How will the eclipse blind me?
There has been a lot of chatter regarding the solar eclipse and the best way to view it without causing eye damage. In this post, I want to talk a little bit about solar retinopathy which could result from direct viewing of the solar eclipse. This is what happens with prolonged direct viewing of the sun or other similar amounts of light. Everyone's eye is similar to a camera. The lens of the eye focuses light on the film which is called the retina. Have you ever used a magnifying glass to light something on fire with the rays of the sun? The magnifying glass focuses the light to what is called a "focal point." When you use a magnifying glass, the light is focused to create an "image" of the sun at the specific point you are trying to heat up. It is almost like you have a miniature sun at that point, and that is why you are able to cause enough heat to actually light something on fire. Your eye basically does the same thing when looking at the sun; it basically focuses all of the light from the sun on a specific location on the retina called the fovea. As you can imagine, this intense light exposure can cause severe damage to your retina. A little bit like lighting a leaf on fire with a magnifying glass. The extra light results in damage to the photoreceptors which sense light. When this area is significantly damaged, it cannot regenerate which will result in a blind spot in the vision. However, this blind spot is the area where we identify details such as faces, and small letters. The resulting damage can be very similar to the age related macular degeneration that can be found as we grow older. This whole discussion is why it is important to reduce the amount of light that reaches the retina when viewing the solar eclipse with specialized glasses, etc. NASA has some resources regarding the correct type of glasses https://eclipse2017.nasa.gov/safety. So be safe and have fun viewing the eclipse!