QUESTION: My husband is 36. During his high school years and shortly after graduation (for a total of about five years) he was heavily into drugs - acid, downers, speed, basically anything he could lay his hands on. He hasn't taken drugs since then. But he tells me he experiences flashbacks. He says he sees "zzzz's" in his left eye. It lasts for a half hour and he cannot see through that eye clearly. Can this be a flashback? - Very Concerned.

ANSWER: I'm concerned too, but not about flashbacks from his former drug use. Flashbacks are brief reappearances of the hallucinations or distorted perceptions experienced by those who have taken psychedelic drugs like LSD, PCP or mescaline. They occur days or weeks after the last dose and usually disappear in time.Even had your husband indulged in those kinds of hallucinogens, he could not lay his present eyesight disturbance to them. It would be most unusual to suffer flashback after 13 years. My concern is that the zigzag images he reports could indicate retinal problems, disturbance of the lining of the rear of the eye. That should be investigated. Untreated, it could get him into serious sight trouble.

Another possibility is migraine, even if there were no headaches involved in the episodes. Certain migraines are painless. Also, this aberrant sight symptom might reflect disturbed blood circulation to the eye. Make an appointment with an ophthalmologist, an eye specialist.

QUESTION: I am 57 and have been enduring cluster headaches for 14 years. I have tried various medicines for them, with little or no relief. Could you give me a list of medicines you've found helpful, perhaps some I haven't tried? - A.K.

ANSWER: There are drugs to prevent cluster headaches and to abort an individual attack. Those used preventively include methysergide, ergotamine, calcium channel blockers (diltiazem and nifedipine for examples), prednisone, and lithium. Ergotamine is also used to stop an attack. Giving oxygen also helps.

For other readers, cluster headaches are episodes of one-sided pain of unbearable intensity that last less than an hour and are accompanied by eye tearing and nose dripping on the same side. They are called cluster headaches because attacks come in bunches of one to three a day for from six to 12 weeks, then disappear for sometimes years. All these time statistics are averages. The numbers and duration of cluster episodes can vary considerably. I am sending on the headache report, which goes into the subject in greater detail. Others may order by writing Dr. Donohue/No.15, Box 830, Gibbstown, NJ 08027-9909, enclosing a long, stamped, self-addressed envelope and $2.

Dr. Donohue welcomes reader mail but regrets that, due to the tremendous volume received daily, he is unable to answer individual letters. Readers' questions are incorporated in his column whenever possible.