Optimal timing of retinal scanning during dark adaptation, in the presence of fixation on a target: the role of pupil size dynamics

Acceleration of inferred neural responses to oddball targets in an individual with bilateral amygdala lesion compared to healthy controls

Detecting unusual auditory stimuli is crucial for discovering potential threat. Locus coeruleus (LC), which coordinates attention, and amygdala, which is implicated in resource prioritization, both respond to deviant sounds. Evidence concerning their interaction, however, is sparse. Seeking to elucidate if human amygdala affects estimated LC activity during this process, we recorded pupillary responses during an auditory oddball and an illuminance change task, in a female with bilateral amygdala lesions (BG) and in n = 23 matched controls. Neural input in response to oddballs was estimated via pupil dilation, a reported proxy of LC activity, harnessing a linear-time invariant system and individual pupillary dilation response function (IRF) inferred from illuminance responses. While oddball recognition remained intact, estimated LC input for BG was compacted to an impulse rather than the prolonged waveform seen in healthy controls. This impulse had the earliest response mean and highest kurtosis in the sample. As a secondary finding, BG showed enhanced early pupillary constriction to darkness. These findings suggest that LC-amygdala communication is required to sustain LC activity in response to anomalous sounds. Our results provide further evidence for amygdala involvement in processing deviant sound targets, although it is not required for their behavioral recognition.

Pupil Constrictions and Their Associations With Increased Negative Affect During Responses to Recalled Memories of Interpersonal Stress

Abstract. Pupil diameter change is indicative of emotional processing. Most previous findings regarding pupillary response and emotion have reported that the pupil enlarges in response to the presentation of emotional perceptual stimuli (e.g., visual images) within several seconds. It is considered that such stimuli activate the sympathetic nervous system, leading to pupil dilation. In order to examine the effects of emotions similar to daily emotional experiences of mood, the present study examined pupil diameter changes and their relationships with subjective emotional changes while recalling a topic of stressful interpersonal events in daily life. The data of 20 university students (11 males, Mage = 20.36 ± 2.38 years; 9 females, Mage = 22.33 ± 3.57) were analyzed. In the experimental task, participants were instructed to recall their memories concerning the topic through instructions and questions presented on a monitor, which proceeded at their own pace, through a key press. Subsequently, after baseline and instruction periods, participants were instructed to freely recall their memories. They were then asked to respond silently to a series of questions concerning the freely recalled memories. In the analysis, we compared the pupil diameters between these different periods and observed that pupil diameters significantly decreased during the response period relative to the free recall or baseline periods. Furthermore, pupil constrictions during the response period were negatively correlated with increases in negative affect scale scores. Pupil constriction, which is indicative of decreased arousal level and parasympathetic activation, was presumably caused by multiple factors including less cognitive difficulty and a relatively long experimental task period. As the result of a less tonic mode in the response period, the attention of participants might be more successfully focused on ongoing tasks, which might lead to optimal performance in recalling memories, possibly leading to correlations between pupil diameter and negative emotional changes.

Higher order aberrations and axial elongation in combined 0.01% atropine with orthokeratology for myopia control

PURPOSE

To compare the changes in higher order aberrations (HOA's) for photopic and mesopic pupil diameters in children undergoing orthokeratology treatment (OK) or combined 0.01% atropine with orthokeratology treatment (AOK), and their association with axial elongation.

METHODS

Children aged 6 to <11 years with 1.00-4.00 D of myopia were randomly assigned to each treatment group. Photopic and mesopic pupil diameters were quantified using automated pupillometry and HOA's were measured with a Hartmann-Shack aberrometer and Badal system to control for accommodation. HOA's were rescaled to photopic and mesopic pupil diameters and fitted with a 6^th order Zernike polynomial expansion. Axial length was measured using an optical biometer under cycloplegia.

RESULTS

Baseline and six-month data from 25 AOK and 28 OK participants were analysed. At the six-month visit, pupil diameter was larger in the AOK group under photopic conditions (3.70 ± 0.42 vs 3.12 ± 0.33 mm, p < 0.001), along with a range of HOA metrics [3^rd to 6^th order and higher order root mean square error values (HO RMS), all p ≤ 0.003] and individual Zernike terms (primary spherical aberration, and oblique quadrafoil, both p ≤ 0.03). Axial elongation was greater in the OK treatment group (0.05 ± 0.08 vs -0.01 ± 0.12 mm, p = 0.02). In the AOK group, axial elongation was correlated with the increase in photopic pupil diameter (r = -0.45, p = 0.02) and with several HOA metrics; however, these associations were not observed in the OK group.

