These includes:
a. CONCAVE LENSES: They are known also as Minus lenses, they are used to correct shortsightedness or myopia.
b. CONVEX LENSES: They are also known as plus Minus and are used to correct hyperopia or Long sightedness.
c. CYLINDRICAL LENSES: They are lenses used to correct astigmatism.
This laser procedure involves the use of femtosecond laser or microkerotome to expose the cornea stroma and then using excimer laser to reshape the Cornea stroma inorder to improve visual acuity..
LASIK is an acronym for laser assisted in situ keratomileusis. This is a surgical procedure used to correct refractive Errors like myopia, hyperopia and astigmatism.
reference; Wikipedia