Diabetic Retinopathy

Today, diabetic retinopathy remains the leading cause of legal blindness amongst working-age Americans. An estimated 29 million Americans age 20 years or older have either diagnosed diabetes, undiagnosed diabetes, or impaired fasting blood glucose levels. One third of individuals are unaware they even have the disease. The hormone in our body that controls the metabolism of sugar is insulin. In diabetics, insulin is either produced in insufficient quantity or does not function properly upon its target tissues. As a result, abnormal sugar by-products accumulate throughout our body with damaging effects. The longer one has diabetes the more likely they are to develop its complications, and, as previously mentioned, one of the more commonly affected tissues is the retina. Diabetic retinopathy can be one of the most debilitating aspects of long standing diabetic disease. In patients lacking resources, or those who have not been able to control their disease or receive timely treatment, blindness from diabetes still occurs.

As mentioned, the complications of diabetes result from the effects of abnormal blood sugar metabolism on our body, particularly wherever it has small blood vessels. As the duration and extent of diabetic disease grows, especially in light of poor control, these blood vessels become incompetent. Retinal vessels in particular can become abnormally dilated with the tendency to leak fluid, and this results in swelling of the retina, known as macular edema, with the resultant loss of vision. Alternatively, the retinal vessels can close off completely causing ischemia - a lack of oxygen and nutrient perfusion. Ischemia leads to the development of abnormal new blood vessels which have a tendency to bleed and form scar tissue, and these in turn can cause retinal detachments and even total blindness.

First, take a look at this normal retina, you'll see the normal blood vessels with their branches, the orange appearing retinal tissue, and the optic nerve, the yellow circle which carries the visual signal from the retina to the brain.

Figure Coutesy of the National Eye Institute, National Institutes of Health

Now have have a look at this video. What you see here is actually a fluorescein angiogram of a patient with diabetic retinopathy. An angiogram is a sequence of pictures, in this case a movie, of the retina taken after a fluorescent dye is injected in to the patient's blood stream. If you look closely, you'll see the normal large blood vessels of the retina fill as the dye passes int to the retina's circulation but, more importantly, you'll begin to see it leak out of microaneurysms (the tiny little dots) and abnormal neovascular blood vessels. Leakage from microaneursysms causes macular edema and leakage from neovascular blood vessels causes vitreous hemorrhage, or bleeding (in this case, demonstrated by dark shadows obscuring the retina). This patient has both.

Couching

Couching is a method of cataract surgery, and one of the oldest types of surgery of any type, founded and performed over 2000 years ago by the Indian surgeon Sushruta. It's a technique whereby a needle, often times less than sterile, is inserted in to the eye to displace an aged, cataractous lens. Where practiced, it wasn't very elegant but it often sufficed to clear the patient's view to the outside world - that is, if the eye survived the operation. Couching has a fascinating history and those who have been blinded under its knife include the likes of Johann Sebastian Bach (who might have died as a result of it) and George Friederich Handel, and Rembrandt even made artistic studies of it in his Tobias series.

Couching is still practiced in many parts of the world today and not too long ago one of my surgery professors showed me this video of a contemporary couching procedure . You'll need a strong stomach to view it, but I am sure you'll have a better appreciation of modern sterile surgical technique after you're done.

If you want to learn more about couching, I suggest you read the chapter on cataract surgery in the conveniently recommended book, Eyes on Ice & No Blind Mice.

Food Porn & Diabetes

The Nutrition Action Healthletter, a regular publication of The Center for Science in the Public Interest (CSPI), is the largest-circulation health newsletter in North America. Every month, on its back page is a very entertaining and enlightening section titled "Food Porn" - and with a provocative picture to boot! Well, it just so happens that on more than one occasion the not so very coveted Food Porn of the Month Award has gone to Starbucks. One monthly winner, the Coconut Crème and Vanilla Crème Frappuccinos, were found to pack 870 calories and an entire day’s worth of saturated fat into a 20-ounce venti drink, and depending on how you configure your Starbucks drink, 40 to 60g of sugar. I point out Starbucks here since all our children school kids seem to be finding the local barrista a popular hangout but there are a number of such award winners.

Now, with an average daily calorie intake of 1900 or so recommended for women and 2500 or so for men and with a recommended daily sugar intake of 40 grams, one can see where with a frappuccino here, a donut there, and something somewhere else, one might be headed for trouble. I see a great deal of diabetic retinopathy in my practice. Diabetes is becoming quite the epidemic in this country. Of course, many of us can conveniently blame a genetic predisposition, but a lot of it has to do with our tendency to eat a lot and exercise very little. Certainly, the sugar-loaded frappuccinos, sodas and processed drinks we consume in lieu of water don't help either. In the premodern era, we were forced to walk everywhere and there were many times we as humans weren't getting more than a meal a day, much less Starbucks, so we weren't as apt to develop diabetes.

