A tint to reduce eye-strain from fluorescent lighting? Preliminary observations

Lutein and Zeaxanthin Supplementation Improves Dynamic Visual and Cognitive Performance in Children: A Randomized, Double-Blind, Parallel, Placebo-Controlled Study

INTRODUCTION

Supplementation with dietary neuro-pigments lutein (L) and zeaxanthin (Z) has been shown to improve many aspects of visual and cognitive function in adults. In this study, we tested whether a similar intervention could improve such outcomes in preadolescent children.

METHODS

Sixty children (age range 5-12 years) were randomized in a 2:1 ratio in this double-blind, placebo-controlled clinical trial. Subjects were supplemented with gummies containing either a combination of 10 mg lutein and 2 mg zeaxanthin (LZ) or placebo for 180 days. Macular pigment optical density (MPOD) was the primary endpoint. The secondary endpoints included serum levels of L and Z, and brain-derived neurotrophic factor (BDNF), critical flicker fusion (CFF), eye strain and fatigue using visual analogue scales (VAS), Children's Sleep Habits Questionnaire-Abbreviated (CSHQ-A), and Creyos Health cognitive domains like attention, focus/concentration, episodic memory and learning, visuospatial working memory, and visuospatial processing speed. Safety was assessed throughout the study on the basis of physical examination, vital signs, clinical laboratory tests, and monitoring of adverse events.

RESULTS

The LZ group showed significant increases in MPOD at all visits post-supplementation, with significant increases as early as day 42 compared to placebo. The LZ group showed significant increases in serum lutein levels, reduced eye strain and fatigue, and improved cognitive performance (focus, episodic memory and learning, visuospatial working memory) at days 90 and 180 compared to placebo. Further, the LZ group showed significant increases in processing speed (CFF), attention, visuospatial processing, and serum Z and BDNF levels on day 180 compared to placebo. No safety concerns were observed.

CONCLUSIONS

Supplementing LZ resulted in increased MPOD levels, along with increased serum levels of L, Z, and BDNF. These changes were associated with improved visual and cognitive performances and reduction in eye strain and eye fatigue in the children receiving LZ gummies. The investigational product was safe and well tolerated.

TRIAL REGISTRATION

http://ctri.nic.in/ Identifier CTRI/2022/05/042364.

Targeting the intrinsically photosensitive retinal ganglion cell to reduce headache pain and light sensitivity in migraine: A randomized double-blind trial

Approximately 80% of patients with migraine report light sensitivity during attacks and almost half report that following headache, light sensitivity is the most bothersome symptom. Light wavelengths stimulating intrinsically photosensitive retinal ganglion cells (IPRGCs) exacerbate headache-associated light sensitivity; green light is most comfortable. We developed optical tints that block wavelengths exacerbating migraine pain and transmit wavelengths that are most comfortable. We studied patients with migraine to determine if spectacles with these tints ameliorate headache pain and light sensitivity. Randomized participants wore control lenses or lenses blocking light wavelengths that stimulate IPRGCs. Participants applied the lenses at migraine onset and recorded baseline, two- and four-hour headache pain on an 11-point scale. Primary endpoint was pain reduction at two hours following the first severe or very severe headache. Statistical tests used included mixed-effects model analysis, Mann-Whitney test, Cochran-Mantel-Haenszel test, Shapiro-Wilk test, Welch t-test. In 78 subjects, two- and four-hour pain reduction was not significantly different between groups. In post-hoc analyses of headaches with baseline pain scores ≥ 2, a mixed-effects model suggested that IPRGC lenses were associated with clinically and statistically significant reductions in two- and four-hour headache pain. In post-hoc analyses, fewer subjects wearing IPRGC lenses reported two-hour light sensitivity. Preliminary evidence suggests that optical tints engineered to reduce stimulation of IPRGCs may reduce migraine-associated pain and light sensitivity. Trial Registration: This study was registered at ClinicalTrials.gov (NCT04341298).

