News
Rhapsody in blue : a conference on the role of blue light
A conference entitled “Rhapsody in Blue” was held on 25 March 2010 in the Museum of Natural History of Geneva, Swiss. It was organized by the University Hospitals of Geneva, and chaired by Prof. Avinoam B. Safran, Head of the Department of Ophthalmology. The Conference focused on the theme “two faces of the blue” and presented the current advances in the knowledge on the blue light for ophthalmology practice. The scientific program was conceived to discuss the role of the blue light in physiological and pathophysiological pathways, including modifications of circadian rhythms and hormone secretion, sleep propensity and alertness, emotions and cognition, retinal neurophysiology and pupillary constriction. Keynote lectures were held by ten opinion leaders in the field.
For 150 years, rods and cones have been considered the only photoreceptors of the mammalian eye. Recent findings (2002) identified a novel photoreceptor with distinctive morphological and functional features, the photosensitive retinal ganglion cells (pRGC), also called intrinsically photosensitive retinal ganglion cells (ipRGC). In addition to the classical visual effects, light elicits non-visual brain responses (“inconscious visual information”), which are mediated by the photopigment melanopsin. Melanospin is most sensitive to blue light, at around 470-480 nm wavelength. The melanopsin-expressing ganglion cells transmit signals to hypothalamic nuclei such as the suprachiasmatic nuclei and to a number of nonhypothalamic brain structures, e.g. superior colliculi, lateral geniculate nuclei and medial amygdala. Though less than 1% of the retinal ganglion cells are photoreceptive, they appear to play a key role in the physiological responses to daylight. They encode the intensity of bright environmental illumination, set the biological clock, control the synthesis of melatonin, adjust the pupil diameter and regulate the emotion-cognitive sphere.
Dr Aki Kawasaki’s talk (Lausanne) was focused on the melanopsin-expressing retinal ganglion cells and their sensitivity to blue light. She underlined the fact that these cells are highly conserved during the evolution and have essential role in surviving of the species. In retinitis pigmentosa, up to 90% of the ganglion cells are preserved, while the rod and cone cells are severely damaged. In Leber’s hereditary optic neuropathy, patients lose their vision but have a preserved pupil reflex. The pupil light reflex obtained from blue light stimulation is driven by melanopsin. It was suggested that chromatic pupilometry may become a screening test and alternative diagnostic method for retinal degenerative disorders.
New imaging techniques of the retina and their diagnostic implications were reviewed by Dr Guy Donati (Geneva). Dr François Majo (Lausanne) presented the use of blue in the eye color surgery.
Prof. José-Alain Sahel (Paris /London) devoted his lecture to the mechanisms underlying the retinotoxicity of the blue light. He revealed the role of different factors modulating in direct and cumulative manner the sensibility of the retina to the phototoxic effects of the blue light, including oxidative stress and age. The human retina is protected from shorter wavelength radiation by the cornea and lens that absorb UV light below 295 and 400 nm respectively. It is recognized now that light, particularly blue light, can interact with the retinal pigment epithelial-associated photosensitizers lipofuscin and melanin and the photoreceptor-associated photosensitizers opsins and retinoids to cause cellular damage via generation of reactive oxygen species (ROS). The role of potential protective factors was also highlighted.
Dr A. Roth (Geneva) gave a talk on the possible side effects of the “blue pill” Viagra® (sildenafil) such as impaired light and color perception (cyanopsy) and acute ischemic optic neuropathy.
Critical steps toward development of high technologies to limit unwanted risks of the blue light exposure were presented by T. Villette, Head of the research and development neuro-bio-sensorial department of Essilor, Paris.
New horizons in understanding the chronobiology mechanisms were discussed by Dr M. Munch (Lausanne). Light was evoked as most important synchronizer of the biological rhythms. Non-visual/non-image forming system responds to bright properly timed light exposures to assure effective circadian rhythm and optimal diurnal physiological processes. Inadequate environmental light can cause circadian disruption, increasing the risk of insomnia, depression and numerous systemic disorders. Artificial lighting is dimmer and less blue-weighted than natural daylight, contributing to age-related losses in unconscious circadian photoreception. Aging itself reduces crystalline lens light transmission, especially of short wavelengths, and decreases pupil area resulting in progressive loss of circadian photoreception. If retinal ganglion cell photoreceptors and their suprachiasmatic connections are intact however, circadian photoreception persists even in visually blind individuals. This is why visually blind patients should be encouraged to get sufficient light.
