10° and 20° were used as stimuli. Results For cone-and rod-specific stimuli, relMCA increased with the stimulus area for both, circles and rings. However, increasing the area of a cone-specific ring by minimizing its inner radius with constant outer radius increased relMCA significantly stronger than the same did for a rod-specific ring. For cones and rods, a circle stimulus with a radius of 40° created a lower relMCA than the summation of the relMCAs to the corresponding ring and circle stimuli which combined create a 40° circle-stimulus. Latency was longer for rods than for cones. It decreased with increasing stimulus area for circle stimuli while it stayed nearly constant with increasing ring stimulus area for cone- and rod-specific stimuli. Conclusion The effect of central stimulation on relMCA is more dominant for cone-specific stimuli than for rod-specific stimuli while latency dynamics are similar for both conditions.

Pupillary evidence reveals the influence of positive thoughts on brightness perception

Our visual experience often varies based on momentary thoughts and feelings. For example,when positive thoughts are invoked, visual objects may appear brighter. However, it remainsunclear whether this phenomenological experience is driven by a genuine top-down modulation of brightness perception or by a mere response bias. To investigate this issue, here we use pupillometry as a more objective measure of perceived brightness. We asked participants to judge the brightness level of an iso-luminant gray color patch after evaluating the valence of a positive or negative word. We found that the gray color patch elicited greater pupillary light reflex and more frequent “bright” responses after observers had evaluated the valence of a positive word. As pupillary light reflex is unlikely driven by voluntary control or response bias, these results suggest that positive concepts can genuinely modulate brightness perception.

The Pupillary Light Reflex as a Biomarker of Concussion

The size of our pupils changes continuously in response to variations in ambient light levels, a process known as the pupillary light reflex (PLR). The PLR is not a simple reflex as its function is modulated by cognitive brain function and any long-term changes in brain function secondary to injury should cause a change in the parameters of the PLR. We performed a retrospective clinical review of the PLR of our patients using the BrightLamp Reflex iPhone app. The PLR variables of latency, maximum pupil diameter (MaxPD), minimum pupil diameter (MinPD), maximum constriction velocity (MCV), and the 75% recovery time (75% PRT) were associated with significant differences between subjects who had suffered a concussion and those that had not. There were also significant differences in PLR metrics over the life span and between genders and those subjects with and without symptoms. The differences in PLR metrics are modulated not only by concussion history but also by gender and whether or not the person has symptoms associated with a head injury. A concussive injury to the brain is associated with changes in the PLR that persist over the life span, representing biomarkers that might be used in clinical diagnosis, treatment, and decision making.

P105 Endocrine, autonomic and vascular function in children with Sleep Disordered Breathing

SDB is a risk factor for cardiovascular disease and co-exists with chronic endocrine disorders such as type II diabetes and metabolic syndrome. Children with SDB have increased blood flow velocity, an indicator of reduced vascular compliance and early vascular aging. Increased blood flow velocity is positively associated with sympathetic activity, increased arterial sympathetic nerve fibre density and endothelial damage. Whether changes in endocrine function occur concomitantly with altered autonomic and vascular function in children with SDB was assessed. Thirty six children scheduled for tonsillectomy underwent overnight polysomnography (SDB severity), pupil light reflex (autonomic function), fasting brachial artery blood flow assessment (vascular function - Doppler Ultrasound). Leptin and Ghrelin - both hormonal markers associated with sympathetic activity were measured in urine using ELISA and serum using MagPlex. The following dimensions of the dorsal lingual artery (tonsil) were measured – medial thickness, medial area, smooth muscle cell number/layers. We observed a positive correlation between serum and urine leptin and ghrelin concentrations. Increased blood flow velocity and arterial medial thickness were both associated with increased serum and urine leptin and ghrelin concentrations. Pupil light reflex was negatively associated with serum leptin and ghrelin levels. OAHI was positively correlated with leptin and ghrelin concentration (urine and serum) but not blood flow velocity. Blood flow velocity was inversely correlated with SpO2 nadir (REM). Our findings suggest that SDB has a global effect on the autonomic, vascular and endocrine systems.The impact of untreated paediatric SDB on the development of comorbidities in later life needs urgent attention.