Notifiblog: How Stuff Works Thursday! (on Friday)

I had a topic already in mind yesterday, but the worky people needed me more than the Notifiblog did. So, today let's look at How Corrective Lenses Work! Thanks to www.howstuffworks.com, we can do just that...

(from HSW.com) "When you look at something, three things must happen:

• The image must be reduced in size to fit onto the retina.
• The scattered light must come together -- that is, it must focus -- at the surface of the retina.
• The image must be curved to match the curve of the retina."

(from HSW.com) "The strength of a lens is determined by the lens material and the angle of the curve that is ground into the lens. Lens strength is expressed as diopters (D), which indicates how much the light is bent. The higher the diopter, the stronger the lens. Also, a plus (+) or minus (-) sign before the diopter strength indicates the type of lens.

"Plus and minus lenses can be combined, with the total lens type being the algebraic sum of the two." There are 12 standard steps to grinding most lens blanks into the correct shape to correct vision. There is so much good information that won't fit here, so I strongly recommend reading the article at least from page 6!

Benjamin Franklin is credited with inventing the bifocal corrective lens, but who came up with the idea of putting a curved piece of glass to the eye to improve vision? Sadly, that name is lost to history. However, the first person to copy this invention and share it with the world is believed to be Giordano's colleague Friar Alessandro della Spina of Pisa (d. 1313). (Sorry, no Wikipedia page exists for him, yet.) He began making eyeglasses in Italy around 1286 CE.

Everyone in my family--even the ones to whom I'm not biologically related-- wears glasses or contact lenses. I'm next. At least I understand what I'm getting when I get glasses. (I'm probably not a contact lenses person, but who knows, eh!)