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Introduction to Wavefront Science

  • Mazen M. Sinjab
  • Arthur B. Cummings
Chapter

Abstract

Optical wavefront science is the photophysical description of optical perfection or imperfection. Understanding the principles of optical wavefront is essential for understanding its application, especially in customized laser vision correction (CLVC). The principal of wavefront measurement is the difference (deviation) between the actual wavefront shape of the measured surface and the ideal flat shape. This deviation is known as a wavefront aberration.

There are three types of aberrations: constant, lower order (LOAs) and higher order aberrations (HOAs). The constant aberrations exist in all optical systems. The LOAs are encountered with sphero-cylindrical refractive errors. HOAs are found in irregular optical systems.

Aberrations are measured by corneal and whole-eye wavefront aberrometers. There are three types of aberrometers: outgoing reflective, ingoing reflective and ingoing feedback aberrometers. There are several factors affecting the measurements, such as pupil size, accommodation, age, ocular pathologies and previous ocular surgeries. Aberrations can be measured at the pupillary level or at the retinal level. The root mean square (RMS) is the most common metric to quantify aberrations. There are other metrics that describe aberrations, such as point spread function (PSF), Strehl Ratio (SR), Modulation Transfer Function (MTF), Phase transfer function (PTF), optical transfer function (OTF), Zernike coefficient and Fourier Analysis. The last two are the most commonly used, and each of them has its advantages.

In addition to qualification and quantification of aberrations, there are several clinical applications of wavefront technology. It is applied in the prediction of subjective refraction, detection of forme fruste keratoconus, wavefront optimized and wavefront guided laser ablation profiles, intraocular lens design and presbyopia treatment.

As wavefront technology is applied in treatment, there are preoperative and intraoperative key factors required to achieve the desired results. The preoperative factors are wavefront capture, which must be valid, repeatable, and reproducible, precise manifest refraction, pupillometry, skillful data analysis, laser profile creation and patient counseling. The intraoperative factors are alignment and registration, centration, eye tracking, nomogram adjustment, flap creation and treatment zone.

Keywords

Wavefront Aberrations Point spread function PSF Strehl ratio SR Modulation transfer function MTF Phase transfer function PTF Optical transfer function OTF Zernike coefficient and Fourier analysis Root mean square RMS 

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Copyright information

© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  • Mazen M. Sinjab
    • 1
  • Arthur B. Cummings
    • 2
  1. 1.Damascus UniversityDamascusSyria
  2. 2.Wellington Eye ClinicDublinIreland

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