Perceptions of daylight quality delivered by light transport systems

Light Transport Systems (LTS) (e.g lightpipes, fibre optics) can illuminate core areas within buildings with great potential for energy savings. However, they do not provide a clear connection to the outside like windows do, and their effects on people’s physiological and psychological health are not well understood. Furthermore, how people perceive LTS affects users’ acceptance of the device and its performance. The purpose of this research is to understand how occupants perceive and experience spaces illuminated by LTS. Two case studies of commercial buildings with LTS, located in Brisbane, Australia are assessed by qualitative (focus group interviews) and quantitative (measurement of daylight illuminances and luminance) methods. The data from interviews with occupants provide useful insight into the aspects of LTS design that are most relevant to positive perception of the luminous environment. Luminance measurements of the occupied spaces support the perception of the LTS reported by occupants: designs that create high contrast luminous environments are more likely to be perceived negatively.

Binocular summation improves performance to defocus-induced blur

PURPOSE. To assess whether there are any advantages of binocular over monocular vision under blur conditions. METHODS. We measured the effect of defocus, induced by positive lenses, on the pattern reversal Visual Evoked Potential (VEP) and on visual acuity (VA). Monocular (dominant eye) and binocular VEPs were recorded from thirteen volunteers (average age: 28±5 years, average spherical equivalent: -0.25±0.73 D) for defocus up to 2.00 D using positive powered lenses. VEPs were elicited using reversing 10 arcmin checks at a rate of 4 reversals/second. The stimulus subtended a circular field of 7 degrees with 100% contrast and mean luminance 30 cd/m2. VA was measured under the same conditions using ETDRS charts. All measurements were performed at 1m viewing distance with best spectacle sphero-cylindrical correction and natural pupils. RESULTS. With binocular stimulation, amplitudes and implicit times of the P100 component of the VEPs were greater and shorter, respectively, in all cases than for monocular stimulation. Mean binocular enhancement ratio in the P100 amplitude was 2.1 in-focus, increasing linearly with defocus to be 3.1 at +2.00 D defocus. Mean peak latency was 2.9 ms shorter in-focus with binocular than for monocular stimulation, with the difference increasing with defocus to 8.8 ms at +2.00 D. As for the VEP amplitude, VA was always better with binocular than with monocular vision, with the difference being greater for higher retinal blur. CONCLUSIONS. Both subjective and electrophysiological results show that binocular vision ameliorates the effect of defocus. The increased binocular facilitation observed with retinal blur may be due to the activation of a larger population of neurons at close-to-threshold detection under binocular stimulation.

Visual acuity with astigmatic blur

Abstract Purpose: To determine how high and low contrast visual acuities are affected by blur caused by crossed-cylinder lenses. Method: Crossed-cylinder lenses of power zero (no added lens), +0.12 DS/-0.25 DC, +0.25 DS/-0.50 DC and +0.37/-0.75 DC were placed over the correcting lenses of the right eyes of eight subjects. Negative cylinder axes used were 15-180 degrees in 15 degree step for the two higher crossed-cylinders and 30-180 degrees in 30 degree steps for the lowest crossed cylinder. Targets were single lines of letters based on the Bailey-Lovie chart. Successively smaller lines were read until the subject could not read any of the letters correctly. Two contrasts were used: high (100%) and low (10%). The screen luminance of 100 cd/m2, together with the room lighting, gave pupil sizes of 4.5 to 6 mm. Results: High contrast visual acuities were better than low contrast visual acuities by 0.1 to 0.2 log unit (1 to 2 chart lines) for the no added lens condition. Based on comparing the average of visual acuities for the 0.75 D crossed-cylinder with the best visual acuity for a given contrast and subject, the rates of change of visual acuity per unit blur strength were similar for high contrast (0.34± 0.05 logMAR/D) and low contrast (0.37± 0.09 logMAR/D). There were considerable asymmetry effects, with the average loss in visual acuity across the two contrasts and the 0.50D/0.75 D crossed-cylinders doubling between the 165± and 60± negative cylinder axes. The loss of visual acuity with 0.75 D crossed-cylinders was approximately twice times that occurring for defocus of the same blur strength. Conclusion: Small levels of crossed-cylinder blur (≤0.75D) produce losses in visual acuity that are dependent on the cylinder axis. 0.75 D crossed-cylinders produce losses in visual acuity that are twice those produced by defocus of the same blur strength.

