The Unexpected Warning

The man in his early thirties had begun seeing black dots in his left eye. He had no pain and no other symptoms in the rest of his body. He had been prescribed steroids, but the black dots had not gone away. In fact, there were many more now, and his vision was increasingly blurry. When he came to see Dr. James Dunn of the Retina Service at Wills Eye, the man’s vision had degraded to 20/400.

Dr. Dunn reviewed the man’s medical history. He found no obvious systemic disease or condition. He noted that the problem was in one eye and not the other. He also noted that the disease was progressing slowly, not a fast, hard hit. The physician who referred the patient suspected toxoplasmosis, which is caused by protozoa, small single-cell organisms. Yes, it might be, Dr. Dunn thought.

Dr. Dunn then examined the man’s eye. There was no significant inflammation in the front portion. However, in the back, there was a ball-like shape over his optic nerve with a small spot of bleeding next to it. Dr. Dunn noted the white color and the fact that it had a three-dimensional appearance to it.

Pattern recognition is essential in making a diagnosis. By coupling a patient’s medical history with observations in the eye, the clinician is trained to recognize patterns of disease. In that way, the clinician rules out each of the wrong causes until the correct one is the only that remains.

In this man, Dr. Dunn recognized the pattern of fungal endophthalmitis, a very treatable condition. But the real crux of the question was where did the fungus come from? Like many diseases in faraway parts of the body that show symptoms in the eye, Dr. Dunn had to determine if there was another infection somewhere, such as a heart infection that might threaten the patient’s long-term health or life.

Dr. Dunn had a hard question to ask. One that required a sense of trust in the physician. He asked the man whether he used injectable drugs. The man did not hesitate or avoid the question. “Yes,” he said.

The arteries leading to the eye are some of the first blood vessel branches after blood leaves the heart. That is why pathogens traveling in the blood, such as fungi, can land in the eye. Having no idea that such an infection was even possible, the man was shocked and shaken. Dr. Dunn and his pattern recognition had just turned a mysterious eye disease into the man’s conviction to end his use of injectable drugs.