Mesopic Research Articles

A Paradox of LED Road Lighting: Reducing Light Pollution Is Not Always Linked to Energy Savings

A variety of LED types can be employed for street and road lighting purposes. White phosphor-converted LEDs represent the most widely used option. However, amber LEDs are increasingly being used to reduce some negative effects associated with light pollution. These LEDs can be manufactured using both phosphor-converted and monochromatic direct chip technologies. This paper addresses the link between the reduction in short-wavelength light emissions which contribute to sky glow and the energy efficiency of LED-based road lighting. This paper focuses on an example illustrating the common misconception that reducing light pollution also means saving energy. Through the consideration of how spectral power distribution influences both mesopic vision and the amount of emitted blue light, it has been concluded that while monochromatic direct amber LEDs consume more energy than their white or amber phosphor-converted counterparts, their use in outdoor lighting is justifiable due to their potential effects of reducing sky brightness.

Orthokeratology in road traffic – a random sample

Purpose. The German regulation on granting persons permission to drive on the road specifies minimum visual requirements for obtaining a driving licence. The aim of this pilot study was to determine orthokeratology-related diurnal variations in visual acuity, contrast sensitivity and mesopic vision, as well as sensitivity to glare, and to verify compliance with the requirements for obtaining a driving licence. Material and Methods. Ten orthokeratology lens wearers (26.0 ± 7.1 years) with myopia of −2.43 ± 0.97 D and astig- matism of −0.31 ± 0.41 D were tested twice daily (08:30 and 20:30 h) with the Binoptometer 4P (Oculus, Wetzlar, Ger- many). Monocular and binocular visual acuity were tested according to the ISO 8596 and compared with the visual acu- ity requirements for obtaining a driving licence. In addition, binocular contrast and mesopic vision as well as sensitivity to glare were tested in both exams. Differences between the morning and evening examinations were determined using the paired t-test or the Wilcoxon signed-rank test (for non-normally distributed data). Results. There was no statistically significant difference between monocular visual acuity (logMAR) in the morning (right −0.07 ± 0.16; left −0.03 ± 0.15) and evening (right −0.09 ± 0.14; left −0.06 ± 0.17) (p = 0.875; p = 0.353) or binocular visual acuity in the morning (−0.11 ± 0.15) and evening (−0.13 ± 0.13) (p = 0.500). Decimal visual acuity ranged monocularly from 0.63 to 2.00 and binocularly from 0.70 to 2.00. This corre- sponds to the threshold value of an ophthalmological as- sessment for visual acuity of the better eye or for a binocular visual acuity of 0.5. There was no statistically significant difference between the quality of contrast vision in the morning (mean We- ber contrast 11.5 ± 3.4 %) and in the evening (15.5 ± 9.3 %) (p = 0.070), and mesopic vision and glare sensitivity in the morning (both 0.27 ± 0.09 logCS) and in the evening (both 0.27 ± 0.09 logCS) (p = 1.000). Conclusion. Visual acuity, contrast sensitivity, mesopic vision and sensitivity to glare were stable throughout the day in this sample for orthokeratology lens wearers. The requirements of the eye test needed to drive were fulfilled by all but one of the participants in the standard eye test, both in the morning and evening examinations. A more comprehensive eye test was also carried out. This was passed by all test subjects, both in the morning and evening examinations. Keywords Orthokeratology, driving licence regulation, ISO 8596, ophthalmological assessment, mesopic vision, sensitivity to glare

Agreement between Two Devices for Measuring Pupil Diameter in Patients Implanted with Multifocal Intraocular Lenses.

