Visible light and the retina
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influence of visible light on the retina
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Visible light and the retina
- 1. Visible Light and the Retina Yasuo Yanagi Associate Professor: Duke-NUS medical School Singapore National Eye Centre/ Singapore Eye Research Institute
- 2. Retina Anatomy of the eye Optic Nerve Retina Cross-section Crystalline lens Optic nerve 1. Light first enters the eyes through the cornea (a clear lens), through the iris pupil (an aperture, or hole that changes sizes), through the crystalline lens (another clear lens responsible for fine-focusing), through the clear vitreous.
- 3. Retina Anatomy of the eye Optic Nerve Retina Cross-section Crystalline lens Optic nerve 2. Light focuses onto the retina. Pigments in the retina detect an image. This generates an electrical signal, which is sent to the brain through a living electrical wire called the optic nerve.
- 4. Retina Anatomy of the eye Optic Nerve Macula Retina Macula Cross-section Crystalline lens Optic nerve Macula: the most important part of the retina. This region lies at the anatomic centre of the retina.
- 5. Retina The brain receives the signal and interprets the message, much like a computer. MaculaOptic nerve Choroid Retinal pigment epithelium Neural retina Macula: Cross section Visual cortex (striate cortex) Signal from the Macula Brodmann’s area Fovea
- 6. Exposure to visible light causes some retinal diseases • Acute phototoxicity – Solar retinopathy – Retinal damage by surgical devices (e.g. operating microscope, endoilluminator) Ham et al., Nature 1976
- 7. Solar retinopathy Potential causes: solar eclipse viewing without proper precautions religious ritual participation mental disturbances via drug intoxication or schizophrenia. Exposures lasting for several minutes to tens of minutes are sufficient to cause a damage.
- 8. Solar retinopathy very small defect that affects the outer retina Symptoms develop 1 to 4 hours by decreased vision. Macula lesion Optical Coherence Tomography Retina
- 9. Focus light Exposure to light and retinal damage Lipofuscin “photochemical damage” mediated by lipofuscin (age pigment) is related to “phototoxicity”
- 10. Acute phototoxicity is mediated by lipofuscin Yanagi Y et al., BJO 2006 *: ARPE-19 cells †: A2E Lipofuscin† laden RPE cells RPE cells* Cell viability 100% 20% Light exposure 48 hrs
- 11. wavelength (nm) Spectral absorbance of lipofuscinAbsorbance UV Visible light Blue light and retinal phototoxicy Absorbs blue light Yanagi et al., Graefe’s Arch Clin Ophthalmol 2007
- 12. Oxidative stress induced by light exposure Age related macular degeneration Light exposure⬆ Mitochondrial damage Decreased ATP Inflammation Increased secretion of inflammatory cytokines Absorbed by lipofuscin Evidence from in vitro experiments suggest that blue light at 10 W/m2 induces photochemical retinal damages (Class II) up on acute (hours) exposure.
- 13. Blue light hazard retinal damage caused by intense blue light • Blue light causing retinal lesions is based on the studies using acute intense light exposure. • Direct viewing of extremely high-brightness light (including LEDs) may cause eye damage. • It is still an open question as to whether long-term chronic exposure to blue light may cause vision problems.Typical daily activities are related with exposures of the retina to light levels well below the threshold doses causing acute photodamage to the retina.
- 14. Choronic phototoxicity – experimental results • Acute phototoxicity – Solar retinopathy – Retinal damage by surgical devices (e.g. operating microscope, endoilluminator) Ham et al., Nature 1976 • Chronic phototoxicity – Retinal damage by physiological light Lawwill et al., 1982 Trans Am Ophthalmol Soc
- 15. Chronic phototoxicy – animal models • Rodents – Noell et al., Retinal damage by light in rats Invest Ophthalmol (1966) • Primates – Lawwill et al., Retinal damage to chronic light exposure Doc Ophthalmol (1977) Retinal damage from long-term physiological light??? Modified from Lawwill et al., Intensityoflight Damage induced by chronic phototoxic reactions occurring in the retina may be involved in the etiology of debilitating ocular conditions.
- 16. Sunlight exposure and age-related macular degeneration Age-related macular degeneration is the leading cause of blindness in developed countries. The disease creates a permanent central vision blind spot.
- 17. Sunlight exposure and age-related macular degeneration • The Beaver Dam Eye Study., Sunlight and the 10-year incidence of age- related maculopathy: the Beaver Dam Study (2004) Arch Ophthalmol. – Relevance of AMD incidence / progression and sun exposure(+) • Tayler HR et al., Visible light and risk of age-related macular degeneration: (1990) Trans Am Ophthalmol Soc – There is relevance blue light exposure and AMD – No relevance to UV-exposure • Darzins P et al., Sunlight exposure and age-related macular degeneration – Sun exposure is small in AMD patients – Relevance of Ray hypersensitivity of the skin and AMD (+) • Khan JC et al., Age-related macular degeneration and sun exposure, iris colour, and skin sensitivity to sunlight (2006) Br J Ophthalmol – Relevance of AMD and sun exposure(-) – Relevance of Geographic atrophy and the light hypersensitivity(+) Sui et al., BJO 2013 Pooled OR =1.379 (95%CI 1.091 – 1.745)
- 18. Blue light and phototoxicy Blue light exposure↑ Choronic damage Age-related retinal diseases Whether exposure from artificial light could have effects related to retinal diseases is uncertain.