Influence of field size on pupil diameter under photopic and mesopic light levels

Purpose: We investigated the interaction between adapting field size and luminance on pupil diameter when cones alone (photopic) or rods and cones (mesopic) were active. Method: Circular achromatic targets (1o to 24o diameter) were presented to eight young participants on a rectangular projector screen. The accommodative influence on pupil diameter was minimized using cycloplegia in the fixing right eye and the consensual pupil reflex was measured in the left eye. Target luminance was adjusted for each stimulus such that corneal flux density (product of field area and luminance) was constant at 3600 cd.deg2m-2 (photopic condition) and 1.49 cd.deg2m-2 (mesopic condition). Results: There were no statistically significant effects of adaptive field size on pupil diameter for either condition. Conclusion: If corneal flux density is kept constant, there will be no change in pupil diameter as the size of the stimulus field increases at either mesopic or photopic lighting levels up to at least 24°.

Dynamics of rod and cone photoreceptor interactions under mesopic light levels

Visual adaptation regulates contrast sensitivity during dynamically changing light conditions (Crawford, 1947; Hecht, Haig & Chase, 1937). These adaptation dynamics are unknown under dim (mesopic) light levels when the rod (R) and long (L), medium (M) and short (S) wavelength cone photoreceptor classes contribute to vision via interactions in shared non-opponent Magnocellular (MC), chromatically opponent Parvocellular (PC) and Koniocellular (KC) visual pathways (Dacey, 2000). This study investigated the time-course of adaptation and post-receptoral pathways mediating receptor specific rod and cone interactions under mesopic illumination. A four-primary photostimulator (Pokorny, Smithson & Quinlan, 2004) was used to independently control the activity of the four photoreceptor classes and their post-receptoral visual athways in human observers. In the first experiment, the contrast sensitivity and time-course of visual adaptation under mesopic illumination were measured for receptoral (L, S, R) and post-receptoral (LMS, LMSR, L-M) stimuli. An incremental (Rapid-ON) sawtooth conditioning pulse biased detection to ON-cells within the visual pathways and sensitivity was assayed relative to pulse onset using a briefly presented incremental probe that did not alter adaptation. Cone.Cone interactions with luminance stimuli (L cone, LMS, LMSR) reduced sensitivity by 15% and the time course of recovery was 25± 5ms-1 (μ ± SEM). PC mediated (+L-M) chromatic stimuli sensitivity loss was less (8%) than for luminance and recovery was slower (μ = 2.95 ± 0.05 ms-1), with KC mediated (S cone) chromatic stimuli showing a high sensitivity loss (38%) and the slowest recovery time (1.6 ± 0.2 ms-1). Rod-Rod interactions increased sensitivity by 20% and the time course of recovery was 0.7 ± 0.2 ms-1 (μ ± SD). Compared to these interaction types, Rod-Cone interactions reduced sensitivity to a lesser degree (5%) and showed the fastest recovery (μ = 43 ± 7 ms-1). In the second experiment, rod contribution to the magnocellular, parvocellular and koniocellular post-receptoral pathways under mesopic illumination was determined as a function of incremental stimulus duration and waveform (rectangular; sawtooth) using a rod colour match procedure (Cao, Pokorny & Smith, 2005; Cao, Pokorny, Smith & Zele, 2008a). For a 30% rod increment, a cone match required a decrease in [L/(L+M)] and an increase in [L+M] and [S/(L+M)], giving a greenish-blue and brighter appearance for probe durations of 75 ms or longer. Probe durations less than 75 ms showed an increase in [L+M] and no change in chromaticity [L/(L+M) or S/(L+M)], uggesting mediation by the MC pathway only for short duration rod stimuli. s We advance previous studies by determining the time-course and nature of photoreceptor specific retinal interactions in the three post-receptoral pathways under mesopic illumination. In the first experiment, the time-course of adaptation for ON cell processing was determined, revealing opponent cell facilitation in chromatic PC and KC pathways. The Rod-Rod and Rod-Cone data identify previously unknown interaction types that act to maintain contrast sensitivity during dynamically changing light conditions and improve the speed of light adaptation under mesopic light levels. The second experiment determined the degree of rod contribution to the inferred post-eceptoral pathways as a function of the temporal properties of the rod signal. r The understanding of the mechanisms underlying interactions between photoreceptors under mesopic illumination has implications for the study of retinal disease. Visual function has been shown to be reduced in persons with age-related maculopathy (ARM) risk genotypes prior to clinical signs of the disease (Feigl, Cao, Morris & Zele, 2011) and disturbances in rod-mediated adaptation have been shown in early phases of ARM (Dimitrov, Guymer, Zele, Anderson & Vingrys, 2008; Feigl, Brown, Lovie-Kitchin & Swann, 2005). Also, the understanding of retinal networks controlling vision enables the development of international lighting standards to optimise visual performance nder dim light levels (e.g. work-place environments, transportation).