Differential diagnosis and theories of pathophysiology of post-traumatic photophobia: A review

BACKGROUND: Photophobia is a common sensory symptom after traumatic brain injury (TBI) that may have a grave impact on a patient’s functional independence, neurorehabilitation, and activities of daily living. Post-TBI photophobia can be difficult to treat and the majority of patients can suffer chronically up to and beyond one year after their injury. OBJECTIVES: This review evaluates the current theories of the pathophysiology of photophobia and the most-common co-morbid etiologies of light sensitivity in TBI to help guide the differential diagnosis and individualized management of post-TBI photophobia. METHODS: Primary articles were found via PubMed and Google Scholar search of key terms including “photophobia” “light sensitivity” “photosensitivity” “photo-oculodynia” “intrinsically photosensitive retinal ganglion cells” “ipRGC” and “concussion” “brain injury” “dry eye”. Due to paucity of literature papers were reviewed from 1900 to present in English. RESULTS: Recent advances in understanding the pathophysiology of photophobia in dry eye and migraine and their connection to intrinsically photosensitive retinal ganglion cells (ipRGC) have revealed complex and multifaceted trigeminovascular and trigeminoautonomic pathways underlying photophobia. Patients who suffer a TBI often have co-morbidities like dry eye and migraine that may influence the patient’s photophobia. CONCLUSION: Post-traumatic photophobia is a complex multi-disciplinary complaint that can severely impact a patient’s quality of life. Exploration of underlying etiology may allow for improved treatment and symptomatic relief for these patients beyond tinted lenses alone.

Association between Retinal Nerve Fiber Layer Thickness and Eye Fatigue

Eye fatigue is a common health problem across all age groups. Herein, we explored the correlation between eye fatigue and thickness of the retinal nerve fiber layer (NFL). Included in the NFL are intrinsically photosensitive retinal ganglion cells (ipRGCs), which are associated with trigeminal pain. This retrospective cross-sectional study included outpatients with best-corrected visual acuity above 20/30 in both eyes and without dry eye, glaucoma, or retinal disease. A total of 1981 patients were initially enrolled and 377 patients were declared as eligible for the study analysis. We tested subjects for the presence of major ocular symptoms and measured thickness of ganglion cell complex (GCC) using optical coherence tomography. A total of 377 outpatients (46.4% men, mean age of 57.1 years) were enrolled for analysis, based on the interview-reported prevalence of six eye symptom, as follows: 31.5% for eye fatigue, 19.2% for blurring, 18.6% for dryness, 15.7% for photophobia, 13.5% for irritation, and 4.6% for pain. The macular GCC was significantly thicker in subjects with eye fatigue compared to the group not reporting eye fatigue (103.8 μm versus 100.3 μm, P = 0.014). Regression analysis identified eye fatigue (P = 0.026, β=0.122, adjusted for age and sex) and dryness (P =0.024, β=0.130) as significantly correlated with the macular GCC thickness, while the full macular thickness showed no significant correlation. In conclusions, eye fatigue and dryness were positively associated with thickness of the macular GCC. Nonvisual symptoms might therefore play a role in the development of eye fatigue.

Pigmented contact lenses for managing ocular disorders

Blocking a selected wavelength range from the light spectrum can have multiple benefits. Ultra-violet (UV) radiation is detrimental to the retina, necessitating its blocking through sunglasses and contact lenses. The near-visible light also has enough energy to cause damage but, is typically not blocked by commercial lenses. Filtering light can also be useful to patients with migraines, amblyopia, and color blindness. Here, to achieve blocking, incorporation of pigments extracted from colored agro-products into contact lenses is explored. Pigment extraction from food powders including turmeric, spinach, paprika, and woad powders in ethanol is demonstrated. Lens immersion in pigment concentrated ethanol is done to facilitate swelling, allowing rapid pigment uptake. Pigment incorporation ensures the absence of visible light scattering, lens opacity, and leaching. The characterization of pigmented lenses is done through absorptivity and transmittance measurements. Degradation measurements investigate the stability of the green pigment extract from spinach powder with time. p-HEMA and silicone hydrogels loaded with >400 µg/g turmeric pigment act as class 1 UV blockers retaining >90% visible light transparency and screening >95% of the UVR spectra. Spinach, paprika, and woad powder loaded silicone lenses mitigate >20% visible light transmission from selective wavelengths finding applications in photophobia, amblyopia treatment, and color vision deficiency management.

