Wednesday, March 16, 2011

Eagle Vision

When people talk about eagle vision, it is a perfect metaphor for the ultimate visual system.  Eagles, hawks, and birds of prey have the best sight of any animal.  Just the need to fly requires excellent vision, but when you have to spot your dinner on the ground and dive after it at incredible speeds, you will go hungry if you don’t see exceptionally well.

First of all, their eyes are enormous.  Our eyes take up 2 percent of our face, but these birds can have eyes that are 15-20% of their head.  Sometimes, their eyes weigh more than their brain!  They also have an extra eyelid that is transparent.  They can blink and still keep seeing.  Inside their retinas, there are other differences from us.  We have two special receptor cells in our retinas to convert light to electrical signals—the rods and cones.  Birds have an extra receptor cell that probably allows them to see colors that we could not even describe.

It doesn’t stop there.  As Sy Montgomery notes in her 2010 book, Birdology, the bird’s retinas are densely packed with these receptor cells.  In our eyes, a special area of the retina called the fovea contains our best sharpest vision.  We tend to have 200,000 cones/mm2 but eagles could have over a 1,000,000 cones/mm2.  This would create a world of such detail that we would need microscopes to approximate what they see.  Remember when you saw your first HD television next to a regular picture.  Imagine a few levels of detail beyond that and you can start to think how these birds see the world.

Wednesday, March 2, 2011

Dry Eyes

Dry eyes can drive patients and doctors crazy.  We all want the same thing--to see everything perfectly clearly 24/7 and to not be bothered by our eyes.  But when problems happen with our tears, then this perfectly balanced system causes all kinds of problems.  Even with problems of blurred vision 5% of the time, that would be enough to bother someone on a daily basis.

Our eyes need to be moist to be happy.  Just think of the last time your nose was stuffy and you slept with your mouth open.  My morning, the throat becomes raw and sore.  On top of that, the eyes have more nerves for pain reception and sensation than almost any other part of the body.  Tears are important because of their special properties.  They are made of water, mucus, and fats that in the right mixture, coat and protect and provide a brilliantly perfectly smooth surface that helps to bend light and start the magical process of sight.

As we get older, this system can start to break down and because it is so complex, there are a lot of ways to treat it.  Unfortunately for some, all of our current methods are not enough and for these unlucky people, they have to fight on a daily basis for comfort and vision.

We have been very happy with our initial results for the Intense Pulsed Light Treatment for dry eyes.  So far, our patients are more comfortable with better vision and using fewer drops.  I'm excited with what we can do!