Environmental illumination is inversely correlated with insomnia and depression, both of which increase with aging. The link between light and depression were emphasized by Dr J. M. Aubry (Lausanne) as a possible target for developing of therapeutic strategies for seasonal affective disorders (SAD), which affect approximately 10% of the population during the fall and winter. Bright light, particularly from bluer sources such as outdoor daylight, can reduce or eliminate insomnia and depression, and normalize circadian hormonal amplitudes, mood, alertness and cognitive function.
Considerations on visual neuroscience and neuropsychiatry issues through the blue shadows in the paintings and the blue color in master pieces of Claude Monet and Picasso were evoked by Prof. P. Lanthony (Paris) and Prof. A. Safran. Special attention was paid to the significant impact of the blue color in expressing a mental state of depression. Close association between blue, blindness and depression was clearly indicated.
The Conference offered an excellent opportunity to communicate scientific information and afforded evidence of fruitful cooperation between ophthalmologists, neurobiologists and psychiatrists, and opened new horizons in continued postgraduate education and professional development.
To consulte the conference’s program: click here
The Rare Disease Day 2010
The last day of February has been officially designated as International Rare Disease Day. Besides the patient organisations, government representatives and policy makers, medical professionals and academia, researchers and pharmaceutical industry participate in an array of events designed to raise awareness for the rare disease cause. This year’s theme is “Patients and researchers, partners for life!”
For the first time in 1999, the European Commission adopted a Community action program to ensure a high level of health protection and better understanding of rare diseases. A disease is defined as rare when it affects less than 1 in 2000 individuals in the general population. Rare diseases are now one of the priorities in the Community action program in the field of health to support member states in diagnosing, treating and caring for the 36 million EU citizens with rare diseases (Council Recommendation on a European Action in the field of Rare Diseases, Luxembourg, 9 June 2009).
It is estimated that there are 6000 to 8000 rare diseases and approximately 80% of them are genetic. Genetic eye diseases include a large number of ocular pathologies and nearly 500 contributing genes and specific mutations within over 150 of these genes have been identified so far. Rare eye disorders have a significant health impact as more than 60% of childhood cases of blindness are due to congenital cataracts and glaucoma, retinal degenerations, optic atrophy, and eye malformations. Among the group of retinal degenerations, retinitis pigmentosa affects approximately 1 in 3,000-5,000 individuals and is responsible for visual loss of 1.5 million people worldwide. Usher syndrome (a deaf–blindness condition) affects one child in 20,000-25,000. Retinoblastoma, a rare embryonic neoplasm of retinal origin (1:20,000 live births), is the most common intraocular malignancy in children. In adults, glaucoma and age-related macular degeneration are among the leading causes of blindness, and both appear to be inherited in majority of cases. It is estimated that eye abnormalities are present in one-third of the rare systemic diseases (e.g. Marfan’s syndrome, neurofibromatosis, oculocutaneous albinism, Stickler syndrome, CHARGE syndrome) which means that about 1800 syndromes involve eye disease as a component. Thus genetic eye diseases, though considered to be rare, represent a critical public health issue and are also among the WHO priority diseases.
After the First Rare Disease Day (February 29, 2008), the International Rare Disease Day this year will take place on February 28 to highlight the research on rare disease and to boost successful partnerships between patients and researchers. Research undoubtedly represents a hope for the millions of rare disease patients who are without cure today.
The Vision Institute was created in 2008 with the support of INSERM, CNRS, University Pierre and Marie Curie (UPMC) and Centre Hospitalier National d’Ophtalmologie (CHNO) des Quinze-Vingts as one of the first European research centers for eye diseases and the only French center exclusively dedicated to eye pathologies. The Center of Clinical Investigations (CIC) at the CHNO offers a platform for innovative studies and for the National Reference Center of Rare Retinal Diseases. It is also part of EVI.CT.SE (European Vision Institute. Clinical Trials. Sites of Excellence), the European network of excellence for clinical trials. The CIC is specialized in the research on retinal pathologies known to be a major cause of blindness. About 200 clinicians and researchers work together at the Institut de la Vision on development of new therapeutic strategies for these devastating conditions. Strong international scientific collaborations have been developed and international networks build. Technology-focused innovations and translational projects are within the mainstream of research, often conducted in partnership with industrials. Some of the priority themes currently include phenotype/genotype correlations, prevention and treatment of the neovascularization in age related macular degeneration, pathophysiology and therapeutic options in retinitis pigmentosa and diabetic retinopathy, familial forms of retinal venous occlusions and their treatment, Leber hereditary optic neuropathy, glaucoma, artificial retina. Clinical studies in progress can be consulted at: www.cicoph.org.
Research holds promise for improved medical decision making and more effective management of rare eye diseases. The Vision Institute offers strong scientific expertise and deep commitment to achieve these goals.
