Utility of retinoscopy to examine peripheral refraction

Purpose: This study explored whether retinoscopy (RET) provides comparable results of relative peripheral refraction (RPR) to open–field autorefractometry (AR) in myopic subjects.Methods: Peripheral refraction was measured in 20 myopic and 20 control adult subjects. Both central and peripheral refraction (20° nasal and temporal eccentricity) were measured using RET and open-field AR. Differences in the median central spherical equivalent (SE), median RPR, and median J45/J180 power vectors between the RET and AR techniques were analyzed. Moreover, Bland – Altman plots were used to assess the agreement between RET and AR methods for RPR measurements in MG. Results: For MG, the median RPR values were positive (hyperopic shift), and no significant differences were observed between the RET and AR techniques with respect to RPR measurement. In addition, we did not observe any significant differences in the RPR values between the nasal and temporal eccentricities for either the RET or AR technique for myopic subjects. There was also a significant correlation and agreement between the RET and AR technique for RPR measurements. With respect to central refraction, the median SE was slightly more positive for the RET than for the AR technique. Inside the CG, we also found significant correlation between the RET and AR technique for RPR measurements, and we observed a myopic shift in peripheral eccentricities. Conclusion: Our results show that retinoscopy may be a useful tool for objective measurements of RPR in myopic subjects and may be used interchangeably with the open-field AR method in everyday clinical practice. (AU)

Red and green defocus curves and duochrome test in different age groups / Curvas de desenfoque rojo y verde y prueba de duocromo en diferentes grupos de edad

Purpose: To compare the eye defocus curves (DCs) obtained with stimuli on red, green, and white backgrounds and to investigate the applicability of the duochrome test (DT) in different age groups. Methods: 12 elderly (ELD: 59.3 ± 3.9 years) and 8 young (YG: 22.1 ± 1.1 years) subjects were recruited. An optometric assessment with the DT was carried out to obtain the subjective refraction at distance. DCs at distance on green, white, and red backgrounds were measured and the following parameters were deduced: dioptric difference between red-green, green-white, red-white focal positions (minima of the DCs), best corrected visual acuity (BCVA), and widths of the DCs for red, green, and white. Results: The DC difference between the green-white focal positions (mean ± standard deviation) was -0.12±0.17 diopters (D) (ELD, p = 0.012) and -0.11±0.12 D (YG, p = 0.039), while the red-white difference was not statistically significant. The DC red-green difference was 0.20±0.16 D (ELD, p = 0.002) and 0.18±0.18 D (YG, p = 0.008). The ELD BCVA with green background was significantly worse than BCVA with red (p = 0.007) and white (p = 0.007). The mean value of the DC's width in ELD for green (1.01±0.36 D) was higher than for red (0.77±0.21 D) and for white (0.84±0.35 D), but with no statistical significance. Conclusion: Both age groups showed a slight focusing preference for red when using white light. Moreover, ELD showed a worse BCVA with a green compared to a red background. Despite these results deduced by DC analyses, these aspects do not compromise the possibility of using the DT in clinical practice both in the young and in the elderly. Furthermore, the difference of about 0.20 D between red-green DC in both groups confirms the clinical appropriateness of the widespread use of 0.25 D step as the standard minimum difference in power between correcting lenses.(AU)

Assessing the role of visual dysfunctions in the association between visual symptomatology and the use of digital devices / Evaluación del papel de las disfunciones visuales en la asociación entre la sintomatología visual y el uso de dispositivos digitales

Purpose: To evaluate the association between visual symptoms and use of digital devices considering the presence of visual dysfunctions. Methods: An optometric examination was conducted in a clinical sample of 346 patients to diagnose any type of visual anomaly. Visual symptoms were collected using the validated SQVD questionnaire. A threshold of 6 hours per day was used to quantify the effects of digital device usage and patients were divided into two groups: under and above of 35 years old. A multivariate logistic regression was employed to investigate the association between digital device use and symptoms, with visual dysfunctions considered as a confounding variable. Crude and the adjusted odds ratio (OR) were calculated for each variable. Results: 57.02 % of the subjects reported visual symptoms, and 65.02% exhibited some form of visual dysfunction. For patients under 35 years old, an association was found between having visual symptoms and digital device use (OR = 2.10, p = 0.01). However, after adjusting for visual dysfunctions, this association disappeared (OR = 1.44, p = 0.27) and the association was instead between symptoms and refractive dysfunction (OR = 6.52, p < 0.001), accommodative (OR = 10.47, p < 0.001), binocular (OR = 6.68, p < 0.001) and accommodative plus binocular dysfunctions (OR = 46.84, p < 0.001). Among patients over 35 years old, no association was found between symptoms and the use of digital devices (OR = 1.27, p = 0.49) but there was an association between symptoms and refractive dysfunction (OR = 3.54, p = 0.001). Conclusions: Visual symptoms are not dependent on the duration of digital device use but rather on the presence of any type of visual dysfunction: refractive, accommodative and/or binocular one, which should be diagnosed.(AU)

