Retinal Illuminance Research Articles

The relationships between mesopic light sensitivity and macular inner and outer retinal layer thicknesses in older healthy adults

AbstractPurpose: Structural and functional markers are important for the early detection of neurodegenerative diseases of the eye. This study investigates the relationships between macular layer thicknesses and mesopic light sensitivity (MLS) in older healthy eyes.Methods: Measurements were made in 38 eyes of 38 healthy individuals of mean age 67 ± 5.6 years (range 60–80 years) and good visual acuity. MLS was measured with macular integrity assessment (MAIA) microperimetry at the central 10° diameter circle. MLSs at the central subfield (1° radius) and at four regions (temporal, nasal, superior, inferior) of the parafoveal ring (3°–5° radius of eccentricity) were registered. Total, inner, and outer retinal layer (IRL and ORL) thicknesses were measured in the macular region through spectral‐domain optical coherence tomography (SD‐OCT). Relationships between MLS and the retinal thickness in the corresponding macular region were examined using forward stepwise multiple linear regression analyses.Results: ORL and IRL thickness in the inferior parafoveal ring were significant contributing factors to the inferior MLS (ORL: p < 0.0001; IRL: p = 0.0003; R2 model = 51%). Increased ORL thickness and decreased IRL thickness correlated with worse MLS. The total retinal thickness, age, sex, refractive error, axial length, retinal illuminance or visual acuity variables were not found to be significant predictors of MLS.Conclusions: ORL and IRL thicknesses predict inferior parafoveal MLS in healthy older eyes. The measurement of MLS in combination with macular layer thicknesses may be useful for detecting loss of sensitivity caused by early degenerative diseases of the retina.

Relationship between ganglion cell complex thickness and brief presentation stimuli ‐ visual acuity across foveal and parafoveal locations in healthy eyes

AbstractPurpose: Knowledge of the retinal structure ‐ visual function relationship of healthy eyes would be important to the early detection of neuropathies of the retina. This study investigated the association between brief presentation stimuli ‐ visual acuity (BPS‐VA) and the thicknesses of the retina in healthy young eyes.Methods: Photopic and high‐mesopic BPS‐VA was measured in 35 healthy eyes of 35 young subjects (24.3 ± 3.1 years) with the Acuity‐Plus test in the fovea and the parafovea (5° eccentricity) using an optotype presentation of duration 160 ms. The macular thicknesses of the central fovea, parafovea, and macular ganglion cell complex (mGCC), and the thickness of the peripapillary retinal nerve fibre layer (pRNFL) were measured by spectral‐domain optical coherence tomography (SD‐OCT). Relationships between foveal and parafoveal BPS‐VA and the retinal thickness in the corresponding region were examined after adjusting for confounding variables.Results: In photopic luminance conditions, the inferior mGCC thickness was the only structural significant predictor to the foveal BPS‐VA (p = 0.007). Under high‐mesopic level, retinal illuminance and inferior mGCC thickness were contributing factors to the foveal BPS‐VA (p = 0.001). Retinal thicknesses were not predictors of parafoveal BPS‐VA at any of the light levels.Conclusions: The inferior mGCC thickness predicts foveal BPS‐VA measured at both photopic and high‐mesopic light levels in healthy eyes of young subjects.

