Eye Didn't Know!

Why do you dilate my pupils?

Did you know? Patients frequently ask why it's necessary to dilate the pupils during a complete eye examination. It's simple, really. Imagine the difference between looking into a room through a keyhole, and looking in through a large window. If you really want to get a good view inside the room, the large window gives a much more complete view.

Similarly, dilating the pupil enables the ophthalmologist to view the entire back of the eye. What are we looking for? There are hundreds of things that can go wrong inside the eye, (many of which have no symptoms). We're checking to see if everything is normal. We look at the optic nerve, the blood vessels, and the retina, including the central retina, called the macula. If you have a specific complaint, like floaters, or a family history of glaucoma, or blurred central vision, obviously we will pay particular attention to the part of the eye which is most likely involved.

Here is a diagram which shows the advantage of a dilated pupil. The diagram is incorrect, though. With a dilated pupil, and the proper equipment and technique, the entire back of the eye can be examined (including the periphery), not just the part shown in the diagram.

 

(courtesy of the National Eye Institute) 

Did you also know? In 1823, a Dr. Purkinje was the first to ever look inside a living human eye, when he devised the optics to do so. It was not until 1850 that another ophthalmologist, Hermann von Helmholtz, invented the ophthalmoscope independently and publicized his device that other doctors finally were able to look inside the eye and more accurately diagnose its conditions. Read more about the history of the ophthalmoscope here.

Measuring Eye Pressure

Did you know? Until 1905 there was no objective way to measure pressure within the eye. In that year, Norwegian ophthalmologist Hjalmar Schiotz invented the first tonometer, which now bears his name, the Schiotz tonometer.

Until this time, doctors estimated pressure within the eye by pushing on the eye through the eyelid, and guessing, much like you might push on a bicycle tire with your thumb and guess the pressure. The Schiotz tonometer actually works in much the same way, it measures the weight necessary to indent the cornea a standard amount.

Knowing the pressure more accurately allows us to better diagnose and treat glaucoma, a disease usually caused by elevated eye pressure damaging the optic nerve.

The Schiotz tonometer is still used in many parts of the world, and when I trained, it was what most doctors used as a portable tonometer.

Did you also know? Dr. Schiotz was also responsible for introducing the concept of sterilizing surgical instruments (by boiling) to Norway.

Happy Birthday Abe!

Did you know? There is a story about Abraham Lincoln seeing his ghost while looking into a mirror from his bed, shortly after being elected in 1860. By studying numerous photographs and portraits of Lincoln, ophthalmologists have determined that Lincoln had a weakness of a muscle in his left eye (the trochlea), which made the eye unable to look downward in certain positions, including when trying to look into a mirror from a supine position. This would explain his double vision during the incident. Others have ascribed this story to a mirror having two reflecting surfaces, but I find that less convincing.

Did you also know? Physicians say there’s a 50/50 chance that Lincoln had Marfan’s Syndrome, which causes elongation of the hands and jaw during adulthood, due to an excess of human growth hormone. (Marfan's Syndrome can also can dislocation of the lens within the eye).

photo courtesy wikimedia commons

Happy Birthday Darwin!

Did you know? Yesterday I also missed the birthday of Charles Darwin! Happy Birthday!

Did you also know? I'll write about Charles Darwin and ophthalmology in a later post!

A Way With Eyewords?

Did you know? I had the pleasure this week of hearing Martha Barnette speak. Martha Barnette is a language expert, author, and co-host of A Way With Words, the wonderful syndicated radio show from KPBS, San Diego. This week I will write about a few of my favorite ophthalmology words. Let's start with ophthalmology! The origin is not that interesting, ophthos=eye logos=words, so ophthalmology = study of eyes. What's unusual, though, is that ophthalmology is one of those words which is simply IMPOSSIBLE to spell if you are not an ophthalmologist. (Close your eyes and spell it! I dare you.)

Did you also know? There are only a handful of other words in English with the letters phth together. Diphtheria (a severe disease of the throat, rare now due to vaccinations), diphthong (a syllable formed by two vowel sounds, like in boil or foul), naphtha and its derivatives (a volatile hydrocarbon), and my favorite, phthisis (what occurs when a diseased eye shrivels up!)

Ben Franklin and Bifocals

Did you know? Benjamin Franklin (1706-1790) really did invent bifocals! Franklin was a prolific inventor. He grew tired of switching from distance glasses to reading glasses, and suggested to his optician that each lens be cut in half and the distance lens be placed atop the near lens. Thus, bifocals were born! A detailed summary of Franklin's invention exists here.

image: wikipedia public domain photos

Did you also know? My favorite Franklin invention is the glass harmonica. It consisted of crystal glasses arranged in a manner that they can be rotated and "played" by a wet finger. Mozart even wrote a concerto for glass harmonica! Here's a picture of Franklin playing the glass harmonica, wearing his bifocals.