Study of stereopsis using a depth sensation detection platform equipped with computer vision technology (DALE3D) / Estudio de estereopsis mediante una plataforma de detección de sensaciones de profundidad equipada con tecnología de visión por ordenador (DALE3D)

Background and objectives: The invention described herein is a prototype based on computer vision technology that measures depth perception and is intended for the early examination of stereopsis. Materials and methods: The prototype (software and hardware) is a depth perception measurement system that consists on: (a) a screen showing stereoscopic models with a guide point that the subject must point to; (b) a camera capturing the distance between the screen and the subject's finger; and (c) a unit for recording, processing and storing the captured measurements. For test validation, the reproducibility and reliability of the platform were calculated by comparing results with standard stereoscopic tests. A demographic study of depth perception by subgroup analysis is shown. Subjective comparison of the different tests was carried out by means of a satisfaction survey. Results: We included 94 subjects, 25 children and 69 adults, with a mean age of 34.2 ± 18.9 years; 36.2 % were men and 63.8 % were women. The DALE3D platform obtained good repeatability with an interclass correlation coefficient (ICC) between 0.94 and 0.87, and coefficient of variation (CV) between 0.1 and 0.26. Threshold determining optimal and suboptimal results was calculated for Randot and DALE3D test. Spearman's correlation coefficient, between thresholds was not statistically significant (p value > 0.05). The test was considered more visually appealing and easier to use by the participants (90 % maximum score). Conclusions: The DALE3D platform is a potentially useful tool for measuring depth perception with optimal reproducibility rates. Its innovative design makes it a more intuitive tool for children than current stereoscopic tests. Nevertheless, further studies will be needed to assess whether the depth perception measured by the DALE3D platform is a sufficiently reliable parameter to assess stereopsis.(AU)

Refractive features and amblyopia in Duane's Retraction Syndrome: A review of the 582 patients / Características refractivas y ambliopía en el síndrome de retracción de Duane: una revisión de los 582 pacientes

Purpose: To report the visual and refractive characteristics and the prevalence of amblyopia in patients with different types of Duane's Retraction Syndrome (DRS). Method: This retrospective study was performed on hospital records of 582 DRS patients at Farabi Hospital, Iran, from 2012 to March 2022. Results: The mean age of patients was 19.4 ± 11.9 (range, 3–70) years [335 (57.6 %) females and 247 (42.4 %) males (P < .001)]. DRS type I, II, III, and IV were presented in 347 (59.6 %), 148 (25.4 %), 82 (14.1 %), and 5 (0.9 %) patients, respectively. There were 530 (91.1 %) patients with unilateral and 52 (8.9 %) with bilateral involvement. In the unilateral patients, the DRS eyes' corrected distance visual acuity (CDVA) and astigmatism were significantly worse than the Non-DRS Eyes (P < .001). The mean amount of all refractive and visual parameters in bilateral patients' right or left eyes was significantly lower than in unilateral patients' non-DRS eyes (all P < .05). Anisometropia was observed in 75(12.9 %) of the patients. Amblyopia was observed in 18.5 % (98 patients) and 36.5 % (19 patients) of unilateral and bilateral DRS patients, respectively (P < .001). In unilateral patients, amblyopia was found in 57 (16.4 %) patients with Type I, 22 (14.9 %) patients with Type II, 16 (19.5 %) patients with Type III, and 3 (60 %) patients with Type IV. Forty-four (37.6 %) of patients with amblyopia had anisometropia. Conclusion: This large-scale study indicates that DRS types differ in terms of refractive error, visual acuity, and the prevalence of amblyopia and anisometropia. Clinicians should be aware of the clinical features associated with different types of DRS.(AU)

Mean cycloplegic refractive error in emmetropic adults – The Tehran Eye Study / Error refractivo ciclopléjico medio en adultos emétropes: estudio ocular de Teherán