Problems with diffractive IOLs

AbstractIn 2015, it was estimated that approximately 1.8 billion people were affected by presbyopia globally which was about 25% of the world population, and approximately 826 million people lacked proper visual correction. In the year 2030, the number of people with presbyopia is expected to be increasing to 2.1 billion people globally. two major IOL.Treatment and correction of presbyopia have become challenging with increasing demands and expectations of patients since there are no drugs or procedures that can cause perfect vision at all distances without risk. Surgical options, corneal or intraocular, are of increasing interest since they are based on most modern technologies. There are still risks of surgical complications, which are hardly reversible, and the best results are based on careful selection of patients. Moreover, good understanding of the limitation of the present technologies by patients and their trade‐off nature are very important, for example, patients who gain spectacle‐free of near or intermediate vision may experience some dysphotopsias in different lighting conditions or lose some sharpness of vision or stereopsis depending on the offered technology. Multifocal IOLs (MIOLs) can be made using refractive and diffractive surfaces or combination of both. The optical power in the refractive design decreases continuously from the center to the periphery of the lens creating an infinite number of focal points and is derived from the smooth hyperbolic shape of its optics. Thus, the performance of refractive design IOLs is dependent on pupil size and IOL centration. On the other hand, a diffractive IOL generates multifocality making use of light interference and is independent of pupil size. It incorporates a pattern consisting of a series of annular concentric grooves less than one micron in depth, which are engraved around the optical axis on either the front or the back surface of a lens (the echelette technology). One of the recent studies from Japan reported that patients implanted with diffractive multifocal IOLs had notable declines in the corrected distance visual acuity, distance corrected near VA, and near area of focus with aging.When compared to monofocal IOLs, MIOLs will always be related with poorer quality of vision. Moreover, good understanding of the limitation of the present technologies by patients and their trade‐off nature are very important, for example, patients who gain spectacle‐free of near or intermediate vision may experience some dysphotopsias in different lighting conditions or lose some sharpness of vision or stereopsis depending on the offered technology. Halos, glare, reduced contrast sensitivity or reduced retinal illumination are relatively common problems with MIOLs. Halos depend on the intensity and size of the out‐of‐focus image corresponding to the other foci produced by the lens, that is secondary to add power and energy distribution among foci. Moreover, if aberrations are used in their design, their position and centering might be crucial. MIOLs do not replicate the natural condition, thus patients with MIOLs must learn and adapt to their use with so called binocular neuro‐adaptation.

A five-primary Maxwellian-view display for independent control of melanopsin, rhodopsin, and three-cone opsins on a fine spatial scale.

Independent spatiotemporal control of the stimulation of the five photoreceptor classes requires a display with as many primary lights to probe their isolated spatial and temporal responses. No such system exists with suitable performance properties. We present a system to construct a five-primary display from commercially available three-primary digital light processing projectors. It optimizes the set of five primary lights required to maximize the achievable contrast of a single photoreceptor class in a silent substitution protocol, including where the background chromaticity is first specified. From these chosen five primaries, we describe a method to convert complex three-primary (RGB) images to five-primary representations with complete specification of the photoreceptor excitations at each pixel. Key to enabling this multiple display system with a single HDMI connection is a novel control protocol implemented in a deterministic field-programmable gate array controller that splits the data into five video streams to allow nearly synchronous presentation of primary image data through multiple displays. Each pixel is controlled over 9.5 bits for each primary over a single frame for measurement of threshold-level vision. In addition to a large contrast gamut, the Maxwellian view offers high retinal illumination to support the investigation of five opsin-based responses to complex spatiotemporal images with a truly silent substitution protocol, while avoiding the confounding effects of uncontrolled photoreceptor excitations as occurs in four-primary systems. The customizable primaries facilitate this display translation to species with different photoreceptor spectral responses, and the optics are designed for integration into microscopes for use as a stimulus generator in physiological experiments.

Selected ocular dimensions of three penguin species

Penguins (Spheniscidae) are a diverse clade of flightless, marine birds. Their eyes, likely a primary driver of behaviour, have been noted to have anatomic adaptations to their amphibious lifestyle. In particular, they have a relatively flat cornea, which would make the transition from a subaerial to a submarine environment require less accommodative effort. However, the ocular dimensions are not known for many penguin species, despite the diversity within the family, and their accommodative abilities have been the source of some dispute. In this study we undertook to establish the basic dimensions of the eye of the smallest, a mid-sized penguin and the second largest penguin. The power of the front surface of the cornea was inversely related to the size of both the eye and penguin, being 41.3 D in the little penguin (Eudyptula minor), a power greater than previously measured in any other penguin species, 26.3 D in the gentoo (Pygoscelis papua) and 19.1 D in the king penguin (Aptenodytes patagonicus). All other dimensions increased or decreased in line with the size of the eye. All penguins were able to achieve emmetropia in air. The gentoo appeared to be emmetropic underwater. A finding of central corneal thickening in some penguins may be artefactual. Calculations using the ocular dimensions demonstrated that the mean retinal illumination of an extended source of light in the little penguin eye is less than that of its larger, deeper-diving relatives.

