Inquiring Readers Write

By Fred Bove, M.D., Ph.D.

This series of questions and answers is a summary of several letters received from readers.

Question: I have recently been diagnosed with glaucoma. I use several medications, including a small patch that is inserted under the eyelid. Is there any problem with diving?

Answer: Glaucoma causes increased pressure inside the eye and can damage the retina, resulting in reduced vision and, ultimately, blindness. The pressure in the eye is related to ambient pressure, so when you are underwater, the pressure in the eye is not increased in relative terms. If you can tolerate moderate exercise you should not have problems diving. The medications should not be affected by diving, although if your mask floods, the medication patch may be damaged by the water. (Glaucoma is a serious disease. Pain in the eye or blurred vision should not be ignored. A simple test can be done to measure eye pressure and detect this disease early.)

Question: I recently underwent a procedure called laser keratectomy to improve my vision. Is it safe to dive?

Answer: Two recent surgical procedures have been used to change the refraction of the cornea, the clear area in the front of the eye. These procedures improve vision and often allow the individual to see without eyeglasses. Radial keratotomy involved eight incisions in the cornea that changed its curvature and improved vision. This procedure weakens the cornea and cases of corneal rupture were reported. A more recent procedure called laser keratectomy is thought to minimize weakening of the cornea. This produces a change in the curvature of the cornea by shaving very fine layers from it using a laser. No deep cuts are produced. The cornea can be reshaped using computer control and is not weakened. The data on diving after this procedure are not currently available but some observations indicate there should not be a problem. You should wait three months or more to allow complete healing. There is still some concern for diving with radial keratotomy because of the weakened cornea. There are people who have had both procedures diving.

Question: I have recently recovered from a stroke. Studies of the arteries in the neck show no blockages, a magnetic resonance image (MRI) showed no permanent damage. I am presently being treated with the blood thinner warfarin. Is it possible to return to diving and is there any concern with recurrence of the stroke or problems with the blood thinner?

Answer: The cause of your stroke is presently unknown. In the absence of obvious risk factors and no abnormalities of the blood vessels, we would look for a source of a blood clot in the heart. This could occur because of abnormal heart rhythm or because of abnormality of the heart structure. These possibilities should be examined to rule out other possible causes. If you have no neurologic abnormalities, you should have no problem with diving. You should be cautious about injury and bruises because of the warfarin. Since there is no identified cause of the stroke, you should be sure you can exercise safely and not develop any transient neurologic abnormalities.

Question: A patient with a ventricular septal defect (VSD) in the heart wishes to dive. Is there any risk of air bubbles crossing from the venous circulation to the arteries and causing an air embolism?

Answer: In our textbook of diving medicine (Bove and Davis: Diving Medicine, W.B. Saunders, 1990) we stated a VSD might cause a risk of arterial air embolism. In the next edition of the book, due out this year, we have removed the suggestion that small VSDs are such a risk. I have heard from a number of divers during the past five years indicating they dive safely with a small VSD.

Current wisdom is a small VSD of no hemodynamic significance is not likely to increase risk of arterial embolism. This is not true for atrial septal defect (ASD). The current medical literature on patent foramen ovale and ASD indicate there is likely to be more risk for bubbles to pass from the veins to arteries at the atrial level than was thought in the past. Other than the need to take antibiotics prior to dental procedures to avoid infection in the heart, the VSD should be of no concern to your patient if the shunt is small. (Both VSD and ASD are gaps in the wall between the right and left chambers of the heart. Blood from the veins can be diverted into the arteries through either gap but the predominant flow in both cases is from the left to the right side of the heart. However, flow through the ASD can reverse and cause bubbles in the veins to flow into the arterial circulation, while this is unlikely in a VSD.)