Glasses and contact lenses correct myopia, hyperopia, astigmatism and presbyopia. These optical defects are known as ‘Lower Order Aberrations’.

All eyes also have ‘Higher Order Aberrations’ which cannot be corrected by glasses or contact lenses. In other words, most people in the normal population have 20/20 vision (Quantity of Vision), but still have visual aberrations such as ghosting and halos (Quality of Vision). The correction of these ‘Higher Order Aberrations’ is discussed in the section on Custom Wavefront Lasik