Multimodal testing reveals subclinical neurovascular dysfunction in prediabetes, challenging the diagnostic threshold of diabetes.

To explore if novel non-invasive diagnostic technologies identify early small nerve fibre and retinal neurovascular pathology in prediabetes. Participants with normoglycaemia, prediabetes or type 2 diabetes underwent an exploratory cross-sectional analysis with optical coherence tomography angiography (OCT-A), handheld electroretinography (ERG), corneal confocal microscopy (CCM) and evaluation of electrochemical skin conductance (ESC). Seventy-five participants with normoglycaemia (n=20), prediabetes (n=29) and type 2 diabetes (n=26) were studied. Compared with normoglycaemia, mean peak ERG amplitudes of retinal responses at low (16-Td·s: 4.05 μV, 95% confidence interval [95% CI] 0.96-7.13) and high (32-Td·s: 5·20 μV, 95% CI 1.54-8.86) retinal illuminance were lower in prediabetes, as were OCT-A parafoveal vessel densities in superficial (0.051 pixels/mm2 , 95% CI 0.005-0.095) and deep (0.048 pixels/mm2 , 95% CI 0.003-0.093) retinal layers. There were no differences in CCM or ESC measurements between these two groups. Correlations between HbA1c and peak ERG amplitude at 32-Td·s (r=-0.256, p=0.028), implicit time at 32-Td·s (r=0.422, p < 0.001) and 16-Td·s (r=0.327, p=0.005), OCT parafoveal vessel density in the superficial (r=-0.238, p=0.049) and deep (r=-0.3, p=0.017) retinal layers, corneal nerve fibre length (CNFL) (r=-0.293, p=0.017), and ESC-hands (r=-0.244, p=0.035) were observed. HOMA-IR was a predictor of CNFD (β=-0.94, 95% CI -1.66 to -0.21, p=0.012) and CNBD (β=-5.02, 95% CI -10.01 to -0.05, p=0.048). The glucose threshold for the diagnosis of diabetes is based on emergent retinopathy on fundus examination. We show that both abnormal retinal neurovascular structure (OCT-A) and function (ERG) may precede retinopathy in prediabetes, which require confirmation in larger, adequately powered studies.

Effect of anatomical differences and intraocular lens design on negative dysphotopsia.

To assess the effect of ocular anatomy and intraocular lens (IOL) design on negative dysphotopsia (ND). Department of Ophthalmology, Leiden University Medical Center, Leiden, the Netherlands. Ray-tracing study based on clinical data. Ray-tracing simulations were performed to assess the effect of anatomical differences and differences in IOL design on the peripheral retinal illumination. To that end, eye models that incorporate clinically measured anatomical differences between eyes of patients with ND and eyes of pseudophakic controls were created. The anatomical differences included pupil size, pupil centration, and iris tilt. The simulations were performed with different IOL designs, including a simple biconvex IOL design and a more complex clinical IOL design with a convex-concave anterior surface. Both IOL designs were analyzed using a clear edge and a frosted edge. As ND is generally considered to be caused by a discontinuity in peripheral retinal illumination, this illumination profile was determined for each eye model and the severity of the discontinuity was compared between eye models. The peripheral retinal illumination consistently showed a more severe discontinuity in illumination with ND-specific anatomy. This difference was the least pronounced, 8%, with the frosted edge clinical IOL and the most pronounced, 18%, with the clear edge biconvex IOL. These results show that small differences in the ocular anatomy or IOL design affect the peripheral retinal illumination. Therewith, they can increase the severity of ND by up to 18%.