Evaluation of the luminous environment in open-plan offices with skylights

High Dynamic Range (HDR) imaging was used to collect luminance information at workstations in 2 open-plan office buildings in Queensland, Australia: one lit by skylights, vertical windows and electric light, and another by skylights and electric light. This paper compares illuminance and luminance data collected in these offices with occupant feedback to evaluate these open-plan environments based on available and emerging metrics for visual comfort and glare. This study highlights issues of daylighting quality and measurement specific to open plan spaces. The results demonstrate that overhead glare is a serious threat to user acceptance of skylights, and that electric and daylight integration and controls have a major impact on the perception of daylighting quality. With regards to measurement of visual comfort it was found that the Daylight Glare Probability (DGP) gave poor agreement with occupant reports of discomfort glare in open-plan spaces with skylights, and the CIE Glare Index (CGI) gave the best agreement. Horizontal and vertical illuminances gave no indication of visual comfort in these spaces.

Post occupancy evaluations relating to discomfort glare : a study of green buildings in Brisbane

Glare indices have yet to be extensively tested in daylit open plan offices, as such there is no effective method to predict discomfort glare within these spaces. This study into discomfort glare in open plan green buildings targeted full-time employees, working under their everyday lighting conditions. Three green buildings in Brisbane were used for data collection, two were Green Star accredited and the other contained innovative daylighting strategies. Data were collected on full-time employees, mostly aged between 30 and 50 years, who broadly reflect the demographics of the wider working population in Australia. It was discovered 36 of the 64 respondents experienced discomfort from both electric and daylight sources at their workspace. The study used a specially tailored post-occupancy evaluation (POE) survey to help assess discomfort glare. Luminance maps extracted from High Dynamic Range (HDR) images were used to capture the luminous environment of the occupants. These were analysed using participant data and the program Evalglare. The physical results indicated no correlation with other developed glare metrics for daylight within these open plan green buildings, including the recently developed Daylight Glare Probability (DGP) Index. The strong influence of vertical illuminance, Ev in the DGP precludes the mostly contrast-based glare from windows observed in this investigation from forming a significant part of this index. Furthermore, critical assessment of the survey techniques used are considered. These will provide insight for further research into discomfort glare in the endeavour to fully develop a suitable glare metric.

