Toward U.N. Sustainable Development Goals through Global Improvement of Eye Health Services

Article: Improving eye health essential to achieving Sustainable Development Goals
Source: London School of Hygiene & Tropical Medicine (U.K.)
Published: February 25, 2022

In 2015, United Nations member states agreed to seventeen Sustainable Development Goals (SDGs) with broad objectives ranging from from health and education to economic development and environmental stewardship, committing to working toward achieving those goals by 2030. A scoping review conducted by Lancet Global Health  Commission on Global Eye Health looked at 226 studies pertaining to the relationship between eye health services and the SDGs, as mentioned in the study abstracts. Of these, 29 studies were identified as showing a relationship between direct benefits of eye health services and one or more of seven SDGs addressing poverty (SDGs 1, 2, and 8), education (SDG 4), equality (SDGs 5 and 10), and sustainable cities (SDG 11). Among eye health services studied (e.g., cataract surgery, free cataract screening, provision of spectacles, trichiasis surgery, rehabilitation services, and rural community eye health volunteers), cataract surgery and glasses had the largest number of studies that reported a benefit, all the more pertinent in that these interventions easily restore visual acuity rather than merely delay visual deterioration. The study authors highlight that as vision is the primary sense that people rely on to live, work, and contribute to society, indirect effects of improving eye health services likely extend to all other SDGs, in turn affecting not only individuals, but also communities and countries as a whole. Despite undeniable importance, to the point that it is taken for granted until vision is threatened, attention to eye health is often overlooked in the broader context of health care services. Yet, as a representative of the United Nations proffers, "No one should have to live with avoidable blindness or addressable visual impairment in the 21st century when we have proven low-cost solutions to address these conditions. The SDGs represent the highest ambition of the global community, and it is time that eye health is recognised as integral part of that." Studies such as this that highlight the importance of eye health in the context of the U.N. Sustainable Development Goals are noteworthy in bringing attention to unified goals that have potential to benefit hundreds of millions of people across the globe.

Solid green arrows indicate relationships with direct evidence of a beneficial effect, black arrows
represent likely indirect effects, and dashed green arrows represent hypothesized beneficial effects

My rating of this study: ⭐⭐⭐⭐⭐

Zhang JH, Ramke J, Jan C, et al. "Advancing the Sustainable Development Goals through improving eye health: a scoping review." The Lancet Planetary Health.  6(3):E270-E280. 24 February 2022.
https://doi.org/10.1016/S2542-5196(21)00351-X

Smart CTL Phototherapy for Diabetic Retinopathy

Article: Smart LED Contact Lenses for Treating Diabetic Retinopathy
Source: Pohang University of Science & Technology (Korea)
Published: February 23, 2022

Photos of the smart LED contact lens (left and center) and schematic of diabetic retinopathy phototherapy (right)

Diabetic retinopathy is the most frequent complication caused by diabetes and the most common cause of blindness in the working-age population in industrialized nations. In the oxygen-scarce environment of the diabetic retina, aberrant new blood vessels form (neovascularization) in an attempt to bring oxygen to the tissue. Current treatments for proliferative diabetic retinopathy include photocoagulation (which sacrifices some peripheral vision to preserve central vision) and repeat intravitreal injection of anti-vascular endothelial growth factor (anti-VEGF) or corticosteroid. A recent line of research is exploring the use of photobiomodulation with low-intensity near-infrared light to bring gentler benefits to tissue injury. Thus far, this research has been conducted in animal and cell culture models. Investigators in South Korea are advancing the delivery of this approach through the design of wireless smart LED contact lenses. They describe the design of the device as "[a] far red/NIR light emitting diode (LED) is connected with an application-specific integrated circuit chip, wireless power, and communication systems on a PET film, which is embedded in a silicone elastomer contact lens by thermal crosslinking."

Corneal safety assessment via fluorescein staining showing slight fluroescence at 320 µW, but no staining at 120 µW

As a continuation of earlier studies, the authors tested additional settings for the device, in this case having the LED of the contact lens emit 120 µW far red/NIR light to the retina. They report that administration of the far red/NIR light in 15-minute sessions three times a week for eight weeks in a rabbit model statistically significantly reduced retinal vascular hyper-permeability (leaky blood vessels) induced by diabetic retinopathy. As the LED and circuitry generate heat, safety evaluation of corneal damage was also previously assessed. The investigators report no fluorescein staining on corneas that received 40, 80, and 160 µW of light; however, slight green fluorescence was seen at 320 µW. Corneal thickness, a marker of inflammation, did not change, nor did tear volume. Finally, immunohistochemical analysis of various biomarkers of diabetic retinopathy⁠—e.g., C3 for inflammation; COX2, ICAM1, and VEGF for angiogenesis; vimentin and GFAP for cellular stress—were also assessed and showed significant reduction in eyes treated with phototherapy. Studies in safety and efficacy continue. The authors state, "Although the intervention mechanism of diabetic retinopathy by using far red/NIR light requires further research, this study is of great significance as it demonstrates that smart far red/NIR contact lenses can prevent diabetic retinopathy."

