She had a headache for months. Then she could barely see.

The 61-year-old woman put on her reading glasses to try to decipher the tiny black circles on the back of the instant pudding packet. Was it two cups of milk? Or three? The glasses didn't seem to help. The blurry, faded markings refused to become letters. The right side of her head was throbbing – as it had for weeks. The constant worsening of the headache made things more difficult, and reading this label certainly didn't help her. She rubbed her forehead, then lowered her hand to cover her right eye. The box disappeared into the darkness. She could only see the upper left corner of the instructions. Everything else was black. She quickly moved her hand to cover her left eye. The tiny letters became sharp.

She went back to the right: blackness. Left: light and letters. That scared her. In the past few months she has had one of the worst headaches she has ever had with a headache in her life. One that wouldn't go away no matter how much ibuprofen she took. One that got through all the different medications she was taking for her migraines. Was that terrible headache affecting your vision now? The neurologists she saw over the years always asked her about visual changes. She had never had them before.

"Do you want me to take you to the hospital?" her husband asked worriedly when she told him about her almost blind left eye. "That could be serious." She thought for a moment. No, tomorrow was Monday; Her neurologist's office would be open and the doctor would see her immediately. That way she was always reliable.

The patient had severe headaches for most of her adult life. They were always on the right. They always knocked. They can last days, weeks, or sometimes months. Loud noises were always annoying. With a really bad headache, her eye would water and her nose would run, right on that side. Bending down was torture. Her headache had been so severe in the past few weeks that she had to leave something there if she dropped it on the floor. When she bent down, the stomping was unbearable.

When she was younger, the headache seemed to come along with her periods. In her mid-thirties, after having her daughter, her uterus and ovaries were removed. She was hopeful for the first few weeks, but then the episodes of throbbing pain came back, as bad as ever. Her doctors told her it was a migraine. And it seemed like she had taken every migraine drug that had ever been made. Her newest doctor had them take a seizure medication that was used to prevent migraines, along with Excedrin migraines, which she was supposed to take once they started. She had been on this twin therapy for weeks, but the headache just didn't go away.

A "second heart"

The woman saw her neurologist early the next afternoon. The doctor was worried too. She ordered an M.R.I. and referred the patient to Dr. Robert Lesser, a neuro-ophthalmologist outside of New Haven, Conn. In Lesser's examination room, the patient explained, first to the technician, then to the doctor, that she had had this headache for months. Sometimes the pain was worse, sometimes better, but it was always there, pounding and pounding on the right side of her head. It was as if she had a second heart in her skull that was beating, squeezing, and crowding. Recently her vision seemed to be getting worse and more blurry. Blinking didn't help. And then she discovered that she could barely see anything when she covered her right eye.

The constant presence of headaches and for weeks immediately reminded Lesser of a rare condition called Hemicrania Continua. As the name suggests, it is a one-sided headache that lasts well beyond its normal duration and is often accompanied by eye redness or tears. It's a strange type of headache that is related to other strange headaches – like cluster headaches – where the underlying causes are still puzzling. He had seen maybe 20 cases in the past. While these patients had frequent eye symptoms, they were always on the same side as the headache. This patient reported changes in the other eye. What would cause pain on the one hand and loss of vision on the other? Multiple sclerosis can cause neurological symptoms anywhere in the body. Or was that a mass somewhere in her brain? It would take multiple expansive lesions to cause the pressure and pain she described and affect her vision. But she already had an M.R.I. had and nothing was seen.

Lesser examined her eyes. They looked normal even up close. Every student responded equally to light. He took photos of the fundus of her eyes, first on the right, then on the left. There are two places of particular interest in the retina. The papilla is the area where the nerves that carry visual information connect to the brain. Increased pressure in the eye due to a mass or glaucoma can cause swelling or atrophy of the nerves, which can be common. But in this woman, the optic nerve looked perfectly normal on both sides. Most of the visual receptors are located in another region of the retina called the macula. This tiny region is responsible for most of our perception of color and detail. In this patient, the macula was normal on the right, but swollen and discolored on the left.

Separate

When Lesser saw this, he knew that the headache and the visual changes were caused by separate disease processes. The headache was most likely Hemicrania Continua. The test to confirm this diagnosis is a therapeutic study of an ancient medicine called indomethacin, a relative of ibuprofen and naproxen. This type of headache responds wonderfully to this particular drug, probably because it more easily crosses the blood-brain barrier that keeps so many other drugs away.

The lesion on the woman's retina was more worrying. It could be something common, like central serous chorioretinopathy (C.S.C.), which causes spots in the retina to swell. It's more common in young people and people with Type A personalities. C.S.C. can cause vision problems and sometimes requires treatment if it doesn't improve on its own within a month or two. That was the most likely diagnosis. But there was another possibility that was far more serious: malignant melanoma of the retina. This is much less common, but it can be fatal. The patient had to be examined by a retinal specialist to distinguish between these two very different possibilities. Lesser sat down with the woman. It was good news – bad kind of entertainment. She may be able to get rid of her lifelong headache with a pill that she takes twice a day. But she can also have one of the most dangerous types of cancer known.

Dark side, light side

The woman saw Dr. Thomas Berenberg, a retinal specialist in Lesser's group practice. It was melanoma. She had radiation therapy that eliminated the growth in her eye. Even though that was almost a year and a half ago, she still needs regular checkups to make sure it stays away.

On the lighter side, she started taking indomethacin right after seeing Lesser. It took a few weeks, but eventually her headache went away and mostly stayed away. She had an indication of recurrence and immediately started the indomethacin and the throbbing pain went away and has not come back. Even so, her eyesight in her left eye did not recover, forcing her to retire from her job as a court reporter. The double vision caused by the damaged eye prevents them from reading. However, she is optimistic. She has the feeling of avoiding a bullet. The cursed throbbing pain led to a diagnosis that saved her life. And as an added bonus, she got rid of her constant headaches. Last year she and her husband moved to South Carolina, where their daughter lives. And the woman gets a contact lens to block the view in her left eye so that she can read again very soon. All in all, she tells me, she feels pretty happy.