Retinal Pigment Epithelium in Human Donor Eyes Contains Higher Levels of Bisretinoids Including A2E in Periphery than Macula

PurposeWith age, human retinal pigment epithelium (RPE) accumulates bisretinoid fluorophores that may impact cellular function and contribute to age-related macular degeneration (AMD). Bisretinoids are comprised of a central pyridinium, dihydropyridinium, or cyclohexadiene ring. The pyridinium bisretinoid A2E has been extensively studied, and its quantity in the macula has been questioned. Age-changes and distributions of other bisretinoids are not well characterized. We measured levels of three bisretinoids and oxidized A2E in macula and periphery in human donor eyes of different ages.MethodsEyes (N = 139 donors, 61 women and 78 men, aged 40–80 years) were dissected into 8 mm diameter macular and temporal periphery punches. Using liquid chromatography – electrospray ionization – mass spectrometry (LC-ESI-MS) and an authentic synthesized standard, we quantified A2E (ng). Using LC-ESI-MS and a 50-eye-extract of A2E, we semiquantified A2E and 3 other compounds (eye extract equivalent units [EEEUs): A2-glycerophosphoethanolamine (A2GPE), dihydropyridine phosphatidyl ethanolamine (A2DHPE), and monofuranA2E (MFA2E).ResultsA2E quantities in ng and EEEUs were highly correlated (r = 0.97, P < 0.001). From 262 eyes, 5 to 9-fold higher levels were observed in the peripheral retina than in the macula for all assayed compounds. A2E, A2DHPE, and MFA2E increased with age, whereas A2GPE remained unaffected. No significant right-left or male-female differences were detected.ConclusionsSignificantly higher levels were observed in the periphery than in the macula for all assayed compounds signifying biologic differences between these regions. Levels of oxidized A2E parallel native A2E and not the distribution of retinal illuminance. Data will assist with the interpretion of clinical trial outcomes of agents targeting bisretinoid-related pathways.

Electrophysiological Assessment in Birdshot Chorioretinopathy: Flicker Electroretinograms Recorded With a Handheld Device.

PurposeThe flicker electroretinogram (ERG) is a sensitive indicator of retinal dysfunction in birdshot chorioretinopathy (BCR). We explored recordings from a handheld device in BCR, comparing these with conventional recordings in the same patients and with handheld ERGs from healthy individuals.MethodsNon-mydriatic flicker ERGs, using the handheld RETeval system (LKC Technologies), were recorded with skin electrodes at two centers. At one center (group 1), the stimuli (85 Td·s, 850 Td background) delivered retinal illuminance equivalent to international standards; at the other center (group 2), a different protocol was used (32 Td·s, no background). Patients also underwent international standard flicker ERG recordings with conventional electrodes following mydriasis. Portable ERGs from patients were also compared with those from healthy individuals.ResultsThirty-two patients with BCR (mean age ± SD, 56.4 ± 11.3 years) underwent recordings. Portable and standard ERG parameters correlated strongly (r > 0.75, P < 0.01) in both groups. Limits of agreement for peak times were tighter in group 1 (n = 21; −4.3 to +2.0 ms [right eyes], −3.9 to 1.5 ms [left eyes]) than in group 2 (n = 11; −3.4 to +6.9 ms [right eyes], −4.8 to +9.0 ms [left eyes]). Compared with healthy controls (n = 66 and n = 90 for groups 1 and 2, respectively), patients with BCR showed smaller mean amplitudes and longer peak times.ConclusionsPortable ERGs correlated strongly with conventional recordings, suggesting potential in rapid assessment of cone system function in office settings.Translational RelevanceFlicker ERGs, known to be useful in BCR, can be obtained rapidly with a portable device with skin electrodes and natural pupils.