Building envelope : performance optimisation processes for a daylight responsive architecture

Traditional shading design principles guide the vertical and horizontal orientation of fins, louvres and awnings being applied to orthogonal planar façades. Due to doubly curved envelopes characterising many contemporary designs, these rules of thumb are now not always applicable. Operable blinds attempt to regulate the fluctuating luminance of daylight and aid in shading direct sunlight. Mostly they remain closed, as workers are commonly too preoccupied to continually adjust them so a reliance on electrically powered lights remains a preference. To remedy these problems, the idea of what it is to sustainable enclose space is reconsidered through the geometric and kinetic optimisation of a parametric skin, with sunlight responsive modules that regulate interior light levels. This research concludes with an optimised design and also defines some unique metrics to gauge the design’s performance in terms of, the amount of exterior unobstructed view, its ability to shade direct sunlight and, its daylight glare probability.

A yellow filter improves response times to low-contrast targets and traffic hazards

Purpose Anecdotal evidence suggests that some sunglass users prefer yellow tints for outdoor activities, such as driving, and research has suggested that such tints improve the apparent contrast and brightness of real-world objects. The aim of this study was to establish whether yellow filters resulted in objective improvements in performance for visual tasks relevant to driving. Methods Response times of nine young (age [mean ± SD], 31.4 ± 6.7 years) and nine older (age, [mean ± SD], 74.6 ± 4.8) adults were measured using video presentations of traffic hazards (driving hazard perception task) and a simple low-contrast grating appeared at random peripheral locations on a computer screen. Response times were compared when participants wore a yellow filter (with and without a linear polarizer) versus a neutral density filter (with and without a linear polarizer). All lens combinations were matched to have similar luminance transmittances (˜27%). Results In the driving hazard perception task, the young but not the older participants responded significantly more rapidly to hazards when wearing a yellow filter than with a luminance-matched neutral density filter (mean difference, 450 milliseconds). In the low-contrast grating task, younger participants also responded more quickly for the yellow filter condition but only when combined with a polarizer. Although response times increased with increasing stimulus eccentricity for the low-contrast grating task, for the younger participants, this slowing of response times with increased eccentricity was reduced in the presence of a yellow filter, indicating that perception of more peripheral objects may be improved by this filter combination. Conclusions Yellow filters improve response times for younger adults for visual tasks relevant to driving.

Temporal dynamics of rod and cone photoreceptor interactions under mesopic illumination

Purpose: Photoreceptor interactions reduce the temporal bandwidth of the visual system under mesopic illumination. The dynamics of these interactions are not clear. This study investigated cone-cone and rod-cone interactions when the rod (R) and three cone (L, M, S) photoreceptor classes contribute to vision via shared post-receptoral pathways. Methods: A four-primary photostimulator independently controlled photoreceptor activity in human observers. To determine the temporal dynamics of receptoral (L, S, R) and post-receptoral (LMS, LMSR, +L-M) pathways (5 Td, 7° eccentricity) in Experiment 1, ON-pathway sensitivity was assayed with an incremental probe (25ms) presented relative to onset of an incremental sawtooth conditioning pulse (1000ms). To define the post-receptoral pathways mediating the rod stimulus, Experiment 2 matched the color appearance of increased rod activation (30% contrast, 25-1000ms; constant cone excitation) with cone stimuli (variable L+M, L/L+M, S/L+M; constant rod excitation). Results: Cone-cone interactions with luminance stimuli (LMS, LMSR, L-cone) reduced Weber contrast sensitivity by 13% and the time course of adaptation was 23.7±1ms (μ±SE). With chromatic stimuli (+L-M, S), cone pathway sensitivity was also reduced and recovery was slower (+L-M 8%, 2.9±0.1ms; S 38%, 1.5±0.3ms). Threshold patterns at ON-conditioning pulse onset were monophasic for luminance and biphasic for chromatic stimuli. Rod-rod interactions increased sensitivity(19%) with a recovery time of 0.7±0.2ms. Compared to cone-cone interactions, rod-cone interactions with luminance stimuli reduced sensitivity to a lesser degree (5%) with faster recovery (42.9±0.7ms). Rod-cone interactions were absent with chromatic stimuli. Experiment 2 showed that rod activation generated luminance (L+M) signals at all durations, and chromatic signals (L/L+M, S/L+M) for durations >75ms. Conclusions: Temporal dynamics of cone-cone interactions are consistent with contrast sensitivity loss in the MC pathway for luminance stimuli and chromatically opponent responses in the PC and KC pathway with chromatic stimuli. Rod-cone interactions limit contrast sensitivity loss during dynamic illumination changes and increase the speed of mesopic light adaptation. The change in relative weighting of the temporal rod signal within the major post-receptoral pathways modifies the sensitivity and dynamics of photoreceptor interactions.