Levels of Visual Stress in Proficient Readers: Effects of Spectral Filtering of Fluorescent Lighting on Reading Discomfort

Visual stress (VS) affects reading in 5-12% of the general population and 31-36% of children with reading disorders. Symptoms include print distortions and visual discomfort when reading, and are exacerbated by fluorescent lighting. Prior research has indicated that VS can also affect proficient readers. We therefore examined levels of visual discomfort in a group of expert readers (n = 24) under both standard and spectrally-filtered fluorescent lighting. Participants rated their awareness of six symptoms of VS under each lighting condition. Under the standard condition, 4(16.7%) of the group recorded moderate to high levels of VS. Differences in symptom levels and reading speed between conditions were analysed using the Wilcoxon Signed Rank Test. Under the filter condition, the group reported less discomfort regarding all six symptoms of VS surveyed. The differences were significant with respect to three of the symptoms (p = .029 - p < .001), with a medium effect size in all of them (r = .31 - r = .46) and total score (p = .007; r = .39). Variations in reading proficiency included significantly fewer self-corrections (p = .019) and total errors (p = .004). Here we present evidence that VS-type symptoms of reading discomfort are not confined to populations with reading difficulties and may also occur in proficient readers, and that simple adaptations to fluorescent lighting may alleviate such symptoms.

Effect of Blue Light-Reducing Eye Glasses on Critical Flicker Frequency

PURPOSE

This study aims to evaluate the effect of blocking short-wavelength light on critical flicker frequency (CFF).

DESIGN

This study is a prospective clinical study.

METHODS

Thirty-three participants (17 men and 16 women; age range, 28-39 years) were divided into 3 groups. Each group wore 1 of 3 types of lenses while performing an intensive computer task for 2 hours. To evaluate the effect of blocking short-wavelength light before and after the task, we measured the CFF and evaluated subjective questionnaires. We used the analysis of variance test to examine whether the type of lenses tested affected any of the visual fatigue-related parameters.

RESULTS

The type of lens worn significantly affected the CFF; however, answers to the subjective questionnaires did not differ significantly between the groups. Two of the 13 question items showed a statistical difference between lens transparency and increase in the CFF (lens 3 > lens 2 > lens 1).

CONCLUSIONS

The higher the blocking effect of the lens, the lower the reduction in the CFF, suggesting that blocking short-wavelength light can reduce eye fatigue.

A Prospective Genetic Marker of the Visual-Perception Disorder Meares-Irlen Syndrome

Prior investigations of scotopic sensitivity or Meares-Irlen syndrome have identified several features also found in attention deficit/hyperactivity disorder, chronic fatigue syndrome, and a subtype of dyslexia in which visual recognition is the primary deficit. In particular, anomalies in lipid metabolism, including low essential fatty acid status and decreased serum cholesterol, have been identified in all three disorders. Genetic expression of the transporter molecule apolipoprotein B-100 (APOB) has been correlated with abnormal lipid metabolism, particularly in relation to levels of cholesterol. Cholesterol esters are important carriers of essential fatty acids entering the retina. The APOB gene coding for apolipoprotein B-100 is located on the short arm of Chromosome 2, and closely neighbours a gene (DYX3) known to confer susceptibility to dyslexia. The APOB locus is also recognised as being one of the most highly polymorphic regions of the human genome, and thus provides a promising tool for genetic researchers. In this pilot study, certain allelic variants of the APOB gene were more common in participants diagnosed with Meares–Irlen syndrome than in individuals without the condition. This study appears to be a first in which a condition known to cause reading difficulties has been associated with the APOB gene.

