History of the Shack Hartmann wavefront sensor and its impact in ophthalmic optics

The cornea is the outermost surface of the eyeball; and has almost 70% of the eyes total refractive power, what makes it essential for the human vision process. However, some pathologies and refractive errors modify normal functions of the cornea, decreasing visual acuity along with the individual's quality of life. Thus, in the presence of ametropia, an appropriate diagnosis, treatment, and corrections of cornea's dimensions is vital. Nowadays, several methods to retrieve corneal topography are available. In this paper, the most relevant techniques in the field are presented.

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“…A variant of this test is known as Hartman-Shack [81]. Developed for defense purposes during the cold war by Roland Shack.…”

Section: B Pattern Reflectionmentioning

confidence: 99%

Optical methods for measuring corneal topography: A review

Jalife-Chavira¹,

Trujillo-Shiaffino²,

Mendoza-Villegas³

et al. 2019

Opt. Pura Apl.

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“…This technique was used to test the optics of the "Great Refractor" telescope. 1 Later, in 1971, Platt and Shack proposed using a lenticular screen instead of using the screen constructed by Hartmann, but using the same principle, as illustrated in Figure 1.…”

Section: Introductionmentioning

confidence: 99%

Characterization of a Shack-Hartmann type wavefront sensor for its use in an experimental aberrometer

Medina Coca,

Sánchez Valencia,

Diaz Gonzalez

et al. 2023

Infrared Sensors, Devices, and Applications XIII

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The aim of this work is the characterization of a Shack-Hartmann wavefront sensor prototype through a statistical analysis in accordance with the official Mexican standard. To determine the repeatability and reproducibility of ophthalmic aberration measurements, given in Zernike polynomials, a measurement protocol was proposed. The measurements were obtained using an experimental optical system, which uses a super luminescent diode (SLD) IR, as well as ophthalmic trial lenses to introduce optical aberrations, which are used as reference materials. The complete optical system is intended to be used as an experimental aberrometer to obtain low order aberrations of the human eye in vivo.

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“…To date, a large number of studies have focused on improving the center of gravity (CoG) method [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ], but, if the aberration to be measured is too large and the fluctuation of the wavefront is too steep, it will cause some sub-aperture spots to deviate from the corresponding sub-aperture. This condition is commonly measured in patients with severe refractive errors and patients who have undergone corneal or lens surgery [ 17 , 18 ]. Carmen Canovas and Erez N. Ribak compared and analyzed SHWFS methods (convolution, interpolation, Fourier methods, and centroid methods) for ophthalmology, and found that the Fourier method has the best effect for pupils with a small slope of the boundary or with a large distance from the boundary [ 19 ].…”

Section: Introductionmentioning

confidence: 99%

A Method Used to Improve the Dynamic Range of Shack–Hartmann Wavefront Sensor in Presence of Large Aberration

Yang

Wang

2022

Sensors

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With the successful application of the Shack–Hartmann wavefront sensor in measuring aberrations of the human eye, researchers found that, when the aberration is large, the local wavefront distortion is large, and it causes the spot corresponding to the sub-aperture of the microlens to shift out of the corresponding range of the sub-aperture. However, the traditional wavefront reconstruction algorithm searches for the spot within the corresponding range of the sub-aperture of the microlens and reconstructs the wavefront according to the calculated centroid, which leads to wavefront reconstruction errors. To solve the problem of the small dynamic range of the Shack–Hartmann wavefront sensor, this paper proposes a wavefront reconstruction algorithm based on the autocorrelation method and a neural network. The autocorrelation centroid extraction method was used to calculate the centroid in the entire spot map in order to obtain a centroid map and to reconstruct the wavefront by matching the centroid with the microlens array through the neural network. This method breaks the limitation of the sub-aperture of the microlens. The experimental results show that the algorithm improves the dynamic range of the first 15 terms of the Zernike aberration reconstruction to varying degrees, ranging from 62.86% to 183.87%.

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History of the Shack Hartmann wavefront sensor and its impact in ophthalmic optics

Cited by 10 publications

References 15 publications

Optical methods for measuring corneal topography: A review

Optical methods for measuring corneal topography: A review

Characterization of a Shack-Hartmann type wavefront sensor for its use in an experimental aberrometer

A Method Used to Improve the Dynamic Range of Shack–Hartmann Wavefront Sensor in Presence of Large Aberration

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