Purpose: In children under 20 years, refractive development targets a cycloplegic refractive error of +0.5 to +1.5D, while presbyopes over 40 years generally have non-cycloplegic errors of ≥ +1D. Some papers suggest these periods are separated by a period of myopic refractive error (i.e., ≤ –0.50D), but this remains unclear. Hence, this work investigates the mean cycloplegic refractive error in adults aged between 20 – 40 years. Methods: In 2002 a cross-sectional study with stratified cluster sampling was performed on the population of Tehran, providing cycloplegic and non-cycloplegic refractive error data for the right eyes of 3,576 participants, aged 30.6 ± 18.6 years (range: 1–86 years). After grouping these data into age groups of 5 years, the refractive error histogram of each group was fitted to a Bigaussian function. The mean of the central, emmetropized peak was used to estimate the mean refractive error without the influence of myopia. Results: The mean cycloplegic refractive error at the emmetropized peak decreased from +1.10 ± 0.11D (95 % confidence interval) to +0.50 ± 0.04D before 20 years and remains stable at that value until the age of 50 years. The non-cycloplegic refractive error also sees a stable phase at 0.00 ± 0.04D between 15 – 45 years. After 45 – 50 years both cycloplegic and non-cycloplegic refractive error become more hypermetropic over time, +1.14 ± 0.12D at 75 years. Conclusions: The cycloplegic refractive error in adults is about +0.50D between 20 – 50 years, disproving the existence of the myopic period at those ages.(AU)

The First Steps of the Visual Cycle in Human Rod and Cone Photoreceptors.

Purpose: Light detection destroys the visual pigment. Its regeneration, necessary for the recovery of light sensitivity, is accomplished through the visual cycle. Release of all-trans retinal by the light-activated visual pigment and its reduction to all-trans retinol comprise the first steps of the visual cycle. In this study, we determined the kinetics of all-trans retinol formation in human rod and cone photoreceptors. Methods: Single living rod and cone photoreceptors were isolated from the retinas of human cadaver eyes (ages 21 to 90 years). Formation of all-trans retinol was measured by imaging its outer segment fluorescence (excitation, 360 nm; emission, >420 nm). The extent of conversion of released all-trans retinal to all-trans retinol was determined by measuring the fluorescence excited by 340 and 380 nm. Measurements were repeated with photoreceptors isolated from Macaca fascicularis retinas. Experiments were carried out at 37°C. Results: We found that ∼80% to 90% of all-trans retinal released by the light-activated pigment is converted to all-trans retinol, with a rate constant of 0.24 to 0.55 min-1 in human rods and ∼1.8 min-1 in human cones. In M. fascicularis rods and cones, the rate constants were 0.38 ± 0.08 min-1 and 4.0 ± 1.1 min-1, respectively. These kinetics are several times faster than those measured in other vertebrates. Interphotoreceptor retinoid-binding protein facilitated the removal of all-trans retinol from human rods. Conclusions: The first steps of the visual cycle in human photoreceptors are several times faster than in other vertebrates and in line with the rapid recovery of light sensitivity exhibited by the human visual system.

Light Sensing beyond Vision: Focusing on a Possible Role for the FICZ/AhR Complex in Skin Optotransduction.

Although our skin is not the primary visual organ in humans, it acts as a light sensor, playing a significant role in maintaining our health and overall well-being. Thanks to the presence of a complex and sophisticated optotransduction system, the skin interacts with the visible part of the electromagnetic spectrum and with ultraviolet (UV) radiation. Following a brief overview describing the main photosensitive molecules that detect specific electromagnetic radiation and their associated cell pathways, we analyze their impact on physiological functions such as melanogenesis, immune response, circadian rhythms, and mood regulation. In this paper, we focus on 6-formylindolo[3,2-b]carbazole (FICZ), a photo oxidation derivative of the essential amino acid tryptophan (Trp). This molecule is the best endogenous agonist of the Aryl hydrocarbon Receptor (AhR), an evolutionarily conserved transcription factor, traditionally recognized as a signal transducer of both exogenous and endogenous chemical signals. Increasing evidence indicates that AhR is also involved in light sensing within the skin, primarily due to its ligand FICZ, which acts as both a chromophore and a photosensitizer. The biochemical reactions triggered by their interaction impact diverse functions and convey crucial data to our body, thus adding a piece to the complex puzzle of pathways that allow us to decode and elaborate environmental stimuli.

The Prodrug DHED Delivers 17ß-Estradiol into the Retina for Protection of Retinal Ganglion Cells and Preservation of Visual Function in an Animal Model of Glaucoma.