Broadly classified, there are two types of diabetes. Type I is what some folks get at a young age because they can't produce insulin, the hormone that control our body wide sugar metabolism. Type II is what some of us get later in life, due to a dysfunction of whatever insulin we have. Take your typical American living somewhere where he doesn't have - or want - easy access to a gym, takes a car everywhere, spends all day sitting in the office, and then comes home and glues him self to his TV or Tivo, all the while eating high calorie foods. There you have it, the perfect setup for developing Type II diabetes. Basically, the lack of muscle and excess fat mass effectively decrease his insulin sensitivity and ability to metabolize sugars and his chronic overeating of the wrong foods burns out his pancreas, the organ that produces insulin. Early on, those of us who seem to be at risk of or have developed the early signs of diabetes can avoid progression of the disease and the need for medications by changing lifestyle habits, exercising and developing muscle mass, but I rarely see this happen. I read somewhere that most doctors figure patients won't follow exercise and lifestyle/diet advice and hence they go straight to diabetes medications. I also read a study somewhere that they were right. Personal experience as a physician who advocates lifestyle choices confirms this observation - patients generally don't want to make such changes.

Now, as children are drinking sodas at school we're seeing diabetes develop earlier. In either case, Type I or Type II, controlling our blood sugars (and for those of us who are older, our blood pressure and lipid levels) are important in slowing the progression of diabetes. Diabetes generally attacks and damages the small blood vessels in our body, hence patients with diabetes tend to develop problems with their nerves, kidneys, heart, brain, reproductive systems, and retinas - everywhere where small blood vessels are important.

If you have diabetes in your family, or you're overweight, or you may have just developed diabetes, you should be watching what you eat and exercising. That way, you can save yourself a lot of grief. The CSPI, www.cspinet.org, has been an advocate for nutrition and health, food safety, alcohol policy, and sound science. Check out the newsletter and this month's food porn at www.cspinet.org/nah/index.htm. My advice readers, exercise daily and watch what you eat, especially if you have diabetes.

Anatomy

Why has not man a microscopic eye?
For this plain reason,—man is not a fly.
- Alexander Pope, Essay on Man

Today I plan on introducing you to the basic anatomy of the eye. Since I'll be blogging about the eye and its structures here - and since many of us are less than comfortable with the anatomy of the eye - I thought this would be a good exercise early on.

Let’s begin this blog by thinking of the eye as a camera. Like a film camera, light enters the eye from the outside world where it is focused, captured and seen. Simple? Perhaps, but this is, in fact, a very good model for how the eye works and sees. Now, in truth, the eye is a remarkably complex biological entity that takes part in many essential functions besides just sight alone, but this simple analogy serves as a starting point for appreciating the eye, its diseases and therapy, and the biological process of vision.

Figure Courtesy of the National Eye Intitute

At the very front of the eye are its focusing “lenses.” As a matter of fact, the eye has two of them - the cornea externally and the crystalline lens internally. These “lenses” draw in and focus light and images from the world around us. Although the cornea remains fixed, the crystalline lens changes shape and thus focal length readily, like the auto focus feature of a modern camera, and this enables us to see objects at varying distances from the eye clearly. The cornea and crystalline lens are separated by the iris, the ring-shaped tissue that gives us our characteristic eye color. The iris constricts and dilates, like the variable aperture of a camera, and this regulates the amount of light entering our eye. Ultimately, light is captured at the back of our eye on the retina, our “biological film,” and sent by agency of the optic nerve to the brain where it is processed and the visual image seen. Whereas in a camera the internal spaces are empty, those in our eye are not. Instead, they are filled with clear bodily fluids, the aqueous humor between the cornea and lens and the vitreous humor between the lens and retina (and by the way, its the natural aging of the vitreous humor which gives us those bothersome floaters). And as all of these tissues are part of a living, breathing, human being, they are nourished by blood vessels and directed by nerves.

These anatomical structures constitute the integral elements of our biological cameras. Unlike conventional cameras, which nowadays come with lengthy warranties, our biological ones come with no such measure of protection . Even the smallest flaw can impact our ability to see, so we must learn to care for what we have been given and to work with what we have

Introduction

Good Day Readers! This blog will be unlike any other that you have come across. As a retinal surgeon, I have had the good fortune of treating a number of magnificent patients and disease conditions and I plan to share some of that experience, and my expertise, with you here. Of course, I'll be waxing on a number of other topics from medicine and science to literature, art, and history since I am a firm believer that there is a lot more to medicine than just medicine alone. I have had a lot of fun writing and publishing my first book, Eyes on Ice & No Blind Mice, and I believe you'll have just as much fun reading my entries here. Check back frequently for some amazing pictures and videos that I have collected and from active clinical cases. I hope the website will be entertaining and educational and, of course, HIPAA compliant.