Rod and cone pathway signaling and interaction under mesopic illumination

This study investigates the time-course and post-receptoral pathway signaling of photoreceptor interactions when the rod (R) and three cone (L, M, S) photoreceptor classes contribute to mesopic vision. A four-primary photostimulator independently controls photoreceptor activity in human observers. The first experiment defines the temporal adaptation response of receptoral (L-, S-cone, rod) and post-receptoral (LMS, LMSR,+L-M) signaling and interactions. Here we show that nonopponent cone-cone interactions (L-cone, LMS, LMSR) have monophasic temporal response patterns whereas opponent signals (+L-M, S-cone) show biphasic response patterns with slower recovery. By comparison, rod-cone interactions with nonopponent signals have faster adaptation responses and reduced sensitivity loss whereas opponent rod-cone interactions are small or absent. Additionally, the rod-rod interaction differs from these interaction types and acts to increase rod sensitivity due to temporal summation but with a slower time course. The second experiment shows that the temporal profile of the rod signal alters the relative rod contributions to the three primary post-receptoral pathways. We demonstrate that rod signals generate luminance (þLþM) signals mediated via the MC pathway with all rod temporal profiles and chromatic signals (L/LþM, S/LþM) in both the PC and KC pathways with durations .75 ms. Thus, we propose that the change in relative weighting of rod signals within the post-receptoral pathways contributes to the sensitivity and temporal response of rod and cone pathway signaling and interactions.

