How Is Laser Eye Surgery Related to Physics?
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Introduction
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Laser eye surgery refers to a handful of refractive eye surgeries that use powerful lasers to alter the shape of the cornea. The goal of refractive eye surgery (be it laser-assisted or otherwise) is to correct the way that light travels through the lens and onto the retina. Laser eye surgery draws heavily from two major areas of physics: optics and quantum mechanics.
Optics
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In physics, the branch of study known as optics deals with the behavior of electromagnetic radiation (i.e., light). Knowledge of this subject is essential understanding how the eye works, how vision can be corrected, and how lasers can focus energy so precisely.
When visible light travels through one medium (e.g., air) to another (e.g., the solid tissue of your eye), its speed changes slightly. This causes the wavelength of the photons (which compose the light) to shorten, resulting in a bending effect known as refraction. The cornea (and lens of the pupil) bend incoming light so that it lands on the retina, which sends an image to the brain via the optic nerve. Based on the cornea's size and shape, the angle of refraction it creates will be different. In the case of near-sightedness or far-sightedness, the angles of refraction created by the eye are either too great or too small for the retina, resulting in fuzzy, out-of-focus images being sent to the brain.
Through a knowledge of optics, doctors can determine the shape of the cornea that will result in optimal light refraction. The goal of laser eye surgery, therefore, is to transform the cornea accordingly.
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Quantum Physics
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Laser is an acronym for "Light Amplification by Stimulated Emission of Radiation." Basically, when atoms are excited by a continually amplified source of energy (e.g., electromagnetic, chemical, nuclear, etc.). These increased energy levels excite the electrons surrounding the atoms to move to configurations possessing greater amounts of potential energy. Sporadically, these electrons drop back to their low-potential energy configurations, releasing the excess energy as fast-moving photons of electromagnetic radiation. These photons then exit the stimulation chamber through a small opening, forming a uniform stream of high energy particle (i.e., a laser beam).
The field of quantum mechanics is concerned, in part, with the behavior of electrons and other subatomic particles at various energy states. By understanding the different energy levels (orbitals) of different atoms, scientists can predict the energy and specific frequency of light photons emitted by lasers made from those atoms. This allows doctors and clinical researchers to identify which lasers would work best for refractive eye surgery applications.
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