After finally completing a residency at a respectable big-city hospital, you are offered a job with the Docs-R-Us health maintenance organization. Its not exactly the position of your dreams, but you feel a sense of urgency to start paying off your medical school debts. Although seeing a patient every 5 minutes was never your idea of a utopian medical practice, you agree to the stipulations in the contract and sign on the dotted line.

The bold corporate vision of Docs-R-Us is to do for medicine what fast food has done for the restaurant business. Consistent with that vision is the clause in your contract requiring you to limit your physical examination to inspection of only one organ. You are asked to declare which of all the organs in the body you will examine in all your patients. After pondering this for a moment--which organ will provide the astute examiner the most information about the health of the entire body--you select the eye.

Your first patient is a man in his mid-50s, dressed in business suit, and looking like he's obviously enjoyed a few too many cheeseburgers. He apologizes for being late and mumbles something about how rush-hour traffic always gets his blood boiling.

Doc, I've been having these awful chest pains. Can you fix me?

Almost reflexively, you start to reach for your stethoscope. But remembering your contract, you suppress the urge. Instead, you reach into your desk and pull out an ophthalmoscope.

The ophthalmoscope is an instrument that consist of a mirror that reflects light into the eye, a viewing aperture, and a series of lenses that magnify the interior of the eyeball. Adjustment of the lens refraction allows the examiner to visualize different parts of the eye. Focusing closely allows inspection of anterior structures, such as the conjunctiva, cornea, iris, and anterior chamber. Focusing deeper and peering through the pupil, the posterior cavity, retina, and fundus can be illuminated.

As you scan the patient's chart, you notice that no blood pressure measurement has been recorded. More cutbacks, obviously. No matter, you think to yourself as you shine the light into the man's eye. You recall from medical school that hypertension (high blood pressure) leaves clues on the retina that a skilled observer should be able to pick up. Sure enough, the retinal arterioles are significantly narrowed. Some of them even resemble copper wire, with thickened walls and a reddish-brown discoloration. These findings are characteristic of long-standing hypertension.

As you explore the retina further, you notice several tiny red spots and recognize them as aneurysms associated with diabetes mellitus. These small-vessel malformations occur in 60 % of patients who have had diabetes for 10 years or more. Diabetic patients also develop other retinal changes, as well as cataracts and retinal detachments--but these are notably absent in this patient.

Just before you complete the retinal exam, you make one final discover. You see a couple of yellow spots known as Hollenhorst plaques. These are caused by particles of cholesterol, usually originating in the carotid artery, that have broken free and come to rest in the retinal arterioles. They are frequently a sign of impending serious cardiovascular disease.

So whaddya think, Doc? Probably just gas?

Of the known risk factors for heart attack, this man has at least three--diabetes, hypertension, and atherosclerosis. Thank goodness he doesn't smoke. All this you determined with vital sign measurements, a cardiac exam, or laboratory studies. The administrators would be so proud of you.

For a moment you reflect on what an excellent choice you made in selecting the eye as the subject of your exam. Through careful inspection of the eye, a huge array of systemic disorders can be diagnosed. A yellowish (jaundice) sclera is an indication of liver and/or gallbladder problems. An abnormally dilated pupil is an indication of shock or of various nervous system disorders. Increased pressure in the brain from infection, stroke, or trauma leads to blurring of the optic disc. Sickle cell anemia produces convoluted retinal vessels. High copper levels in the body (Wilson's disease) is often diagnosed by a brown band around the iris. Small-vessel bleeding in the retina reflects certain protein-producing malignancies. Clouding of the cornea can be the first clue to some inherited disorders of sugar metabolism. As the English physician Peter Latham advised his medical students more than a century ago, In the eye you will see all diseased in miniature, and you will see them as through a glass.

I'm sorry, sir, you tell your patient, I'm going to have to admit you to the hospital for a workup for possible heart disease. Please get your things together and follow the nurse.

It's a little sudden, but I guess so. Thanks Doc. He pauses as he heads for the door. Say, Doc, before I head up to hospital room you think I could step out for a smoke?

A moment after he leaves, the receptionist steps in to inform you that your next two patients have canceled. Good, you say, that will give me at least 10 minute to scan the paper for another job.