Binocular rivalry and visuospatial ability in individuals with schizophrenia

Visual abnormalities, both at the sensory input and the higher interpretive levels, have been associated with many of the symptoms of schizophrenia. Individuals with schizophrenia typically experience distortions of sensory perception, resulting in perceptual hallucinations and delusions that are related to the observed visual deficits. Disorganised speech, thinking and behaviour are commonly experienced by sufferers of the disorder, and have also been attributed to perceptual disturbances associated with anomalies in visual processing. Compounding these issues are marked deficits in cognitive functioning that are observed in approximately 80% of those with schizophrenia. Cognitive impairments associated with schizophrenia include: difficulty with concentration and memory (i.e. working, visual and verbal), an impaired ability to process complex information, response inhibition and deficits in speed of processing, visual and verbal learning. Deficits in sustained attention or vigilance, poor executive functioning such as poor reasoning, problem solving, and social cognition, are all influenced by impaired visual processing. These symptoms impact on the internal perceptual world of those with schizophrenia, and hamper their ability to navigate their external environment. Visual processing abnormalities in schizophrenia are likely to worsen personal, social and occupational functioning. Binocular rivalry provides a unique opportunity to investigate the processes involved in visual awareness and visual perception. Binocular rivalry is the alternation of perceptual images that occurs when conflicting visual stimuli are presented to each eye in the same retinal location. The observer perceives the opposing images in an alternating fashion, despite the sensory input to each eye remaining constant. Binocular rivalry tasks have been developed to investigate specific parts of the visual system. The research presented in this Thesis provides an explorative investigation into binocular rivalry in schizophrenia, using the method of Pettigrew and Miller (1998) and comparing individuals with schizophrenia to healthy controls. This method allows manipulations to the spatial and temporal frequency, luminance contrast and chromaticity of the visual stimuli. Manipulations to the rival stimuli affect the rate of binocular rivalry alternations and the time spent perceiving each image (dominance duration). Binocular rivalry rate and dominance durations provide useful measures to investigate aspects of visual neural processing that lead to the perceptual disturbances and cognitive dysfunction attributed to schizophrenia. However, despite this promise the binocular rivalry phenomenon has not been extensively explored in schizophrenia to date. Following a review of the literature, the research in this Thesis examined individual variation in binocular rivalry. The initial study (Chapter 2) explored the effect of systematically altering the properties of the stimuli (i.e. spatial and temporal frequency, luminance contrast and chromaticity) on binocular rivalry rate and dominance durations in healthy individuals (n=20). The findings showed that altering the stimuli with respect to temporal frequency and luminance contrast significantly affected rate. This is significant as processing of temporal frequency and luminance contrast have consistently been demonstrated to be abnormal in schizophrenia. The current research then explored binocular rivalry in schizophrenia. The primary research question was, "Are binocular rivalry rates and dominance durations recorded in participants with schizophrenia different to those of the controls?" In this second study binocular rivalry data that were collected using low- and highstrength binocular rivalry were compared to alternations recorded during a monocular rivalry task, the Necker Cube task to replicate and advance the work of Miller et al., (2003). Participants with schizophrenia (n=20) recorded fewer alternations (i.e. slower alternation rates) than control participants (n=20) on both binocular rivalry tasks, however no difference was observed between the groups on the Necker cube task. Magnocellular and parvocellular visual pathways, thought to be abnormal in schizophrenia, were also investigated in binocular rivalry. The binocular rivalry stimuli used in this third study (Chapter 4) were altered to bias the task for one of these two pathways. Participants with schizophrenia recorded slower binocular rivalry rates than controls in both binocular rivalry tasks. Using a ‘within subject design’, binocular rivalry data were compared to data collected from a backwardmasking task widely accepted to bias both these pathways. Based on these data, a model of binocular rivalry, based on the magnocellular and parvocellular pathways that contribute to the dorsal and ventral visual streams, was developed. Binocular rivalry rates were compared with performance on the Benton’s Judgment of Line Orientation task, in individuals with schizophrenia compared to healthy controls (Chapter 5). The Benton’s Judgment of Line Orientation task is widely accepted to be processed within the right cerebral hemisphere, making it an appropriate task to investigate the role of the cerebral hemispheres in binocular rivalry, and to investigate the inter-hemispheric switching hypothesis of binocular rivalry proposed by Pettigrew and Miller (1998, 2003). The data were suggestive of intra-hemispheric rather than an inter-hemispheric visual processing in binocular rivalry. Neurotransmitter involvement in binocular rivalry, backward masking and Judgment of Line Orientation in schizophrenia were investigated using a genetic indicator of dopamine receptor distribution and functioning; the presence of the Taq1 allele of the dopamine D2 receptor (DRD2) receptor gene. This final study (Chapter 6) explored whether the presence of the Taq1 allele of the DRD2 receptor gene, and thus, by inference the distribution of dopamine receptors and dopamine function, accounted for the large individual variation in binocular rivalry. The presence of the Taq1 allele was associated with slower binocular rivalry rates or poorer performance in the backward masking and Judgment of Line Orientation tasks seen in the group with schizophrenia. This Thesis has contributed to what is known about binocular rivalry in schizophrenia. Consistently slower binocular rivalry rates were observed in participants with schizophrenia, indicating abnormally-slow visual processing in this group. These data support previous studies reporting visual processing abnormalities in schizophrenia and suggest that a slow binocular rivalry rate is not a feature specific to bipolar disorder, but may be a feature of disorders with psychotic features generally. The contributions of the magnocellular or dorsal pathways and parvocellular or ventral pathways to binocular rivalry, and therefore to perceptual awareness, were investigated. The data presented supported the view that the magnocellular system initiates perceptual awareness of an image and the parvocellular system maintains the perception of the image, making it available to higher level processing occurring within the cortical hemispheres. Abnormal magnocellular and parvocellular processing may both contribute to perceptual disturbances that ultimately contribute to the cognitive dysfunction associated with schizophrenia. An alternative model of binocular rivalry based on these observations was proposed.

