Most of us regard our sense of sight as priceless, and yet billions live with imperfect vision. Fortunately, properly designed eyeglasses can improve many types of defective eyesight, thanks to the scienace of corrective lenses.
Of Cameras and Eyes
As explained in Live Science, “The human eye belongs to a general group of eyes found in nature called ‘camera-type eyes.'”
A camera is basically a lens that focuses images onto a light-sensitive surface. For the human eye, the lens is called the cornea, while in place of the light-sensitive capacitor array in a CCD camera, the human eye has bundles of millions of photoreceptors that are responsive to color and lighting levels.
Defects in the Eye
In the human eye, the distance between cornea (lens) and retina (projection surface) is fixed, but the cornea is flexible enough to adjust itself to focus on objects near and far by thickening and thinning itself as necessary. That is, that’s how it’s supposed to work.
Unfortunately, through birth or from aging, many of us have cornea lenses that can’t adjust enough to cover the whole range of distance viewing. And presently, the world is suffering what scientists are calling a ‘silent epidemic‘ of myopia, in which 42% of Americans are afflicted. Fortunately, eyeglasses can correct vision.
Eyeglasses correct defects in human vision by placing a lens made of glass or plastic in front of the natural lens (cornea). The refractive power of lenses is measured in diopters, which can be plus or minus depending on whether the lens is thickest or thinnest in the center. Diopters of the lenses can be added together to create a compound lens system with the proper focal length for our eyes to bring objects into clarity.
As optician Bob Broten writes, “Myopia (nearsightedness) occurs when a distant object looks blurred because the image comes into focus before it reaches the retina. Myopia can be corrected with a minus lens, which moves the focus farther back.” Likewise, farsightedness is corrected with a plus lens, while astigmatism is corrected with lenses of greater geometric complexity.
What You Can Do
If you have any question about your vision, consider taking an online eye test, and see an optician about ensuring your vision lives up to its full potential.