Very short pulses of high-intensity laser beams are used to repair detached portions of the retina of the eye. the brief pulses of energy absorbed by the retina weld the detached portion back into place. in one such procedure, a laser beam has a wavelength of 810 nm and delivers 275 mw of power spread over a circular spot 108 μm in diameter. the vitreous humor (the transparent fluid that fills most of the eye) has an index of refraction of 1.34.