Is laser vision correction unsuitable for patients with bad astigmatism?
LASIK is not necessarily unsuitable for eyes with a great deal of astigmatism, it is unsuitable for eyes with a great deal of myopia (nearsightedness) or Irregular astigmatism.
"Astigmatism" just means there is no single focal point. The most common cause for this is a cornea (the primarily focusing part of the eye) that is not perfectly symmetrical and equally curved 360˚around the line of vision. The most common kind of astigmatism is Regular astigmatism (called "cylinder"). This is the only astigmatism that can be easily corrected with glasses or soft contact lenses. LASIK is very good at correcting this.
Where things get tricky is the situation where a cornea might be irregular, i.e. not radially symmetrical. Certain excimer lasers employed in the highest quality LASIK can reduce or correct even this fairly rare type of astigmatism. But often, irregular astigmatism is associated with abnormal corneas whose structural integrity might be compromised by the thinning LASIK entails. So it is not so much how bad the astigmatism is but rather how abnormal the cornea is causing the astigmatism.
Written by J. Trevor Woodhams, M.D. - Chief of Surgery, Woodhams Eye Clinic