The purpose of this study was to evaluate the agreement between three methods for measuring pupil size in patients implanted with multifocal intraocular lenses (MIOLs): Keratograph 5M (K5M), Pentacam AXL Wave (PW), and a simple hand ruler. Sixty-nine subjects implanted with MIOLs and measured at the three-month follow-up visit were included in this retrospective analysis. K5M and PW were used to measure the photopic (PP) and mesopic (MP) pupil sizes, and a hand ruler was used to measure the pupil under environmental light conditions (135 lux). The Bland-Altman method with its limits (LoAs) was used to assess the agreement. The median PP was 2.8, 2.95, and 3 mm for K5M, PW, and the ruler, respectively (p < 0.05). Differences in PP were statistically significant for all paired comparisons (p < 0.0005) except between PW and the ruler (p = 0.44). The LoAs for the difference in PP between K5M and PW was 0.63 mm. The mean difference for MP between K5M and PW was 0.04 mm (p = 0.34) with LoAs of 0.72 mm. MP measured with K5M and PW could be considered interchangeable, although a correction of -0.3 mm (IC95%: -0.23 to -0.39) should be applied to PP measured with PW to attain the K5M mean.

Road lighting and mesopic vision

Human beings perceive information from the environment by using their sense organs. Vision is believed to provide the most information. There are three categories of vision: scotopic, mesopic, and photopic vision. The activity of two types of light-sensitive receptors in the eye, cones and rods, is different for each category. Cones and rods have a unique ability to adapt to different levels of illumination. Adaptation is the ability of the human eye to adapt to changing lighting conditions. Thanks to this mechanism, the human visual system has the ability to operate in a very wide range of pupil illuminations, that is, at different adaptive levels. At very low adaptive levels, only the rods are active, and the vision is called scotopic. As adaptive levels increase, starting at 0.005 cd/m2, the rods become less active, meanwhile the cones become active, and then the vision is called mesopic. At adaptive levels above 5 cd/m2, only cones are active, and the vision becomes photopic. Cones and rods have different spectral sensitivities: rods are more sensitive to short wavelengths, while cones are most sensitive within the visible spectral range. Cones are concentrated mainly in the part of the retina of the eye that is used for direct (on-line) vision, while rods are localized only in the areas used for peripheral vision. As a result, in case of mesopic vision, the peripheral vision becomes better with light sources that have a relatively large component of short wavelengths. The same is true for the subjective perception of brightness. At low adaptation levels, more rods become active, and thus these benefits are greater at low illumination levels.&#x0D; Since photometric units are based on photopic vision, these advantages are not obvious. Thus, the correction factors should be determined according to the spectrum of light sources, which is characterized by the S/P ratio, and the illumination levels of road lighting.&#x0D; The International Commission on Illumination has prepared a standard (CIE 115:2010 Lighting of roads for motor and pedestrian traffic). The main goals of road lighting are to ensure visual performance, visual comfort and to keep drivers alert.

Design and Optical Analysis of a Refractive Aspheric Intraocular Lens with Extended Depth of Focus

To obtain a continuous range of clear vision for pseudophakic eyes, a design of intraocular lens (IOL) with extended depth of focus (EDoF) was proposed. The IOL was optimized with a multi-configuration approach based on a pseudophakic eye model and the optical performances of the designed IOL were analyzed. The modulation transfer function (MTF) values remain above 0.2 at 50 lp/mm for object distance ranging from 0.35 m to infinity in both photopic vision and mesopic vision over a field of 4°. The optical performances remain stable when the pupil diameter changes from 2.25 mm to 5 mm. Besides, the presented theoretical analyses show the designed IOL has good optical performances for polychromatic light and corneal asphericity. The above shows that the IOL exhibits an excellent ability for pseudophakic eyes to see the object in a continuous range of distance.

Circadian Regulation of the Rod Contribution to Mesopic Vision in Mice.

