Definition of Excimer laser

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Excimer laser: A laser that emits very concentrated light in the ultraviolet (UV) region of the spectrum.

Excimer lasers are used, for example, in:

• Ophthalmology -- to vaporize part of the surface layer of the cornea and thus reshape the cornea to correct refractive errors from myopia (nearsightedness), hyperopia (farsightedness), and astigmatism.
• Dermatology -- to treat psoriasis and vitiligo.

An excimer laser uses a noble-gas halide. Excimer is a chemical term that refers to a substance formed by the joining of two atoms or two molecules of the same chemical composition in an excited state; it is an excited dimer.