Meeting Called by: Pre-Optometry Club
Duration: 1 hour
Guest Speaker: Dr Yuhas, The Retina: An Overview
- Dr Yuhas is a professor at the OSU Optometry school, teaching courses in glaucoma and ocular disease. He does research and clinical work with the retina, blue light exposure and traumatic brain injury.
- If the eye was a camera, the retina would be the film within the camera, light being focused on it via the lens and cornea. The retina transduces light into signals sent into the brain.
- The retina is the only place in the body where we can observe the nerves and blood vessels as they are, which is a powerful diagnostic tool. In the cross section, the macula shows a dip in the tissue and all the layers of tissue, 10 layers total within the retina. In the bottom layer are the rods and cones which collect the light information.
- Time spent on screens is increasing for all age groups, will it damage our eyes? Blue light is the wavelength of light that is emitted from computers, phones and most/all technology. The danger with blue light has to do with the amount of energy the short wavelength light emits. Blue light lies within 400 nm wavelengths, so among the shortest wavelengths we can register.
- Sunlight is mostly blue light, similar to electronics. When its absorbed by the retina, free radicals are created within the back of the eye, which can damage cell membranes, proteins and DNA. Studies have shown RPE cells % of survival decrease with longer exposure time to blue light.
- Blue light can also cause damage to photoreceptors, causing an overall loss of them within the retina. The rods will shrink down in response to blue light and will become encased within inflammatory material and be destroyed. A study done on genetically modified cells shows that as blue light exposure increased, an increase of calcium intake also occurred into the cell. Too much calcium can cause apoptosis of the cells, showing “that retinal cells can die of an over saturation of calcium in response to blue light.”
- Most studies show no risk of blue light exposure and retinal disease , even though some suggest eye damage and worsening of existing diseases. In summary, lab studies show its danger, but evidence in humans contradicts this correlation.
- Melanin is a protective element pigment that absorbs high energy light in the retina, and as an antioxidant. It “eats” the free radicals and prevents the damage they can cause. Studies show higher levels of melanin can withstand higher blue light exposure in comparison to those with less. MAC pigments also act as antioxidants within the retina.
- How can electronics be worse than the sun? Screens we view daily can be as high as 50 lux (units of brightness). A cloudy day is also about 1000 lux, but a sunny day is roughly 100,000 lux. Even under long term viewing conditions, none of the current technology screens can cause serious concern to damage the retina. This also means blue light blocking products don’t do much to protect us or make us more comfortable when using our technology. This does not mean the light cannot affect sleep, only that it is not significantly more dangerous than the sun itself.
- TBI: an acquired brain injury that occurs when a sudden trauma causes damage to the brain. Globally about 10 million cases a year, in America, about 2.5 million but TBI is severely underreported. 70-90% of cases are mild, meaning brief or no loss of consciousness and no more than a day loss of memory.
- TBIs are often repetitive, 35% of sports related TBIs follow a previous injury.
- Diffuse axonal injury: coup countercoup injury, when we initially bang our head nut its movement within the skull damages another area. Causes DAI, axonal deformation and swelling. Damage to the axons causes malfunctions. Enough of these injuries can cause an inflammatory response and an increase of white matter surrounding damaged neurons and tau protein phosphorylation, which disables it to no longer support microtubules within neurons. Changes to neurons within the brain alter cognitive function.
- This pathology is not able to be detected with MRI or any other imaging systems, it can only be observed postmortem.
- There is possible potential for the retina to tell us about these conditions in patients before they die. The retina is like a “brain slice”, showing us neural tissue, and it is susceptible to this pathology change. As the axons that travel from the eye to the brain, they are able to be damaged in a TBI accident. There can also be transsynaptic degeneration, the spreading of neurodegenerative disease to healthy tissues. This begs the option that the disease can spread to the eye even if the eye is not initially affected.
- TBI can decrease the amount of retinal ganglion cells due to a blast injury, studies show. It also occurs for repeated TBI injuries. This could allow clinicians to observe evidence of brain damage by using the accessibility of the retina. Some human based studies have come out in support toTBI causing an increased thinning in the retina, but not all studies show significance in this finding.
- Dr Yuhas’s research is incorporating microtubule structural damage within the retina and repeated TBIs.