My rating of this study: ⭐⭐⭐

Lee G, Jeon C, Mok JW, et al. "Smart Wireless Near-Infrared Light Emitting Contact Lens for the Treatment of Diabetic Retinopathy." Advanced Science.  29 January 2022. https://doi.org/10.1002/advs.202103254

Pathological Eating Disorders in Diabetics is Associated with Increased Risk of Diabetic Retinopathy

Article: Eating disorders linked to diabetic eye issues
Source: Anglia Ruskin University (U.K.)
Published: February 23, 2022

Diabetes mellitus is characterized by elevated glucose in the blood, which over time can lead to macrovascular and microvascular damage to organs with dense blood vessel networks, such as the kidneys, the extremities, and the retina, among other vital organs like the heart and brain. Among microvascular complications due to diabetes, diabetic retinopathy (DR) is the most frequent complication and the most common cause of blindness in the working-age population in industrialized nations. The risk of diabetic retinopathy affects all demographics of people with diabetes. Researchers in the U.K. conducted a systematic review and meta-analysis to answer the question of how pathological eating disorders, which affect insulin intake, influence the risk of diabetic retinopathy in diabetic individuals. They examined seven studies published about the subject up until early 2021; together, the studies included 1,162 participants. Two eating disorders, anorexia nervosa and bulimia nervosa contained enough data for sub-group analysis. They did not find any significant associations between DR and binge eating disorder. Of the pooled data for pathological eating disorders, the authors report that the odds ratio of diabetic retinopathy was 2.94, that is, diabetics with eating disorders were almost three times more likely to be at risk for retinopathy than diabetics in the general population. Eating orders not otherwise specified similarly yielded an odds ratio of 2.73. Lead author of the study explains, "The most likely reason for this is poor control of blood sugar levels due to inconsistent food intake or people deliberately not taking insulin as a weight management tactic." They conclude that the study brings awareness to practitioners who are monitoring people with diabetes to preclude this risk.

My rating of this study: ⭐🌸

Trott M, Driscoll R, Iraldo E, et al. "Pathological eating behaviours and risk of retinopathy in diabetes: a systematic review and meta-analysis." Journal of Diabetes & Metabolic Disorders.  21 January 2022. https://doi.org/10.1007/s40200-022-00980-x

Hybrid Perovskites & Ferroelectric Polymers for Designing Artificial Rod Photoreceptors

Article: Perovskites used to make efficient artificial retina
Source: King Abdullah University of Science and Technology (Saudi Arabia)
Published: February 23, 2022
Article: New photoreceptors could replicate our eye's sensitivity to light
Published: February 12, 2022

The capacitive photoreceptors' sensitivities to different LED illumination,
indicating tunable properties, with peak sensitivity for green-yellow light

Neuromorphic engineering is the design of electronic circuits to mimic the neuro-biological architecture found in nervous systems. Neuromorphic vision sensors, which reflect the architecture of the eye, such as the retina's photoreceptors, could inspire the design of robotic vision systems and perceptive intelligence (security) applications. Researchers in Saudi Arabia are exploring the use of a hybrid nanocomposite material with capacitive and dielectric properties to create biomimetic photoreceptors that require less energy to operate. In this case, they engineered a hybrid composite of methylammonium lead bromide perovskite (MAPbBr₃) and the terpolymer polyvinylidene fluoride trifluoroethylene-chlorofluoroethylene (PVDF-TrFE-CFE). The perovskite is a strong absorber of visible light, currently being explored in applications like solar cell research, while the ferroelectric polymer has a high dielectric constant, which is useful for efficient charging and discharging. Termed a light intensity capacitive photoreceptor (CPR), the 4 x 4 metal-insulator-metal capacitor array responded to various wavelengths of visible light when illuminated with different colored LEDs. Moreover, this CPR mimics the spectral sensitivity curve of human photopic vision, that is, with peak sensitivity for green-yellow light. Additionally, the authors report that the hybrid material is highly stable, with no degradation or change in response after storage for 129 weeks (~2.5 years) in ambient conditions. Finally, they observed that the CPR with 100 output neurons could, after unsupervised training, recognize handwritten digits with > 70% accuracy; they hypothesize that accuracy could reach 95% with a network of 1,500 neurons or if supervised deep learning algorithms were used. The team next plan to expand the size of the array, optimize interface circuitry, and improve accuracy with a multilayered neural network.

