Does the PRK surgery solve the cylinder problems too in a case of a patient who has myopia and cylinder issues?

07 Dec Does the PRK surgery solve the cylinder problems too in a case of a patient who has myopia and cylinder issues?

LASIK and PRK both routinely treat sphero-cylinderical refractive errors (poor focus needing glasses). It would be a mistake, though, to think of sphere+cylinder as equivalent to refractive error just because the former are overwhelmingly the cause of that error .

The eye’s focus is mostly done by the anterior surface of the cornea. But the cornea is not always radially symmetrical as would have to be the case in getting it to focus perfectly with a spectacle lens or a contact lens. The cornea is actually somewhat irregular and can have less common refractive errors that are not correctable by any spectacle lens, e.g. coma and spherical aberration. This is why one person might have incredibly sharp vision (say, 20/12.5) while another person at the same time and place might see “only” 20/20. Coma and spherical aberration (along with a host of others often without a name) used to be called “Irregular Astigmatism,” but now are referred to using the same name optical physicists use: Higher Order Aberrations (HOAs).

The very best lasers in PRK/LASIK do not just carve the spectacle correction onto the cornea -they optimize the entire cornea’s surface including any HOAs. This is why we can often provide visual acuity with laser vision correction better than what glasses or contact lenses can provide.