ThedaCare Health Matters
On Monday, Aug. 21, there will be a solar eclipse. I imagine you have heard the warnings to not look at the eclipse because it can hurt your eyes. This is not just an “old wife’s tale,” it is good advice.
Why shouldn’t people look directly at the solar eclipse? The reason is that the eye can be damaged due to the intense exposure to damaging light waves from the sun that can damage the retina. The retina is the part of the eye that is full of nerve endings that sense light and send signals to the brain that allow us to perceive images.
Actually, it is never a good idea to look directly at the sun. Under normal circumstances it is uncomfortable so we normally do not look directly at the sun. The iris controls the amount of light that reaches the retina by constricting during bright light and opening when it is darker. The black hole in the center of the iris is called the pupil. Also, we naturally squint to limit damaging sun exposure.
During a solar eclipse, the moon passes between the sun and the earth blocking the light. The moon casts a huge shadow over the earth. It is possible to look at the sun since the light does not seem as intense. The shadow causes the pupil to dilate and this can allow damaging sun rays to get to the retina.
In Wisconsin, the eclipse will not be full. In other words, the sun will not be blocked out 100 percent. Even though the sun will not be so bright, there will still be damaging sun rays present. In areas where the eclipse is 100 percent the eclipse can be safely visualized for the moment of total sun blockage. However, as the moon passes by the sun, the intense sun rays suddenly appear and can cause damage before the iris can react and restrict.