An eclipse is a rare astrological event in which the moon passes exactly between the Earth and the Sun, blocking out the Sun’s light. It’s a well known fact that you should never look directly at the Sun, but during the Great American Eclipse, millions of people will be tempted to do precisely that! Let’s take a look at what might happen to your eyes if your curiosity gets the better of you.
The Sun is our ultimate source of all energy. Like all stars it is a giant nuclear reactor, throwing different types of radiation out into the solar system around it. A large amount of the energy it generates is electromagnetic radiation, and this includes infrared (which has a warming effect), visible light, and ultraviolet light, which can damage DNA and is therefore harmful in large doses to living tissue.
Light from the sun can be particularly harmful to the retina if we look directly at the Sun and this is due to the light focusing properties of the cornea and lens. Focusing light brings a large beam of the Sun’s energy to focus at a single point on the central retina, and this greatly magnifies the thermal effect of infrared, resulting in a burn. Heat damaged retinal cells then release a flood of chemicals which cause further damage to surrounding cells. This damage to the retina can lead to permanent loss of central vision, and the appearance of a black smudge in front of everything you look at.
Further damage although temporary, is caused to the cells of the cornea, which will blister and distort when overexposed to UV light. The eyes will tear excessively, become inflamed and feel gritty.
The danger of gazing at an eclipse is potentially greater than trying to looking at the full sun. The darkness that accompanies an eclipse can give you a false sense of security that it’s not that bright, and the natural tendency to squint or avert the eyes is diminished. This increases the amount of light reaching the retina, therefore increasing the chances of retina damage.
So, staring at the sun without proper eye protection is to be avoided. Always limit exposure to the sun and when watching an eclipse use solar-viewing glasses or solar filters.
