Over the break I did a little research on contact lenses, because I wear them and was curious how an object with the same shape could correct for so many different vision disorders, including myopia, hyperopia, astigmatism, and more. I stumbled upon the all-knowing website howstuffworks.com (http://health.howstuffworks.com/contact-lens2.htm) and read a nice little article on the different types of contact lenses (there are more than just one!) and how they work.
I suffer from myopia, and knew that the number of the contact prescription referred to the strength of refraction of the lenses (my lenses are -3.25 and -3.75), but I never knew what the – sign meant. After reading the article, I learned that the – sign refers to lenses that correct for myopia, and + lenses correct for hyperopia. I also learned that minus lenses, even though though don’t appear to be, are in fact concave. I tried to examine my contacts to see the concavity for myself, but I couldn’t really see it, so I’ll have to assume that since my lenses work, they are in fact concave and thinner in the very center than around the edges, thus refracting the light like a normal concave lens like we see in the book.
I was also astonished to learn that there are contact lenses that replace bifocal glasses! Called translating lenses, they correct for myopia at the bottom and hyperopia at the top, just like bifocal glasses. However, the most amazing type of contact lenses I learned about about called corneal reshaping lenses, which do precisely what their name says. You wear these special “ortho-k” lenses at night, and they gradually reshape the cornea, correcting the focal point of the cornea and enhancing your vision! One doctor said they can correct up to 2-3 diopters in just a couple weeks! This is all, of course, a non-surgical alternative to LASIK, and the results don’t seem to be quite as good as LASIK, but for those who are afraid of putting their eye under a laser, this could be a valid alternative.