A new approach to non-mydriatic portable fundus imaging

ABSTRACT Introduction The present study proposes a new hand-held non-mydriatic fundus camera for retinal imaging. The goal is to design a fundus camera which is equally effective in both clinical and telemedicine scenarios. Areas covered A new retinal illumination approach is proposed to address the main dilemma of the optical design, i.e. balancing efficacy with structural simplicity. This is achieved by symmetrical and co-axial placement of multiple illumination sources along the optical pathway. Each illumination source includes a white and a Near Infra-Red (NIR) LED, which are placed adjacent to each other. Hence, the camera can produce a view-finder with NIR illumination without the need for additional beam-splitters and filters. Expert Opinion The proposed design blends the structural simplicity of the ‘off-axis illumination with the wide field of view and uniform illumination of the ‘ring’ illumination. Moreover, the camera is designed to work with Android-based smartphones, which can easily be mounted and interfaced. The efficacy of the proposed camera is determined by ocular safety analysis and comparative evaluation with a table-top fundus camera. The results convincingly demonstrate the ability of the proposed camera as a primary driver of a wide-scale screening program in both clinical and remote resource constraint environments.

Influence of the Location of a Decision Cue on the Dynamics of Pupillary Light Response.

The pupils of the eyes reflexively constrict in light and dilate in dark to optimize retinal illumination. Non-visual cognitive factors, like attention, arousal, decision-making, etc., also influence pupillary light response (PLR). During passive viewing, the eccentricity of a stimulus modulates the pupillary aperture size driven by spatially weighted corneal flux density (CFD), which is the product of luminance and the area of the stimulus. Whether the scope of attention also influences PLR remains unclear. In this study, we contrasted the pupil dynamics between diffused and focused attentional conditions during decision-making, while the global CFD remained the same in the two conditions. A population of 20 healthy humans participated in a pair of forced choice tasks. They distributed attention to the peripheral decision cue in one task, and concentrated at the center in the other to select the target from four alternatives for gaze orientation. The location of this cue did not influence participants’ reaction time (RT). However, the magnitude of constriction was significantly less in the task that warranted attention to be deployed at the center than on the periphery. We observed similar pupil dynamics when participants either elicited or canceled a saccadic eye movement, which ruled out pre-saccadic obligatory attentional orientation contributing to PLR. We further addressed how the location of attentional deployment might have influenced PLR. We simulated a biomechanical model of PLR with visual stimulation of different strengths as inputs corresponding to the two attentional conditions. In this homeomorphic model, the computational characteristic of each element was derived from the physiological and/or mechanical properties of the corresponding biological element. The simulation of this model successfully mimicked the observed data. In contrast to common belief that the global ambient luminosity drives pupillary response, the results of our study suggest that the effective CFD (eCFD) determined via the luminance multiplied by the size of the stimulus at the location of deployed attention in the visual space is critical for the magnitude of pupillary constriction.

Effect of a 7.0 mm intraocular lens optic on peripheral retinal illumination with implications for negative dysphotopsia.

To use optical modeling to compare a 6.0 mm and 7.0 mm intraocular lens (IOL) optic diameters on peripheral retinal illumination with implications for negative dysphotopsia. Mayo Clinic, Rochester, Minnesota, and Simpson Optics LLC, Arlington, Texas. Model eye. Ray-tracing software was used to simulate retinal illumination from an extended light source for a pseudophakic eye with in-the-bag biconvex IOLs (refractive index [n] = 1.46 and 1.55) and a 2.5 mm pupil. Ray-tracing diagrams and simulated retina illumination profiles were compared using the 6.0 mm and 7.0 mm optic diameter IOLs. Retinal locations were scaled to relative visual angles from 70 to 110 degrees horizontally. A 7.0 mm optic (n = 1.46) expands the image field by 2.8 degrees compared with a 6.0 mm optic. High-angle input light misses a 7.0 mm optic at a larger visual angle than a 6.0 mm optic, shifting illumination of the peripheral retina by this light anteriorly by 5.6 degrees. Consequently, a region of nonilluminated peripheral nasal retina is enlarged and shifted peripherally using a 7.0 mm optic (visual angle, 86.3 to 96.3 degrees) compared with a 6.0 mm optic (visual angle, 83.5 to 90.7 degrees). Similar illumination changes were seen modeling a 1.55 n IOL. A narrow dark region in the nasal retina when using a 6.0 mm optic is changed to a broader, more peripheral dark region when using a 7.0 mm optic. An extended, more peripheral dark nasal region may make a temporal shadow less bothersome and explain lower negative dysphotopsia rates using a 7.0 mm optic.

