By Richard P. Holm MD
The leading cause of blindness worldwide is from cataracts. That is the clouding and browning of the natural lens, which is mostly due to aging and sun-damage. It is like the difference in swimming with goggles in a crystal clear pool versus in an algae-blooming prairie lake in August. People with cataracts progressively lose their vision as their lens opacifies.
More than 2600 years ago, a physician from India was the first to write about cataract surgery. He described using a curved needle to push back completely clouded over lenses into the vitreous fluid in the middle of the eye, out of the field of vision. This reportedly would return some vision for people completely blinded in that eye by a cataract, and he called it “couching.”
The vitreous is the sack of fluid that separates the iris, pupil, and lens at the front of the eye from the retina or light sensitive nerve blanket that catches the image in the back of the eye and sends the photo message to the brain. Pushing or couching cataracts back and hopefully to the side into that vitreous would allow light through to the retina, however the vitreous would be disrupted, could possibly become infected, and there would be no lens to focus the light. Still this was better than nothing.
Couching cataracts eventually spread to China, Arabia, Africa and Europe, but it is not difficult to understand why this procedure was used only as a last resort. Other methods to remove the lens completely from the eye, without disrupting the vitreous, gradually were developed during the Middle Ages and up unto today. But until we learned how to control infection in the mid-1800s this was still very dangerous and not commonly done. Eventually very thick external glasses were devised that would replace the lost natural lens, and starting in the 1940s these removable glasses began to be replaced with lenses that are surgically implanted into the eye.
Now the surgery to extract opaque and diseased cataract lenses is much better, and keeps improving. And the lenses we implant continue to advance as well.
It is like cleaning out all that vision blocking algae, and swimming in a crystal clear pool.