Surgeons will soon be able to enter the eye to carry out operations—at least in a virtual

sense. Techniques derived from virtual reality the computer system that immerses operations in an artificial computer-generated world—will allow surgeons to feel as if he could see the in side of the eye during an operation, creating the illusion that they are actually there.

Researchers at the Biorobotics (生物机械技术)Laboratory of McGill University in Montreal are building a robot , known as Micro Surgery robot-1(MSR- I for short), that will perform. delicate operations under the control of a human surgeon. The robot is specifically designed for performing eye surgery but could have other applications, such as the removal of brain tumors. The system could also be used to allow surgeons and their students to practise simulated surgery that feel like the real thing- without the real consequences for the patients.

During the operations, the surgeon manipulates a set of control known as the master. These are connected through a high- performance computer to the robot. Both the master and the robot have two limbs, When the surgeon moves the masters' limbs, the robots limbs move in exactly the same way, except that the movements can be scaled down as much as a thousand times. This will eliminate hand tremor and poor accuracy and thus reduce the damage to the eye that can occur with present microsurgery techniques. Each of the robots limbs has a minimum movement of one micrometer---more than one hundred times the precision of the human hand.

The computer also creates a three - dimensional robot' s eye view of the inside of the eye that the surgeon can see by wearing a virtual reality helmet (虚拟现实头盔) that has a small lens in front of each eye.

To provide the surgeon with such a realistic experience, MSR-I must be able to move rapidly, but this requires extremely fast computing. To handle the computational demands of instant interaction, the McGill team is constructing its own parallel-processing computer., It is al so studying areas such as muscle mechanism, artificial intelligence and optics, and has a already built another micro robot MR- I, capable of manipulating a single living cell.

Although commercial applications of the new system are not expected for several years, its basic mechanical components will be ready for testing in a few months, "The day when micro robots will be able to perform. surgery without human intervention is many years away," says Hunter, "in the meantime , a system such as MRS-I is a necessary precursor."

The so-called "virtual reality "mentioned in this passage is actually.

A．a surgical tool used for operations

B．a computer system used to produce life- like illusions

C．a new kind of applications in a visual technology.

D a way to carry out operations in a visual sense