We report a three-pronged phenotypic evaluation of the bioprecursor prodrug 10ß,17ß-dihydroxyestra-1,4-dien-3-one (DHED) that selectively produces 17ß-estradiol (E2) in the retina after topical administration and halts glaucomatous neurodegeneration in a male rat model of the disease. Ocular hypertension (OHT) was induced by hyperosmotic saline injection into an episcleral vein of the eye. Animals received daily DHED eye drops for 12 weeks. Deterioration of visual acuity and contrast sensitivity by OHT in these animals were markedly prevented by the DHED-derived E2 with concomitant preservation of retinal ganglion cells and their axons. In addition, we utilized targeted retina proteomics and a previously established panel of proteins as preclinical biomarkers in the context of OHT-induced neurodegeneration as a characteristic process of the disease. The prodrug treatment provided retina-targeted remediation against the glaucomatous dysregulations of these surrogate endpoints without increasing circulating E2 levels. Collectively, the demonstrated significant neuroprotective effect by the DHED-derived E2 in the selected animal model of glaucoma supports the translational potential of our presented ocular neuroprotective approach owing to its inherent therapeutic safety and efficacy.

Effect of juggling expertise on pointing performance in peripheral vision.

Juggling is a very complex activity requiring motor, visual and coordination skills. Expert jugglers experience a "third eye" monitoring leftward and rightward ball zenith positions alternately, in the upper visual fields, while maintaining their gaze straight-ahead. This "third eye" reduces their motor noise (improved body stability and decrease in hand movement variability) as it avoids the numerous head and eye movements that add noise into the system and make trajectories more uncertain. Neuroimaging studies have shown that learning to juggle induces white and grey matter hypertrophy at the posterior intraparietal sulcus. Damage to this brain region leads to optic ataxia, a clinical condition characterised by peripheral pointing bias toward gaze position. We predicted that expert jugglers would, conversely, present better accuracy in a peripheral pointing task. The mean pointing accuracy of expert jugglers was better for peripheral pointing within the upper visual field, compatible with their subjective experience of the "third eye". Further analyses showed that experts exhibited much less between-subject variability than beginners, reinforcing the interpretation of a vertically asymmetrical calibration of peripheral space, characteristic of juggling and homogenous in the expert group. On the contrary, individual pointing variability did not differ between groups neither globally nor in any sector of space, showing that the reduced motor noise of experts in juggling did not transfer to pointing. It is concluded that the plasticity of the posterior intraparietal sulcus related to juggling expertise does not consist of globally improved visual-to-motor ability. It rather consists of peripheral space calibration by practicing horizontal covert shifts of the attentional spotlight within the upper visual field, between left and right ball zenith positions.

Glaucoma Rehabilitation using ElectricAI Transcranial Stimulation (GREAT)-study protocol for randomized controlled trial using combined perceptual learning and transcranial electrical stimulation for vision enhancement.

BACKGROUND: Glaucoma patients with irreversible visual field loss often experience decreased quality of life, impaired mobility, and mental health challenges. Perceptual learning (PL) and transcranial electrical stimulation (tES) have emerged as promising interventions for vision rehabilitation, showing potential in restoring residual visual functions. The Glaucoma Rehabilitation using ElectricAI Transcranial stimulation (GREAT) project aims to investigate whether combining PL and tES is more effective than using either method alone in maximizing the visual function of glaucoma patients. Additionally, the study will assess the impact of these interventions on brain neural activity, blood biomarkers, mobility, mental health, quality of life, and fear of falling. METHODS: The study employs a three-arm, double-blind, randomized, superiority-controlled design. Participants are randomly allocated in a 1:1:1 ratio to one of three groups receiving: (1) real PL and real tES, (2) real PL and sham tES, and (3) placebo PL and sham tES. Each participant undergoes 10 sessions per block (~ 1 h each), with a total of three blocks. Assessments are conducted at six time points: baseline, interim 1, interim 2, post-intervention, 1-month post-intervention, and 2-month post-intervention. The primary outcome is the mean deviation of the 24-2 visual field measured by the Humphrey visual field analyzer. Secondary outcomes include detection rate in the suprathreshold visual field, balance and gait functions, and electrophysiological and biological responses. This study also investigates changes in neurotransmitter metabolism, biomarkers, self-perceived quality of life, and psychological status before and after the intervention. DISCUSSION: The GREAT project is the first study to assess the effectiveness of PL and tES in the rehabilitation of glaucoma. Our findings will offer comprehensive assessments of the impact of these treatments on a wide range of brain and vision-related metrics including visual field, neural activity, biomarkers, mobility, mental health, fear of falling, and quality of life. TRIAL REGISTRATION: ClinicalTrials.gov NCT05874258 . Registered on May 15, 2023.

Moving from stable standing to single-limb stance or an up-on-the-toes position: The importance of vision to dynamic balance control.

