Abstract
Background: This literature review is part of a research study for aberration-correcting soft contact lenses, where wavefront aberrometry was utilised. Aim: This study was conducted as part of a postgraduate research degree by the first author with particular relevance to spherical aberrations in relation to myopia and soft contact lenses, both aberration control and non-control types. Setting: This study reports on a literature review of higher order aberrations. Methods: A comprehensive review of various databases was performed, including PubMed and Google Scholar in terms of aberration control contact lenses and particular customised contact lenses for compensation of spherical aberration in myopia, was performed. Results: Wavefront sensing and Zernike polynomials are increasingly used in optometry and ophthalmology to quantify the wavefronts for an optical system such as the eye, using either lower order (LOA) or higher order aberrations (HOA). Although other mathematical methods are available, zero, 1st and 2nd orders of the Zernike polynomial expansion are LOA. Defocus ( 2 Z0 ) and astigmatism ( − and 2 2 2 Z Z2 ) are 2nd-order modes that usually can be corrected by clinicians using ordinary sphero-cylindrical compensations such as spectacle lenses. Until recently, only LOA were easily correctable by clinicians in optometry and ophthalmology. Higher order aberrations are those modes in the third radial order, n = 3 and higher, which in the past were not correctable. However, HOA contribute to only about 7% of retinal image quality and often go unnoticed by individuals, although in some instances, for example, with keratoconus or after refractive surgery, such aberrations can become more problematic. Today, new treatments are available via specially designed or customised (to an individual) rigid or soft contact lenses that are claimed to reduce or eliminate HOA such as spherical aberration ( 4 Z0 ). Conclusion: Although such specially designed or customised contact lenses have some effect on HOA, there are conflicting reports and so further investigation of this intriguing aspect remains necessary.