This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cornea and sclera, Subject name: Ophthalmology
The wavelength of the excimer laser used for corneal refractive surgery is 
Select and explain. 
A. 190nm, B. 191 nm, C. 193 nm, D. 195 nm
C: 193 nm
Answer: C: 193 nm 
Explanation: All clinical excimer lasers use are argon-fluorine (ArF) gas. The wavelength is in the UV region (193 nm), which has been determined to be safe for human ocular use.Therapeutic applications of excimer lasers are: photorefractive keratectomy (PRK), laser-assisted in-situ keratomileusis (LASIK) for correction of refractive errors and phototherapeutic keratectomy (PTK) for corneal diseases such as band-shaped keratopathyRef: Khurana; 4th ed; Page no: 431