The use of autorefractors using the image-size principle in determining on-axis and off-axis refraction. Part 1: Analysis of optical principles of autorefractors.

To study the optical principles and properties of autorefractors that use the image-size principle in which the size of the reimaged retinal image determines refraction. The retinal illumination and reimaging of the retinal image were described, as were variations in the basic system. Imaging was determined for systems in which the light source is either diverging or converging as it passes into the eye. Equations were determined to describe the dependence of refraction on the heights and angles of incoming and outgoing beams, and refraction error was determined when eye position was not correct. The fundamental refraction equation is where DE is refraction, h1 is the beam height entering the eye, and θ and α are the angles of the incoming and outgoing beams, respectively. The negative sign outside the brackets applies if the beam focuses before entering the eye, while the positive sign applies if the beam focuses after entering the eye. When light is diverging as it reaches the anterior eye, hyperopia produces greater retinal image sizes than myopia. The opposite is the case when light is converging as it reaches the anterior eye. The effect of incorrect ocular longitudinal position on the measured refraction was determined; this produced errors identical to those for vertex errors with ophthalmic lenses. For image-size principle autorefractors, simple equations describe the dependence of measured refraction on the height and angle of the instrument beam as it enters the eye and the angle of the light, reflected back from the retina, after it exits the eye. Further work will investigate the validity of such instruments for determining peripheral refraction.

A transcriptome atlas of the mouse iris at single-cell resolution defines cell types and the genomic response to pupil dilation.

The iris controls the level of retinal illumination by controlling pupil diameter. It is a site of diverse ophthalmologic diseases and it is a potential source of cells for ocular auto-transplantation. The present study provides foundational data on the mouse iris based on single nucleus RNA sequencing. More specifically, this work has (1) defined all of the major cell types in the mouse iris and ciliary body, (2) led to the discovery of two types of iris stromal cells and two types of iris sphincter cells, (3) revealed the differences in cell type-specific transcriptomes in the resting vs. dilated states, and (4) identified and validated antibody and in situ hybridization probes that can be used to visualize the major iris cell types. By immunostaining for specific iris cell types, we have observed and quantified distortions in nuclear morphology associated with iris dilation and clarified the neural crest contribution to the iris by showing that Wnt1-Cre-expressing progenitors contribute to nearly all iris cell types, whereas Sox10-Cre-expressing progenitors contribute only to stromal cells. This work should be useful as a point of reference for investigations of iris development, disease, and pharmacology, for the isolation and propagation of defined iris cell types, and for iris cell engineering and transplantation.

Smart contact lens: A promising therapeutic tool in aniridia.

The perform pre-clinical testing using optical design tools to simulate the optical quality of a smart artificial iris platform encapsulated in a scleral contact lens. These tools allow us to generate aniridia eye models and evaluate different metrics of visual quality and retinal illumination based on the aperture of the artificial iris based on liquid crystals. The OCT imaging technique was used to measure the geometry of the anterior segment in a patient with aniridia and, from these data, the eye model was generated with the Zemax optical design program and specific programs developed in Matlab. Ocular aberrations were calculated and the visual function of the anirida eye model was evaluated in three scenarios: (i) without optical correction, (ii) with correction with a commercial scleral contact lens, and (iii) with correction with an optical lens. Intelligent contact based on artificial iris. Optical quality in patients with aniridia is limited by the magnitude of high-order aberrations. Conventional scleral contact lens design accurately corrects for blur but is unable to compensate for high-order ocular aberrations, especially spherical aberrations. The artificial iris-based smart contact lens design enables virtually all high-order aberrations to be compensated with active control of the pupillary diameter (activation of liquid crystal cells based on ambient lighting). In addition to minimizing high-order aberrations, reducing the pupil size would increase the depth of focus. This article demonstrates by means of optical simulations the concept of an intelligent artificial iris platform encapsulated in a scleral contact lens and its possible application in patients with aniridia. Furthermore, it allows us to anticipate possible visual results in clinical trials with healthy patients (after application of mydriatic agents) and in patients with aniridia. The results demonstrate a better visual quality and a decrease in retinal illumination.

