Wavefront Aberrometry

Innovative Eye Care’s Hutt Street practice is the first Optometry practice in the world to own a Pentacam AXL Wave. One of the incredible uses of this piece of equipment is wavefront aberrometry. The Pentacam AXL Wave’s wavefront aberrometry revolutionises the management of hyperopia, myopia, astigmatism, keratoconus, and contact lens design.

What is wavefront aberrometry?

Our eyes are not perfect optical systems, as biological tissue, so everyone has some degree of aberration. Optical aberration is the deviation of a single ray of light from a point of focus.1 Wavefront aberrometry measures many rays of light to create a collective wavefront. The wavefront can then be broken down mathematically into a series of known orders of shape into what is known as a Zernike polynomial.2

The wavefront shapes are commonly simple, such as a sphere or cylinder. These simple shapes are known as lower-order aberrations and are easily corrected by spectacles and contact lenses.1 However, it’s the less common wavefront shapes that make up higher-order aberrations, such as coma and trefoil. Higher-order aberrations are responsible for common visual symptoms like glare, haloes, poor night vision and doubling.3 They are more severe in conditions like keratoconus, pterygium, and corneal graft, and cannot be totally improved with conventional optical correction.4,5

Lower-order aberrations (defocus and astigmatism) and higher-order aberrations (coma) forming the total wavefront.

How does wavefront aberrometry work?

A Hartmann-Shack wavefront sensor detects the deviation of light at hundred of points through the pupil.2 Coupled with this measurement of the total eye aberration, the Pentacam AXL Wave also uses Scheimpflug imaging to measure the shape of the front and back surface of the cornea. Both total eye aberration and corneal tomography combined can identify the source of aberration as either corneal or internal.

Visual performance of a patient’s optical system (eye) based on aberrometry readings, divided into corneal and internal components.

How can aberrometry benefit me?

Now that Innovative Eye Care is armed with the Pentacam AXL Wave, we can completely individualise the management of our patients. The ultimate aim is to correct all aberrations, creating a perfect optical system for a singular point of focus. In conditions such as keratoconus, which are known to cause large amounts of higher-order aberration, we can now measure and correct these aberrations with wavefront-guided scleral contact lenses. Furthermore, in some cases we can utilise aberrations to create a multifocal effect (multiple points of focus), or even control myopia progression in children (peripheral retinal focus confusion).6


References
  1. Maeda, N., 2009. “Clinical applications of wavefront aberrometry - a review.” Clinical and Experimental Ophthalmology, 37(1): pp.118-129.
  2. Salés, C. and E. Manche (2015). “Comparison of ocular aberrations measured by a Fourier-based Hartmann-Shack and Zernike-based Tscherning aberrometer before and after laser in situ keratomileusis.” J Cataract Refract Surg 41(1): 1820-1825.
  3. Ohlendorf, A., et al., 2020. “Advancing Digital Workflows for Refractive Error Measurements.” Journal of Clinical Medicine, 9(1): pp.2205.
  4. Jinabhai, A. (2019). “Custominsed aberration-controlling corrections for keratoconic patients using contact lenses.” Clin Exp Optom 103(1): 31-43.
  5. Kumar, P., et al. (2019). “Do visual performance and optical quality vary across different contact lens correction modalities in keratoconus?” Contact Lens and Anterior Eye, S1367-0484(20): 30052-30057.
  6. Hoy, L., 2019. “Demystifying Corneal Reshaping With Ortho-K.” Lecture for CCLSA Victoria.