At intermediate (mesopic) light levels, rods and cones are both active and can contribute to vision. This presents a challenge to the retina because the visual responses originating with rods and cones are distinct, yet their visual responses must be seamlessly combined. The current study aimed to establish how the circadian clock regulates rod and/or cone vision in these conditions, given the strong time-of-day change in the reliance on each photoreceptor. Visual responses were recorded in the retina and visual thalamus of anaesthetized male mice at distinct circadian time points, and the method of receptor silent substitution was used to selectively stimulate different photoreceptor types. With stimuli designed to only activate rods, responses in the mesopic range were highly rhythmic and peaked in amplitude in the subjective night. This rhythm was abolished following intravitreal injection of the gap junction blocker meclofenamic acid, consistent with a circadian variation in the strength of electrical coupling of photoreceptors. In contrast, responses to stimuli designed to only activate cones were arrhythmic within the mesopic to photopic range when adapted to the background irradiance. The outcome was that combined rod-plus-cone responses showed a stable contrast-response relationship across mesopic-photopic backgrounds in the circadian day, whereas at night, responses were significantly amplified at lower light levels. These data support the idea that the circadian clock is a key regulator of vision, in this case defining the relative amplitude of rod/cone vision across the mesopic transition according to time of day.SIGNIFICANCE STATEMENT Although the importance of circadian clocks in regulating vision has been long recognized, less is known about how the clock shapes vision in conditions where both rods and cones are active (mesopic conditions). Here, the novel approach of receptor silent substitution has been applied to trace rod and cone visual responses in mice across the circadian cycle and has identified pronounced rhythms in rod, but not cone, vision. This has the effect of boosting responses in dimmer backgrounds at night at the cost of impaired contrast-response stability across the mesopic to photopic range. Thus, the circadian clock drives anticipatory changes in the relative contribution of rods versus cones to vision, which match the prevailing visual environment.

Sensory and Motor Visual Functions in Parkinson’s Disease with Respect to Freezing of Gait Symptoms

Freezing of gait (FOG) is considered to be a motor disorder symptom that affects some Parkinson Disease (PD) patients; however, it is hypothesized that sensory systems may also be involved in FOG. This review article summarizes the results from previous studies focusing on visual functions in PD patients. More emphasize will be focused on freezing of gait PD patients and whether visual functions are affected to greater amount among them than non-freezing of gait PD patients. Visual functions include high contrast visual acuity, low contrast visual acuity, contrast sensitivity, Vernier acuity, mesopic vision, stereopsis, motion perception, and vergence eye movements are all affected in PD patients, with FOG patients having more deficits in some of these functions. FOG patients also had larger impairments in non-dopaminergic mediated functions such as pupil light reflex and visual processing speed test, which suggests that FOG patients have greater impairment in two functions that involve cholinergic neurotransmitters. Whether these impairments are contributing to the FOG or just associated with FOG is uncertain.

Colour Difference Formula for Photopic and Mesopic Vision Incorporating Cone and Rod Responses

The standard colour difference formulas, such as CIEDE2000, operate on colours defined by cone-fundamentals, which ignore the influence of rods on colour perception. In this work, we combine the rod intrusion model by Cao et al. with the popular CIEDE2000 colour difference formula and validate the accuracy of the new formula on three contrast sensitivity datasets. When compared with the standard CIEDE2000 formula, the new colour difference formula improves the perceptual uniformity of the space at low luminance levels.

Ultra‐Sensitive and Low‐Power‐Consumption Organic Phototransistor Enables Nighttime Illumination Perception for Bionic Mesopic Vision

AbstractEmulating human vision using solid‐state devices is critical in the fields of robotics, artificial intelligence, and visual prostheses, driving intense research interest. However, bionic vision devices made from routine structures suffer from low light‐perception sensitivity to nighttime low illuminations and high power consumption, impeding their applications in many advanced scenarios from nighttime autopilot to night vision neuroprosthesis. Here, an ultrasensitive and low‐power‐consumption organic phototransistor that consists of a unique Schottky‐barrier structure and separated light absorption and carrier transport layers is reported. This device design shuns the introduction of trap states into the carrier transport route, which guarantees an ultra‐steep subthreshold swing and thus significantly amplifies the photocurrent while lowering operation voltage. In consequence, the weak‐light detection capacity for this device is enhanced dramatically, which can perceive nighttime low light illuminations with ultrahigh light‐perception sensitivity of 102–104 and low power consumption of &lt;10 nW. Leveraging these findings, it is demonstrated that the phototransistor has neuromorphic vision perception behaviors and energy efficiency like human brain under faint light, opening a new opportunity for artificial vision.