Spectral influence of the normal LCD, blue-shifted LCD, and OLED smartphone displays on visual fatigue: A comparative study

In this study, we investigated the influence of the light spectra of the normal LCD, blue-shifted LCD, and OLED smartphone displays on visual fatigue based on subjective and objective measurements. The illuminance of the retinal photoreceptors was calculated for the three displays to quantify the components of the light spectra. The results showed that the accumulated visual fatigue decreased for the display with lower retinal illuminances of the S-, M-, and L-cones, and ipRGCs when the luminance and CCT were the same. In addition, the display with larger retinal illuminances of the M- and L-cones induced more visual fatigue related to dry eye. Hence, a slight shift of the blue light peak toward a longer wavelength is recommended for reducing visual fatigue. Furthermore, an evaluation model of the overall visual fatigue level is proposed.

Effects of screen-based retinal light stimulation measured with a novel contrast sensitivity test.

Myopia is increasing worldwide hence it exists a pressing demand to find effective myopia control strategies. Previous studies have shown that light, spectral composition, spatial frequencies, and contrasts play a critical role in refractive development. The effects of light on multiple retinal processes include growth regulation, but also visual performance and perception. Changes in subjective visual performance can be examined by contrast sensitivity (CS). This study was conducted to investigate whether retinal light stimulation of different wavelength ranges is able to elicit changes in CS and, therefore, may be used for myopia control purposes. In total, 30 right eyes were stimulated with the light of different wavelength ranges, including dominant wavelengths of ∼480 nm, ∼530 nm, ∼630 nm and polychromatic light via a commercial liquid crystal display (LCD) screen. Stimulation was performed screen full-field and on the optic nerve head only. CS was measured before any stimulation and after each stimulation condition using a novel and time-efficient CS test. Post-stimulation CS changes were analyzed by ANOVA regarding the influencing factors spatial frequency, stimulation wavelength and stimulation location. A priorly conducted verification study on a subset of five participants compared the newly developed CS test to a validated CS test. The novel CS test exhibited good reliability of 0.94 logCS and repeatability of 0.13 logCS with a duration of 92 sec ± 17 sec. No clinically critical change between pre- and post-stimulation CS was detected (all p>0.05). However, the results showed that post-stimulation CS differed significantly at 18 cpd after stimulation with polychromatic light from short-wavelength light (p<0.0001). Location of illumination (screen full-field vs. optic nerve head) or any interactions with other factors did not reveal significant influences (all p>0.05). To summarize, a novel CS test measures the relationship between retinal light stimulation and CS. However, using retinal illumination via LCD screens to increase CS is inconclusive.

The magnitude of monocular light attenuation required to elicit the Pulfrich illusion