Spiking neural network processing the spike train, generated after seeing handwritten digits

My rating of this study: ⭐⭐

Vijjapu MT, Fouda ME, Agambayev A, et al. "A flexible capacitive photoreceptor for the biomimetic retina." Light: Science & Applications  11:3. 1 January 2022. https://doi.org/10.1038/s41377-021-00686-4

SARM1 as Potential Gene Target for RGC Degeneration

Article: Scientists pinpoint genetic target with promise for treating many forms of blindness
Source: Trinity College Dublin (Ireland)
Published: February 17, 2022

Sarm1 knockout mice had better optokinetic response/spatial vision
at 2 and 4 months (left graph), consistent for both sexes (right graph)

The heterogeneity of genetic diseases presents a challenge to gene therapy. However, mechanistic commonalities inspire the search for a gene-independent approach. For example, researchers note that mitochondrial dysfunction and axonal degeneration are features of many neurodegenerative diseases, including those that affect the retinal ganglion cells (RGCs) that comprise the optic nerve leading to the brain. Ocular neurodegenerative diseases of the optic nerve manifest in conditions from glaucoma to Leber hereditary optic neuropathy (LHON). In the present study, investigators in Ireland explored the neuroprotective effect of the absence of a prodegenerative NADase called sterile alpha and Toll/interleukin-1 receptor motif-containing 1 (SARM1). NAD, or nicotinamide adenine dinucleotide, is a coenzyme central to metabolism in all living cells; enzymatic breakdown of NAD in this case leads to tissue degeneration. The researchers engineered Sarm1  knockout mice and compared them with wild-type controls in a disease model of retinal ganglion cell degeneration through intravitreal injection of rotenone (a natural insecticide and herbicide derived from the roots of Lonchocarpus species). They found that compared to wild-type mice, the Sarm1^−/− mice had better outcomes after rotenone insult, including greater survival of RGCs, preservation of axonal density of optic nerves, increased oxygen consumption rate of primary fibroblasts and other measures of cellular respiration, preservation of photopic negative response (an electrophysiological measure of RGC activity), significantly higher optokinetic response, and overall protection of spatial vision sustained over time to 4 months. The authors conclude, "Collectively, our data indicate that Sarm1  ablation increases mitochondrial bioenergetics and confers histological and functional protection in vivo in the mouse retina against mitochondrial dysfunction, a hallmark of many neurodegenerative conditions including a variety of ocular disorders." 

My rating of this study: ⭐⭐⭐

Finnegan LK, Chadderton N, Kenna PF, et al. "SARM1 Ablation Is Protective and Preserves Spatial Vision in an In Vivo Mouse Model of Retinal Ganglion Cell Degeneration." International Journal of Molecular Sciences.  23(3):1606. 30 January 2022. https://doi.org/10.3390/ijms23031606

Insights into Rapid Eye Movement during Sleep

Article: Our eye movements reveal our emotions during sleep
Source: Paris Brain Institute, Sorbonne University (France)
Published: February 16, 2022

Slow eye movements were associated with positive emotions during dreaming,
while negative emotions were never associated with them

It is well-known that rapid eye movements (REMs) occur during dreaming, while the rest of the body is paralyzed during a stage of sleep called REM sleep. However, what rapid eye movement indicates is poorly understood and supporting evidence indirect. Some researchers have hypothesized that rapid eye movement follows the dream scenario, similar to how the eyes would move when awake. Others proposed that rapid eye movement is linked to reactivation of emotional memory during dreaming, and some studies have shown that rapid eye movement is more frequent in REM sleep of people suffering from or at risk of depressive disorders, suggesting an association to regulation of mood and emotions. Investigators in France studied the link between REM sleep and emotions during dreams through observations of 20 participants with REM sleep behavior disorder. In this case, the participants' emotions during dreaming are revealed in their facial expressions, speeches, or other behaviors. Senior author of the study comments, "Thanks to them, we have direct access to the emotional content of the dream." Using video and electro-oculography recordings, the researchers observed that positive behaviors were associated with slow eye movements (SEMs) (OR = 2.8) while negative behaviors increased with isolated REM activity (OR = 2.6) and especially with REM bursts (OR = 10.1). Slow eye movements were never linked with negative behaviors/emotions. Sleep behavior disorders could be considered an extreme manifestation of the more typical rapid eye movements that every one of us experiences during dreaming, and thus more easily demonstrate insights about the neurology of the general population. The researchers conclude, "These results support an association between REMs and SEMs, and dream emotions."

My rating of this study: ⭐🌸

Maranci JB, Nigam M, Masset L, et al. "Eye movement patterns correlate with overt emotional behaviours in rapid eye movement sleep." Scientific Reports. 12:1770. 2 February 2022.
https://doi.org/10.1038/s41598-022-05905-5