照明光源の分光分布が薄明視下での色の見えに与える影響の定量的評価と色認識特性のモデル化

照明光源の分光分布が薄明視下での色の見えに与える影響の定量的評価と色認識特性のモデル化

The Blue Light Hazard Versus Blue Light Hype

The blue light hazard is the experimental finding that blue light is highly toxic to the retina (photic retinopathy), in brief abnormally intense exposures, including sungazing or vitreoretinal endoillumination. This term has been misused commercially to suggest, falsely, that ambient environmental light exposure causes phototoxicity to the retina, leading to age-related macular degeneration (AMD). We analyze clinical, epidemiologic, and biophysical data regarding blue-filtering optical chromophores. Perspective. Analysis and integration of data regarding the blue light hazard and blue-blocking filters in ophthalmology and related disciplines. Large epidemiologic studies show that blue-blocking intraocular lenses (IOLs) do not decrease AMD risk or progression. Blue-filtering lenses cannot reduce disability glare because image and glare illumination are decreased in the same proportion. Blue light essential for optimal rod and retinal ganglion photoreception is decreased by progressive age-related crystalline lens yellowing, pupillary miosis, and rod and retinal ganglion photoreceptor degeneration. Healthful daily environmental blue light exposure decreases in older adults, especially women. Blue light is important in dim environments where inadequate illumination increases risk of falls and associated morbidities. The blue light hazard is misused as a marketing stratagem to alarm people into using spectacles and IOLs that restrict blue light. Blue light loss is permanent for pseudophakes with blue-blocking IOLs. Blue light hazard misrepresentation flourishes despite absence of proof that environmental light exposure or cataract surgery causes AMD or that IOL chromophores provide clinical protection. Blue-filtering chromophores suppress blue light critical for good mental and physical health and for optimal scotopic and mesopic vision.

Dysphotopsia and functional quality of vision after implantation of an intraocular lens with a 7.0 mm optic and plate haptic design.

To determine the impact of an intraocular lens (IOL) with a 7.0 mm optic and plate haptic design on incidence of dysphotopsia and visual functions after cataract surgery. Day-care clinic. Prospective monocentric randomized patient-blinded comparative clinical study. Following preoperative measurements, patients underwent cataract surgery with implantation of 2 IOL designs-with 7.0 mm optic and plate haptics (Group 1) or with 6.0 mm optic and C-loop haptics (Group 2). In month 1, 3, and 12 follow-ups, patients were examined, answered a questionnaire regarding satisfaction, spectacle dependence, frequency, and extent of positive and negative dysphotopsia, and underwent contrast sensitivity (CS), mesopic vision, and glare sensitivity testing. The data were analyzed as nominal, ordinal, and metric with chi-square, Mann-Whitney U, Wilcoxon, and t tests. Out of a total number of 120 eyes (86 patients), Group 1 comprised 57 eyes (43 patients), Group 2 comprised 63 eyes (43 patients). Corrected distance visual acuity was the same between groups throughout the study. Group 1 showed significantly lower incidence of positive and negative dysphotopsia in month 1 follow-up (P = .021 and .015, respectively) and a higher satisfaction rate in month 3 follow-up (P = .006). Mean CS and mesopic vision with and without glare were the same in both groups. Positive dysphotopsia cases in month 12 follow-up revealed lower photopic CS (P = .005, .036, and 0.047, respectively), longer axial length, and greater preoperative pupil dynamics (P = .04 and .06). The IOL design with 7.0 mm optic diameter and plate haptics reduced dysphotopsia and provided good visual acuity, CS, mesopic vision with and without glare, and high patient satisfaction.

Spectral Optimization of White LED with Brightness Adjustable Based on Mesopic Vision

Spectral Optimization of White LED with Brightness Adjustable Based on Mesopic Vision

The Impact of the Spectral Radiation Environment on the Maximum Absorption Wavelengths of Human Vision and Other Species.

Since the earliest development of the eye (and vision) around 530 million years ago (Mya), it has evolved, adapting to different habitats, species, and changing environmental conditions on Earth. We argue that a radiation environment determined by the atmosphere played a determining role in the evolution of vision, specifically on the human eye, which has three vision regimes (photopic-, scotopic-, and mesopic vision) for different illumination conditions. An analysis of the irradiance spectra, reaching the shallow ocean depths, revealed that the available radiation could have determined the bandwidth of the precursor to vision systems, including human vision. We used the radiative transfer model to test the existing hypotheses on human vision. We argue that, once on the surface, the human photopic (daytime) and scotopic (night-time) vision followed different evolutionary directions, maximum total energy, and optimum information, respectively. Our analysis also suggests that solar radiation reflected from the moon had little or no influence on the evolution of scotopic vision. Our results indicate that, apart from human vision, the vision of only a few birds, rodents, and deep-sea fish are strongly correlated to the available radiation within their respective habitats.