Discomfort glare in open plan green buildings

This study presents the largest-known, investigation on discomfort glare with 493 surveys collected from five green buildings in Brisbane, Australia. The study was conducted on full-time employees, working under their everyday lighting conditions, all of whom had no affiliation with the research institution. The survey consisted of a specially tailored questionnaire to assess potential factors relating to discomfort glare. Luminance maps extracted from high dynamic range (HDR) images were used to capture the luminous environment of the occupants. Occupants who experienced glare on their monitor and/or electric glare were excluded from analysis leaving 419 available surveys. Occupants were more sensitive to glare than any of the tested indices accounted for. A new index, the UGP was developed to take into account the scope of results in the investigation. The index is based on a linear transformation of the UGR to calculate a probability of disturbed persons. However all glare indices had some correlation to discomfort, and statistically there was no difference between the DGI, UGR and CGI. The UGP broadly reflects the demographics of the working population in Australia and the new index is applicable to open plan green buildings.

Pyridine-incorporated dihexylquaterthiophene : a novel blue emitter for organic light emitting diodes (OLEDs)

The synthesis and characterisation of 2,5-bis(5′-hexyl-[2,2′- bithiophen]-5-yl)pyridine (Th4PY) and its use as a blue emitter in organic light emitting diodes (OLEDs) is reported. Th4PY was synthesised in high yield using a straightforward Suzuki coupling route with commercially available starting materials. As Th4PY is both soluble and has low molecular weight, blue OLEDs were fabricated using both spin-coating and vacuum deposition thin film processing techniques to study the effect of processing on device performance. OLED devices using a spin-coated layer consisting of 4′,4′′- tris(N-carbazolyl)triphenylamine (TCTA) and 2-(4-biphenylyl)-5-(4-tert- butylphenyl)-1,3,4-oxadiazole (PBD) as a host matrix together with Th4PY as emitter exhibited highly efficient sky-blue emission with a low turn-on voltage of 3V, a maximum brightness close to 15000cdm-2 at 8V, and a maximum luminous efficiency of 7.4cdA -1 (6.3lmW -1) with CIE coordinates of x≤0.212, y≤0.320. The device performance characteristics are compared using various matrices and processing techniques. The promising sky-blue OLED performance, solution processability, and ambient stability make Th4PY a promising blue emitter for application in OLEDs.

Effects of pupil center shift on ocular aberrations

Purpose: To investigate effects of pupil shifts, occurring with changes in luminance and accommodation stimuli, on refraction components and higher-order aberrations. Method: Participants were young and older groups (n=20, 22±2 years, age range 18–25 years; n=19, 49±4 years, 45–58 years). Aberrations/refractions at 4 mm and 3 mm diameters were compared between centered and decentered pupils for low (background 0.01cd/m², 0D), and high (6100cd/m², 4D or 6D) stimuli. Decentration was the difference between pupil centers for low and high stimuli. Clinical important changes with decentration were: M ±0.50D or ±0.25D, J180 and J45 ±0.25D or ±0.125D, HORMS ±0.05m, C(3, 1) ±0.05m, C(4, 0) ±0.05m. Results: Because of small pupil shifts in most participants (mean 0.26mm), there were few important changes in most refraction components and higher-order aberration terms. However, M changed by >0.25 D for a third of participants with 4mm pupils. When determining refractions from 2nd-6th order aberration coefficients, the more stringent criteria gave 76/ 534 (14%) possible important changes. Some participants had large pupil shifts with considerable aberration changes. Comparisons at the high stimulus were possible for only 11 participants because of small pupils. When refractions were determined from 2nd order aberration coefficients only, there were only 35 (7%) important changes for the more stringent criteria. Conclusion: Usually pupil shifts with changes in stimulus conditions have little influence on aberrations, but they can with high shifts. The number of aberrations orders that are considered as contributing to refraction influences the proportion of cases that might be considered clinically important.