January 2002

Lasik and Beyond

Jim Schwiegerling

Laser-assisted in situ keratomileusis, better known as LASIK, is a surgical procedure for reducing refractive error in the eye. In this procedure, a device called a microkeratome is used to shave a thin, hinged flap in the cornea. The flap is folded back to expose the internal tissue of the cornea. Pulses from an excimer laser operating at a wavelength of 193 nm are then delivered to this tissue to modify its shape. This wavelength is used because it ablates tissue without extensive collateral damage and because it has low mutagenicity.

The Femtosecond Blade: Applications in Corneal Surgery

Surgeons use a number of devices to create incisions in tissue. These include steel and gem blades, radio frequency, high-pressure waterjet, and electrocautery technologies. Interestingly, while lasers have an established place in the operating room, as cutting tools they play a minor role. Until recently, a major limiting factor was the lack of three-dimensional precision found with each of three types of laser-tissue interaction: photocoagulation, photoablation, and photodisruption.

The Eye's Mechanisms for Autocalibration

As those of us who build optical instruments are all too aware, changes in the environment surrounding an instrument or changes within the instrument itself can quickly throw it out of calibration. This usually requires someone to intervene and restore the device to its calibrated state. The human visual system, on the other hand, does not enjoy the luxury of such a caretaker, and must calibrate itself continuously. Evolution has created ingenious mechanisms that maintain optimal visual performance over the three-quarters of a century that corresponds to a typical human lifespan.

Making the Invisible Visible: Röntgen's Mysterious X Rays

Amateur scientists who traveled from town to town in the mid-nineteenth century delighted audiences by showing them the ancestor of the neon sign: the air was pumped out of a glass tube with platinum wires embedded in opposite ends, and the interior was made to glow in lively patterns when a high voltage was run across the wires. Transfixed by the fluorescence, the lecturers had however absolutely no idea what caused the electrical excitation in the vacuum tube.


Teaching the Physics of a Diode-Pumped Laser

The Uncertainty Principle in Classical Optics

In Canada, Rural Fiber Network Sets the Pace

Uncle Sam and Auntie Trust


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