Study on the Influence of LED Spectrum on the Visual and Nonvisual Effects in the Interior Zone of Tunnels

Judicious use of lamps is of profound significance to improve the internal traffic safety of tunnels. This study evaluated the biological effects of spectrum on human visual and nonvisual under mesopic vision category. According to the difference of human eyes’ response to the visual and nonvisual biological effects of different wavelengths of light radiation, a method of applying the mesopic visual spectral luminous efficiency curve to the assessment of nonvisual biological effects and blue light hazards is proposed. The results show that, in theory, under mesopic vision category, the spectrum with high correlation color temperature (CCT) and high color rendering index (CRI) has higher blue light content Z-value and has greater impact on human nonvisual effects and blue light radiation damage, but it can also provide higher human perception luminance. The visual effect detection experiment of driving in the interior zones of the tunnel is simulated in the laboratory, and the critical flicker frequency and reaction time are taken as physiological indexes. The results show that the spectrum with high CCT and high CRI corresponds to lower critical flicker frequency drop value and faster reaction time, which has a positive effect on improving driving safety. Therefore, this paper suggests that the LED with high CCT and high CRI (CCT = 6500 K, CRI2012 = 95) should be used in the interior zones of the tunnel with relatively short lighting section, and the CCT and CRI should be appropriately reduced in other road environments with long lighting section to reduce the impact of spectrum on nonvisual photobiology, so as to improve road traffic safety.

Adjustment of Lighting Parameters from Photopic to Mesopic Values in Outdoor Lighting Installations Strategy and Associated Evaluation of Variation in Energy Needs

The sensitivity of the human eye varies with the different lighting conditions to which it is exposed. The cone photoreceptors perceive the color and work for illuminance conditions greater than 3.00 cd/m² (photopic vision). Below 0.01 cd/m², the rods are the cells that assume this function (scotopic vision). Both types of photoreceptors work coordinately in the interval between these values (mesopic vision). Each mechanism generates a different spectral sensibility. In this work, the emission spectra of common sources in present public lighting installations are analyzed and their normative photopic values translated to the corresponding mesopic condition, which more faithfully represents the vision mechanism of our eyes in these conditions. Based on a common street urban configuration (ME6), we generated a large set of simulations to determine the ideal light point setup configuration (luminance and light point height vs. poles distance ratio) for each case of spectrum source. Finally, we analyze the derived energy variation from each design possibility. The results obtained may contribute to improving the criterion of light source selection and adapting the required regulatory values to the human eye vision process under normalized artificial street lighting condition, reaching an average energy saving of 15% and a reduction of 8% in terms of points of light required. They also offer a statistical range of energy requirements for lighting installation that can be used to generate accurate electrical designs or estimations without the necessity of defining the exact lighting configuration, which is 77.5% lower than conventional design criteria.

The Drive towards Optimization of Road Lighting Energy Consumption Based on Mesopic Vision—A Suburban Street Case Study

This paper presents the research of optimization of road lighting energy consumption by utilizing the fact of human twilight and night vision (mesopic vision) dependency on luminance level and lamp’s light spectral composition. The research was conducted for a suburban street illuminated by smart LED road luminaires with a luminous flux control system with which different luminance levels can be achieved on the road. This road is an access road leading to a town located on the outskirts of Warsaw which is the capital of Poland and a large metropolitan area. Therefore, the traffic here is quite heavy on this road in the morning and in the evening and it is very light at other times of the day. In accordance with EN 13201 standard, lighting control can be applied to illuminate this road. This paper compares energy consumption for different lighting scenarios of the road in question. In the first scenario, the road luminance is compliant with M4, M5, and M6 lighting class requirements depending on the time of the day. In the second scenario, for each M lighting class, the values of luminance levels provided by EN 13201 standard have been reduced to the values resulting from their conversion to the corresponding mesopic luminance values. The conducted research has shown that a 15% saving per year in electricity consumption on the road is possible with such a conversion. Therefore, energy efficiency of a lighting installation can be improved by matching the lighting levels provided by the standard to the mesopic vision.

