Surgery: Into the Eye with Ultrasound

Doctors in Washington last week made surgical history when they slipped an ingenious and incredibly small ultra sound probe inside a patient's eyeball for the first time and located a sliver of brass. Once found, the sliver was instantly removed, and James Cassiday, 11, was assured that he will regain substantial vision in his damaged left eye.

Chief of the operating team at Walter Reed General Hospital was Colonel Jack W. Passmore, the Army's top eye surgeon. He had taken charge of Jimmy's case two weeks earlier when the young son of an Air Force colonel had injured himself by banging on a .22-cal. blank cartridge with a hammer. Some thing from the explosion had slashed through the cornea (outer covering) of Jimmy's eye, through the dark-brown iris, through the lens and the gelatinous filler behind it, until it had come to rest just short of the retina, the screen at the back of the eyeball (see diagram). Repairing the cornea was routine. But find ing the object that had made the wound —and was still in the eyeball — was another matter. All standard techniques failed.

Cat's Eye Tests. If the object in Jimmy's eye had been of iron or steel, Colonel Passmore could have removed it with relative ease on his first try with an electromagnet. When he found that it was another material — almost certainly brass—all he could do was let the eye heal a little and hope to get at the object later. But there was grave danger that eye fluids would react with the metal and compel removal of the eye. Then Dr. Passmore remembered reading that Dr. Nathaniel Bronson II had begun work in New York on an ultrasound probe to locate foreign bodies in the eye within a millimeter. (X rays have an error range of three to four millimeters, which is considered to be too wide for an eye surgeon.)

A phone call brought the happy news that Dr. Bronson's gadget was ready for its first trial on a human patient. The engineering part of the job had been done by Philadelphia's Smith Kline Instrument Co.; Surgeon Bronson had already tried their Ekoline-20 ultrasonic probe successfully in the eyes of cats and in surgically removed human eyes. Dr. Bronson rushed to Washington to join Dr. Passmore in the precedent-making operation.

Pulses & Echoes. With Jimmy anesthetized, Dr. Passmore first rolled the left eyeball over in its socket and applied heat, to "glue" the retina in place so that it would not become detached during surgical manipulation. With an ultrasound device that worked from outside the eyeball, Dr. Bronson was able to get a rough idea where the object was, and Dr. Passmore proceeded to remove the useless, damaged lens from Jimmy's eye. Then Dr. Bronson took up the ultimate in delicate, ultrasound probes, smaller and finer than any dentist's drill. Its tip, about as thick as a pencil lead, emitted ultrasound pulses and picked up the echoes that came back from objects in their path. The time difference between pulse and echo, shown as a peak on a tiny oscilloscope (like a one-inch TV tube) held in an assistant surgeon's hand, indicated the distance of the probe's end from the object in Jimmy's eye.