Golden angle based scanning for robust corneal topography with OCT

Abstract

Corneal topography allows the assessment of the cornea's refractive power which is crucial for diagnostics and surgical planning. The use of optical coherence tomography (OCT) for corneal topography is still limited. One limitation is the susceptibility to disturbances like blinking of the eye. This can result in partially corrupted scans that cannot be evaluated using common methods. We present a new scanning method for reliable corneal topography from partial scans. Based on the golden angle, the method features a balanced scan point distribution which refines over measurement time and remains balanced when part of the scan is removed. The performance of the method is assessed numerically and by measurements of test surfaces. The results confirm that the method enables numerically well-conditioned and reliable corneal topography from partially corrupted scans and reduces the need for repeated measurements in case of abrupt disturbances.

Effect of fixational eye movements in corneal topography measurements with optical coherence tomography

“…The average repeatability found experimentally in a group of young subjects was 0.09 D. In a posterior study [29], the authors demonstrated the ability of the method to estimate not only power but also astigmatism in clinical patients with variabilities of 0.17 and 0.26 D for sphere and cylinder, respectively. Wagner et al [30] proposed a scan pattern based on Fermat's spiral in which the data is obtained in a distributed way allowing distorted parts of the scan to be excluded to reconstruct the full shape of the cornea even in the presence of severe eye movements, however the repeatability was not studied. Anderson et al [14] obtained data from different points of the cornea simultaneously using a multichannel acquisition OCT and reported a repeatability on the order of 0.1 D. Other scan types such as a spiral with isotropic transverse sampling [31], Lissajous curves [32] and orthogonal raster scan patterns [33] have been proposed for retinal imaging OCT, where features in the images can help to register the data with each other.…”

Effect of fixational eye movements in corneal topography measurements with optical coherence tomography

“…The average repeatability found experimentally in a group of young subjects was 0.09 D. In a posterior study [29], the authors demonstrated the ability of the method to estimate not only power but also astigmatism in clinical patients with variabilities of 0.17 and 0.26 D for sphere and cylinder, respectively. Wagner et al [30] proposed a scan pattern based on Fermat's spiral in which the data is obtained in a distributed way allowing distorted parts of the scan to be excluded to reconstruct the full shape of the cornea even in the presence of severe eye movements, however the repeatability was not studied. Anderson et al [14] obtained data from different points of the cornea simultaneously using a multichannel acquisition OCT and reported a repeatability on the order of 0.1 D. Other scan types such as a spiral with isotropic transverse sampling [31], Lissajous curves [32] and orthogonal raster scan patterns [33] have been proposed for retinal imaging OCT, where features in the images can help to register the data with each other.…”

Optical methods for measuring corneal topography: A review

“…Because these polynomials lose orthogonality by scanning at discrete locations distributed over the cornea area, the use of certain scanning patterns directly influences the numerical conditions of the reconstruction with polynomials. Recently Wagner-Catin et al [45] proposed a scan pattern based on the golden angle where they reported the possibility of decreasing repeated measurements, due to its proposal of distributed area coverage, abrupt disturbances can be easily detected and excluded from reconstruction in order to obtain a reliable topography even in measurements acquired under non-optimal conditions.…”