CONCLUSION

AOK treatment resulted in increased photopic pupil size and HOA's, and significantly less axial elongation over a six-month period compared to OK treatment alone. The improved myopia control observed with combination 0.01% atropine and orthokeratology may be a result of an enhanced optical effect due to a larger photopic pupil size.

Reproducibility and normal values of static pupil diameters

Purpose:

To provide additional information on normal values of static pupil diameter measurements for binocular infrared pupillometry with PupilX, a commercial pupillometer, and assess the reproducibility of this device’s measurements.

Methods:

The pupil diameters from 91 study participants with normal eyes with an average age of 39.7 years (SD 16.4 years) were measured with PupilX under scotopic (0 lx), mesopic (1 lx), and photopic (16 lx) illumination. To assess the repeatability of the device, each measurement was repeated 5 times.

Results:

The mean pupil diameters were 6.5 mm (SD 1.3 mm), 5.5 mm (SD 1.2 mm), and 4.03 mm (SD 0.9 mm) under scotopic, mesopic, and photopic illumination. Left and right eyes showed no difference in mean pupil diameters. The mean unsigned anisocoria was 0.26 mm (SD 0.32 mm) under scotopic, 0.26 mm (SD 0.27 mm) under mesopic, and 0.19 mm (SD 0.19 mm) under photopic illumination. The decrease in pupil diameter with age was largest for scotopic (≈0.057 mm/y) and smallest for photopic illumination (≈0.025 mm/y). The repeatability of the pupillometer was better than 0.2 mm.

Conclusions:

This study provides reference values for age- and light-related pupil diameters measured with the PupilX digital pupillometer in normal subjects.

A no-moving-parts sensor for the detection of eye fixation using polarised light and retinal birefringence information

Polarised near-infra-red light is reflected from the foveal area in a detectable bow-tie pattern of polarisation states, offering the opportunity for eye tracking. A coaxial optical transducer was developed, consisting of a laser diode, a polariser, a filter, and a photodetector. Several such transducers may be used to interrogate different spots on the retina, thus eliminating the requirement for scanning systems with moving parts. To test the signal quality obtainable, using just one transducer, a test subject was asked to fixate successively on twelve targets located on a circle around the transducer, to simulate the retina's being interrogated by twelve sensors placed on a 3⁰ diameter circle surrounding the projection of the fovea. The resulting signal is close to the "ideal" sine wave that would have been recorded from a propeller-type birefringence pattern from a human fovea. The transducer can be used in the detection of fixation for medical and other purposes. It does not require calibration, strict restrictions on head position, or head-mounted appliances.

New pediatric vision screener, part II: electronics, software, signal processing and validation

Background

We have developed an improved pediatric vision screener (PVS) that can reliably detect central fixation, eye alignment and focus. The instrument identifies risk factors for amblyopia, namely eye misalignment and defocus.

Methods

The device uses the birefringence of the human fovea (the most sensitive part of the retina). The optics have been reported in more detail previously. The present article focuses on the electronics and the analysis algorithms used. The objective of this study was to optimize the analog design, data acquisition, noise suppression techniques, the classification algorithms and the decision making thresholds, as well as to validate the performance of the research instrument on an initial group of young test subjects—18 patients with known vision abnormalities (eight male and 10 female), ages 4–25 (only one above 18) and 19 controls with proven lack of vision issues. Four statistical methods were used to derive decision making thresholds that would best separate patients with abnormalities from controls. Sensitivity and specificity were calculated for each method, and the most suitable one was selected.

Results

Both the central fixation and the focus detection criteria worked robustly and allowed reliable separation between normal test subjects and symptomatic subjects. The sensitivity of the instrument was 100 % for both central fixation and focus detection. The specificity was 100 % for central fixation and 89.5 % for focus detection. The overall sensitivity was 100 % and the overall specificity was 94.7 %.

Conclusions

Despite the relatively small initial sample size, we believe that the PVS instrument design, the analysis methods employed, and the device as a whole, will prove valuable for mass screening of children.