A critical examination of perceptual and cognitive effects attributed to full-spectrum fluorescent lighting

Full-spectrum fluorescent lighting (FSFL) has been credited with causing dramatic improvements in vision, perception and cognitive performance as compared with other fluorescent lamp types. These effects are hypothesized to occur because of similarity between FSFL emissions and daylight, which is said to have evolutionary superiority over other light sources. This review, covering 1945-98, critically considers the evidence for these claims. In general, poor-quality research has resulted in an absence of simple deterministic effects that can be confidently attributed to fluorescent lamp type. Promising avenues for lighting behaviour research include investigations of cognitive mediators of lighting-behaviour relationships, and flicker rates and colour rendering effects on visual processing, appearance judgements and affect. Good lighting solutions are more complex than lamp type specification.

Scotopic sensitivity/Irlen syndrome and the use of coloured filters: a long-term placebo controlled and masked study of reading achievement and perception of ability

This study investigated the effects of using coloured filters on reading speed, accuracy, and comprehension as well as on perception of academic ability. A double-masked, placebo-controlled crossover design was used, with subjects being assessed over a period of 20 mo. There were three treatment groups (Placebo filters, Blue filters, and Optimal filters) involving 113 subjects with "reading difficulties", ranging in age from 9.2 yr. to 13.1 yr. and with an average discrepancy between chronological age and reading age of 1.8 yr. The 35 controls (who did not use coloured filters) ranged in age from 9.4 yr. to 12.9 yr., with an average discrepancy between chronological age and reading age of 2.1 yr. The treatment groups increased at a significantly greater rate than the control group in reading accuracy and reading comprehension but not for speed of reading. For self-reported perception of academic ability, two of the three treatment groups showed significantly greater increases than the control group. The larger improvements for treatment groups in reading comprehension may be related to a reduction in print and background distortions allowing attention to be directed to the processing of continuous text rather than to the identification of individual words. A reduction in print distortion, however, may not be sufficient to generate improved word-identification skills without additional remedial support, and this may be indicated by the nonsignificant increase in rate of reading.

Scotopic sensitivity/Irlen syndrome and the use of coloured filters: a long-term placebo-controlled study of reading strategies using analysis of miscue

This study investigated the long-term effects of using coloured filters on the frequency and type of errors in oral reading. A double-masked, placebo-controlled crossover experimental design was used, with subjects being assessed over a period of 20 months. There were three experimental groups (Placebo tints, Blue tints, and Diagnosed tints) involving 113 subjects with reading difficulties, ranging in age from 9.2 yr. to 13.1 yr. The 35 controls (ranging in age from 9.4 yr. to 12.9 yr.) had reading difficulties but did not require coloured filters. There was a significant improvement for all groups in the accuracy of miscues over the period, although experimental groups over-all did not improve at a significantly different rate than the control group. The failure to find significantly greater improvement for the experimental groups over the control group for the total period, despite subjects' reports of improved print clarity, may be partly related to the lack of effective letter-sound analysis and synthesis skills and to the use of a word-identification strategy of guessing based on partial visual analysis.

The familial incidence of symptoms of Scotopic Sensitivity/Irlen syndrome

The familial incidence of Scotopic Sensitivity/Irlen Syndrome was investigated using parents of 751 children identified with symptoms. Children were identified by methods independent of their parents' symptoms or lack of symptoms. For these children, there was an 84% chance of either one or both parents showing similar symptoms, with similar numbers of mothers identified with symptoms as fathers. The data suggest that Scotopic Sensitivity/Irlen Syndrome may be a genetically based deficit in visual processing, but the simplest genetic models do not appear to fit.

Irlen filters and reading strategies: effect of coloured filters on reading achievement, specific reading strategies, and perception of ability

The effect of tinted nonoptical (Irlen) lenses was investigated with 29 lens-using subjects and a control group of 31 subjects. Assessment of reading four months after the initial screening showed a significant improvement in reading rate and comprehension but not in accuracy. A significant decrease in the number of pauses while reading was also noted for the lens users as well as increases in correlation between word repetition and reading rate and accuracy. The lens users also showed significantly improved scores on a scale of attitude towards school tasks.