Dr. Hummel - Vision Blog

The shape of the cornea (clear front part) is what a LASIK treatment works on. LASIK, whether Traditional or Custom, changes the cornea’s shape. If you are nearsighted, the cornea is too steeply curved. If you are farsighted, it’s too flat. If you are astigmatic, it’s too irregular.

Being a transparent, curved structure, the cornea bends light. The lens, behind the iris, is also a transparent, curved structure, and bends the incoming light further as it travels to the retina at the back of the eye (the “camera film”). If the cornea’s curvature is too steep, a LASIK treatment will flatten it, so that it will bend light rays a little less. Now the light will come to a focus right on the retina and you will see clearly.

If the cornea is too flat, the LASIK laser will steepen it, so it will bend light rays a little more. If the cornea is irregular in shape like a football instead of a soccer ball, LASIK will make it rounder so that light will have only one focus, instead of several.

So these are the three vision problems correctible by LASIK: myopia (nearsightedness), hyperopia (farsightedness) and astigmatism. The LASIK laser changes corneal curvature by vaporizing tiny pieces of tissue from pre-planned, precise places, according to what your vision problem is.

If you are starting to use reading glasses, you have presbyopia, and this is not treatable by LASIK. It isn’t caused by the corneal shape, but by a growing stiffness in the lens.