Understanding the contribution vision has to dynamic balance control may help in understanding where/why loss of balance occurs during everyday locomotion. The current study determined how body-centre-of-mass (BCoM) dynamics and postural stability when moving to and holding a single-limb-stance (SS) or an up-on-the-toes (UTT) position were affected by visual occlusion. From standing on a force platform, 18 adults (mean (SD) 26.7 (4.8) years; 1.73 (0.08) m; 84.0 (22.9) kg; 7 females) completed repeated trials (x3) with and without vision in which they moved to either a SS or an UTT position (order countered-balanced), and attempted to hold that position for 2 (SS) or 5 (UTT) seconds before returning to standing. UTT trials were also repeated at a fast speed, and SS trials were repeated using both the dominant and non-dominant limb. BCoM dynamics were assessed by analysing the displacement and peak velocity of the centre-of-pressure (CoP) when moving to and from the SS and UTT positions. Balance stability was the variability in the CoP displacement/velocity when holding these positions. Results indicate that under visual occlusion, the peak CoP velocity when moving to the SS or UTT position was reduced (ES, 0.67 and 0.68, respectively), suggesting greater caution. Both the variability in the CoP displacement/velocity when holding these positions and the peak CoP velocity when returning to flat-standing increased (SS: ES, 1.0 and 0.86, respectively; UTT: ES 1.26 and 0.66, respectively), suggesting, respectively, greater instability and poorer control. The poorer control in SS trials, occurred when returning to standing from the SS position held on the non-dominant limb, and correspondingly, the reduction in SS duration when vision was occluded was greater for the non-dominant limb trails (limb-vision interaction; p = 0.042). This suggests that movements initiated/controlled by the non-dominant limb are more reliant on visual feedback than those initiated/controlled by the dominant limb.

Evolution: Decoding the adaptation of multi-eyed visual systems.

Many invertebrates possess more than two pairs of eyes - but does eye redundancy aid in ecological diversification? A new study finds varied size adaptation of different eye pairs in spiders, demonstrating how developmental modularity of multi-eyed systems effectively balances selective pressures.

Comparative genomics sheds new light on the convergent evolution of infrared vision in snakes.

Infrared vision is a highly specialized sensory system that evolved independently in three clades of snakes. Apparently, convergent evolution occurred in the transient receptor potential ankyrin 1 (TRPA1) proteins of infrared-sensing snakes. However, this gene can only explain how infrared signals are received, and not the transduction and processing of those signals. We sequenced the genome of Xenopeltis unicolor, a key outgroup species of pythons, and performed a genome-wide analysis of convergence between two clades of infrared-sensing snakes. Our results revealed pervasive molecular adaptation in pathways associated with neural development and other functions, with parallel selection on loci associated with trigeminal nerve structural organization. In addition, we found evidence of convergent amino acid substitutions in a set of genes, including TRPA1 and TRPM2. The analysis also identified convergent accelerated evolution in non-coding elements near 12 genes involved in facial nerve structural organization and optic nerve development. Thus, convergent evolution occurred across multiple dimensions of infrared vision in vipers and pythons, as well as amino acid substitutions, non-coding elements, genes and functions. These changes enabled independent groups of snakes to develop and use infrared vision.

Digest: How environmental light conditions shape the evolution of visual systems in birds.

How do varying environmental light conditions influence the evolution of avian visual systems? Fröhlich et al. (2024) demonstrate that nocturnal birds evolved broader corneas and slightly longer axial lengths than their diurnal counterparts, increasing light capture efficiency. Nocturnal species also tended to maintain or reduce the size of brain regions responsible for vision, i.e., the optic tectum and the visual wulst. These results highlight adaptive trends in nocturnal species, where evolutionary improvement in low-light performance of eyes may be accompanied by compromised brain function.

Characterizing medaka visual features using a high-throughput optomotor response assay.

Medaka fish (Oryzias latipes) is a powerful model to study genetics underlying the developmental and functional traits of the vertebrate visual system. We established a simple and high-throughput optomotor response (OMR) assay utilizing medaka larvae to study visual functions including visual acuity and contrast sensitivity. Our assay presents multiple adjustable stripes in motion to individual fish in a linear arena. For that the OMR assay employs a tablet display and the Fish Stripes software to adjust speed, width, color, and contrast of the stripes. Our results demonstrated that optomotor responses were robustly induced by black and white stripes presented from below in the linear-pool-arena. We detected robust strain specific differences in the OMR when comparing long established medaka inbred strains. We observed an interesting training effect upon the initial exposure of larvae to thick stripes, which allowed them to better respond to narrower stripes. The OMR setup and protocol presented here provide an efficient tool for quantitative phenotype mapping, addressing visual acuity, trainability of cortical neurons, color sensitivity, locomotor response, retinal regeneration and others. Our open-source setup presented here provides a crucial prerequisite for ultimately addressing the genetic basis of those processes.