The Impact of Color Rendering on Visual Fatigue in Interior Zone of Tunnel

Judicious use of lamps is of profound significance to improve the internal traffic safety of tunnels. This study evaluated the effect of LED color on human visual fatigue under mesopic vision category. According to the difference of human eyes’ response to different wavelengths of light radiation, the mesopic vision spectral luminous efficiency curve is applied to the visual fatigue evaluation methods. Taking the critical fusion frequency as the physiological index, the detection experiment of human visual fatigue was carried out in the simulated tunnel environment. The results show that spectrum with high color rendering index has a positive effect on alleviating drivers’ visual fatigue, and is more suitable for tunnel interior lighting.

Comparative Analysis of the Wave Front Aberrations and Ophthalmoergonomic Parameters after Excimer Laser and Orthokeratological Correction of Myopia in Patients over 35 Years

Purpose. Comparative analysis of the wavefront aberrations and ophthalmoergonomic parameters after excimer laser and orthokeratological correction of myopia in patients aged over 35 years.Patients and methods. The study included 21 patients: 12 (24 eyes) after excimer laser correction of myopia (group 1) and 9 (18 eyes) after orthokeratology (group 2). The average age of patients after excimer laser surgery was 38.5 years, after orthokeratological correction 46.1 years. Special studies included ophthalmoergonomical tests: far and near distance visual acuity, capacity of the visual analyzer, visual productivity, reading velocity, mesopic vision, relative accommodation reserves, objective accommodative response, pseudo-accommodation volume. Wavefront aberrations were conducted on the OPD-scan 3.Results. The spherical equivalent of residual refraction was –0.625 ± 0.08D in the excimer group, and –1.58 ± 0.24D in orthokeratological group. Despite the difference in refraction, values of distance binocular and monocular visual acuity were the same in both groups: in group 1 monocular visual acuity was 0.74 ± 0.03, binocular 0.85 ± 0.03; in group 2 — 0.71 ± 0.06 and 0.89 ± 0.05 respectively. The parameters of both monocular and binocular accommodative response measured on Grand Seiko were 50 % higher in the excimer group compared to those in the orthokeratological group. Relative accommodation reserves appeared to be two times more in the excimer group. The volume of pseudo-accommodation was 2.375 ± 0.12D in group 1, which appeared to be 20 % more than in the group 2 (p = 0.0414). The level of wavefront aberrations was significantly higher in orthokeratological group with the exception of vertical aberrations and, especially horizontal coma, which were significantly higher after excimer laser surgery. Generally, the dynamics of aberrations in both groups correlates with changes of the corneal topography.Conclusion. Excimer laser surgery with hypocorrection is more recommended for patients aged 35–40, and orthokeratological correction for patients over 45 years old.

Seizure triggered by flicker electroretinogram in a patient with no history of epilepsy

PurposeIt is well known that repetitive flash stimulation may trigger seizures in susceptible individuals. Nevertheless, reports of such incidents occurring during recording of a flash electroretinogram (ERG) are extremely rare. Here, we describe the case of a photic-induced seizure triggered during an ERG recording in the absence of a history of epilepsy or other paroxysmal events.MethodsA 14-year-old male patient presented with reduced visual acuity and impaired mesopic vision. Ophthalmological exams confirmed the patient’s complaints but were inconclusive as to the underlying pathophysiology. An ERG recording was performed, during which the 30-Hz flicker stimulus triggered a seizure.ResultsThe ERG was essentially normal, with the exception of a 7-Hz rhythm superimposed onto the flicker ERG response that was recorded when the seizure developed.ConclusionsThe present case highlights the possibility that the 30-Hz ERG flash stimulus triggers a seizure in patients with no previous paroxysmal events. Literature evidence suggests that the likelihood of such an incident could be reduced by stimulating monocularly.