- 19. Conclusion • Exposure of the retina to light levels that exceed the natural defense system may cause damage. • The life-long build-up of oxidative damage, part of which is due to light-induced damage, can contribute to the age-related changes and degenerations observed in the aged retina. • However, there is no evidence that lighting would have any impact on the retina graver than sunlight. • A better understanding of the photo-induced processes in the retina is needed to help to predict what levels of illumination are safe for the normal retina.
- 20. Visible Light and the Retina Yasuo Yanagi Associate Professor: Duke-NUS medical School Singapore National Eye Centre/ Singapore Eye Research Institute
Editor's Notes
- The retina is the light-sensing tissue that lines the inside of your eyes. It is composed of many sub-layers. It is very delicate.
- As you see, The macula is the most important part of the retina. This area is designed for sensing small objects, and therefore, a good macula is vital in having good visual acuity. You cannot have 6/6 vision without a macula. In the crosssectinal scan, you can see the retina is composed of many sub-layers. It is very delicate. The fovea is the most important part of the macula. This region lies at the anatomical center of the macula. The fovea forms an inward dimple in the retina. This dimple is responsible for viewing fine details.
- Exposure to visible light causes some retinal diseases In 1976, Ham analyzed light-induced retinal damage in monkeys and found that the blue portion of visible light exerts retinal damage. This type of retinal damage is acute and is induced by short-term, intense light exposure such as solar retinopathy from gazing directly at the sun for a short time. Retinal damage from surgical devices such as operating microscopes and endoilluminators during vitrectomy has also been reported.
- Now you might think that people wouldn’t look at the sun would you, but you would be wrong – many people look up into the sky during an eclipse of the sun thinking that just because the light is poor the sun won’t do any damage, and this is simply NOT the case! There DEFINITELY IS enough sunlight during even a total eclipse to cause damage – permanent damage – to the eyes, especially if as is often the case eclipse watchers insist on staring at the phenomenon for long periods. Patients with solar retinopathy usually experience sun exposure through solar eclipse viewing without proper precautions, religious ritual participation, or from mental disturbances via drug intoxication or schizophrenia.
- Retinopathy is a general medical term used to describe any inflammation or degradation in the retina, usually caused by diseases such as diabetes and high blood pressure. The term solar retinopathy is reserved to be used when the inflammation is caused by exposure to sunlight. Most patient notice a very small blind spot – known medically as a scotoma – in the central vision that they can see around. The most diagnostic test for solar retinopathy is the spectral domain optical coherence tomography line scan shown here. Patient with solar retinopathy have an outer retinal hole. Here you notice a very small defect that only affects the outer retina. Fortunately any vision loss is usually recoverable, although it can take from a few months to a year before everything is back to normal.
- The formation of a blind spot can be thought of as being produced on the retina in a similar way as a magnifying glass is able to produce a burn mark on a piece of paper if focussed correctly. Light is focussed through the eye lens which concentrates that light at the back of the eye on the macula. The light from the sun contains very harmful rays that the retina just cannot cope with. It isn’t the heat of the sun that does the damage – it’s the light causing chemical reaction. And this reaction is mediated by lipofuscin or age pigment.
- As shown here, we revealed that in the absence of lipofuscin, light exposure does not induce RPE cell death. However, as shown in the lower panels, when RPE cells were loaded with lipofuscin, intense physiological light exposure did induce cell death. These findings clearly demonstrate that lipofuscin mediates physiological light-induced RPE cell damage by acting as a photosensitizer.
- As mentioned, light-induced retinal toxicity was investigated as a function of wavelength by exposing rhesus monkey retinas to laser illumination, and it was found that sensitivity to threshold damage rose exponentially with decreasing wavelength. Interestingly, this corresponds to the absorption spectrum of lipofuscin, suggesting that lipofuscin mediates light-induced retinal damage, at least in part. The results suggest that lipofuscin is activated by blue light, and its oxidized products have been detected in human RPE cells, suggesting that the photochemical reactions occur in vivo.
- There is therefore strong evidence that light-induced oxidative stress is the cause of retinal destruction. Recent studies have also shown that dysregulation of complement factors may induce chronic inflammation in the RPE. Our results and previously reported results suggest that cellular damage induced by oxidative stress contributes to the pathogenesis of AMD.
- In 1976, Ham analyzed light-induced retinal damage in monkeys and found that the blue portion of visible light exerts retinal damage. Although acute light-induced damage has been investigated extensively since the late 20th century, little attention has been paid to chronic light phototoxicity until recently.
- , and animal experiments and in vitro studies suggest that cumulative blue light exposure below the levels causing acute effects also can induce photochemical retinal damage, suggesting that damage induced by chronic phototoxic reactions occurring in the retina may be involved in the etiology of debilitating ocular conditions.
- The vision loss is irreversible.
- “There is no consistent evidence from epidemiological studies regarding the effect of long-term exposure to sunlight, specifically the blue component of sunlight and photochemical damage to the retina, which may contribute to age-related macular degeneration (AMD) later in life.
- The question people often ask is “can blue light cause blindness?” – and the answer of course is no. unless you directly gaze high-brightness light directly. Then, does it increase the risk of retinal diseases? We still do not have solid evidence. there is no evidence that lighting would have any impact on the retina graver than sunlight. Whether exposure from artificial light could have effects related to AMD is uncertain. Chronic exposure to blue light from improperly used lamps could, in theory, induce photochemical retinal damage in certain circumstances. There is however no evidence that this constitutes a risk in practice. It is unlikely that chronic exposures to artificial light during normal lighting conditions could induce damage to the retina
- And during the patience period maybe a thought or two should be given to the old adage “prevention is better than cure”.