In the Pulfrich illusion, the depth of a moving object is misperceived due to induced retinal disparity and/or interocular velocity differences arising from differences in luminance, contrast, or spatial frequency between the two eyes. These effects have been shown to occur both for visual deficits and for optical corrections that introduce significant binocular differences between the retinal images. However, it remains unknown to what extent the illusion might arise given normal variation between the eyes, such as natural interocular variation in pupil diameter (anisocoria). To assess this, we examined the threshold interocular retinal illuminance difference required to experience illusory depth in two random-dot fields moving in opposite directions in 24 normally-sighted observers with dilated pupils. Interocular difference in retinal illuminance was induced by placing neutral density filters of different intensities before the left eye. A minority of subjects (n = 8) did not provide meaningful data on changes in the experience of illusory depth with interocular difference in retinal illuminance and four subjects showed biases >±10% from the 50% point of subjective equality in the psychometric function. For the remaining 12 participants, the retinal illuminance had to differ by approximately 40% for the depth between the planes to become visible at threshold levels. This difference was approximately constant over a range of absolute luminance levels from 10 to 80 cd/m2. Our results suggest that while motion-in-depth illusions due to interocular differences in retinal illuminance may be pronounced in certain ophthalmic diseases or following certain optical interventions, it is unlikely to be manifest as a result of normal interocular variations in retinal illuminance. Further, our results also point towards the existence of substantial individual differences in the experience of what is otherwise thought of as a readily appreciable motion-in-depth illusion.

Sleep and circadian phenotype in people without cone-mediated vision: a case series of five CNGB3 and two CNGA3 patients.

Light exposure entrains the circadian clock through the intrinsically photosensitive retinal ganglion cells, which sense light in addition to the cone and rod photoreceptors. In congenital achromatopsia (prevalence 1:30–50 000), the cone system is non-functional, resulting in severe light avoidance and photophobia at daytime light levels. How this condition affects circadian and neuroendocrine responses to light is not known. In this case series of genetically confirmed congenital achromatopsia patients (n = 7; age 30–72 years; 6 women, 1 male), we examined survey-assessed sleep/circadian phenotype, self-reported visual function, sensitivity to light and use of spectral filters that modify chronic light exposure. In all but one patient, we measured rest-activity cycles using actigraphy over 3 weeks and measured the melatonin phase angle of entrainment using the dim-light melatonin onset. Owing to their light sensitivity, congenital achromatopsia patients used filters to reduce retinal illumination. Thus, congenital achromatopsia patients experienced severely attenuated light exposure. In aggregate, we found a tendency to a late chronotype. We found regular rest-activity patterns in all patients and normal phase angles of entrainment in participants with a measurable dim-light melatonin onset. Our results reveal that a functional cone system and exposure to daytime light intensities are not necessary for regular behavioural and hormonal entrainment, even when survey-assessed sleep and circadian phenotype indicated a tendency for a late chronotype and sleep problems in our congenital achromatopsia cohort.

Lente de contacto inteligente: una prometedora herramienta terapéutica en aniridia

ObjectiveTo perform pre-clinical testing using optical design tools to simulate the optical quality of a smart artificial iris platform encapsulated in a scleral contact lens. These tools allow us to generate aniridia eye models and evaluate different metrics of visual quality and retinal illumination based on the aperture of the artificial iris based on liquid crystals. MethodThe OCT imaging technique was used to measure the geometry of the anterior segment in a patient with aniridia and, from these data, the eye model was generated with the Zemax optical design program and specific programs developed in Matlab. Ocular aberrations were calculated and the visual function of the anirida eye model was evaluated in three scenarios: (i) without optical correction, (ii) with correction with a commercial scleral contact lens, and (iii) with correction with an optical lens. intelligent contact based on artificial iris. ResultsOptical quality in patients with aniridia is limited by the magnitude of high-order aberrations. Conventional scleral contact lens design accurately corrects for blur but is unable to compensate for high-order ocular aberrations, especially spherical aberrations. The artificial iris-based smart contact lens design enables virtually all high-order aberrations to be compensated with active control of the pupillary diameter (activation of liquid crystal cells based on ambient lighting). In addition to minimizing high-order aberrations, reducing the pupil size would increase the depth of focus. ConclusionsThis article demonstrates by means of optical simulations the concept of an intelligent artificial iris platform encapsulated in a scleral contact lens and its possible application in patients with aniridia. Furthermore, it allows us to anticipate possible visual results in clinical trials with healthy patients (after application of mydriatic agents) and in patients with aniridia. The results demonstrate a better visual quality and a decrease in retinal illumination.