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. 2017 May 16:11:897-905.
doi: 10.2147/OPTH.S133839. eCollection 2017.

The use of WaveLight® Contoura to create a uniform cornea: the LYRA Protocol. Part 1: the effect of higher-order corneal aberrations on refractive astigmatism

Manoj Motwani  1
Affiliations

The use of WaveLight® Contoura to create a uniform cornea: the LYRA Protocol. Part 1: the effect of higher-order corneal aberrations on refractive astigmatism

Manoj Motwani. Clin Ophthalmol. .

Abstract

Purpose: To demonstrate how higher-order corneal aberrations can cancel out, modify, or induce lower-order corneal astigmatism.

Patients and methods: Six representative eyes are presented that show different scenarios in which higher-order aberrations interacting with corneal astigmatism can affect the manifest refraction. WaveLight® Contoura ablation maps showing the higher-order aberrations are shown, as are results of correction with full measured correction using the LYRA (Layer Yolked Reduction of Astigmatism) Protocol.

Results: Higher-order corneal aberrations such as trefoil, quadrafoil, and coma can create ovalization of the central cornea, which can interact with the ovalization caused by lower-order astigmatism to either induce, cancel out, or modify the manifest refraction. Contoura processing successfully determines the linkage of these interactions resulting in full astigmatism removal. Purely lenticular astigmatism appears to be rare, but a case is also demonstrated. The author theorizes that all aberrations require cerebral compensatory processing and can be removed, supported by the facts that full removal of aberrations and its linkage with lower-order astigmatism with the LYRA Protocol has not resulted in worse or unacceptable vision for any patients.

Conclusion: Higher-order aberrations interacting with lower-order astigmatism is the main reason for the differences between manifest refraction and Contoura measured astigmatism, and the linkage between these interactions can be successfully treated using Contoura and the LYRA Protocol. Lenticular astigmatism is relatively rare.

Keywords: LASIK; PRK; WaveLight Contoura; higher order aberrations; topographic guided ablation; uniform cornea.

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Conflict of interest statement

Disclosure Dr Motwani has received a grant from Alcon for a previous unrelated study. The Contoura system using the LYRA Protocol was developed by Dr Motwani in conjunction with Sissimos Lemonis of WaveLight® Lasers. The author reports no other conflicts of interest in this work.

Figures

Figure 1
Figure 1
How with-the-rule and against-the-rule create an oval-shaped central cornea. Note: The arrows show the direction of the “bowtie.”
Figure 2
Figure 2
Case 1: corneal aberration induction of manifest astigmatism. Notes: (A) Preoperative topography, (B) preoperative higher-order aberration pattern, (C) 3-month postoperator topography. Max and Cen are tissue removal numbers in microns. Max is the total amount of microns removed for higher order aberration removal, while the Cen number is the amount removed in the center of the cornea.
Figure 3
Figure 3
Case 2: corneal aberration cancellation of manifest astigmatism. Notes: (A) Preoperative topography, (B) preoperative higher-order aberration pattern, (C) 1-week postoperator topography. Max and Cen are tissue removal numbers in microns. Max is the total amount of microns removed for higher order aberration removal, while the Cen number is the amount removed in the center of the cornea.
Figure 4
Figure 4
Case 3: corneal aberration cancellation via oblique aberration and cerebral processing. Notes: (A) Preoperative topography, (B) preoperative higher-order aberration pattern, (C) 1-month postoperator topography. Max and Cen are tissue removal numbers in microns. Max is the total amount of microns removed for higher order aberration removal, while the Cen number is the amount removed in the center of the cornea.
Figure 5
Figure 5
Case 4: aberration induction of astigmatism with dilation of the pupil. Notes: (A) Preoperative topography, (B) preoperative higher-order aberration pattern with arrow pointing to peripupillary coma, (C) 1-month postoperator topography. Max and Cen are tissue removal numbers in microns. Max is the total amount of microns removed for higher order aberration removal, while the Cen number is the amount removed in the center of the cornea.
Figure 6
Figure 6
Case 5: oblique manifest astigmatism induced by corneal aberration. Notes: (A) Preoperative topography, (B) preoperative higher-order aberration pattern, (C) 1-month postoperator topography. Max and Cen are tissue removal numbers in microns. Max is the total amount of microns removed for higher order aberration removal, while the Cen number is the amount removed in the center of the cornea.
Figure 7
Figure 7
(A) Case 6: topolyzer topography of patient. (B) Case 6: Contoura surgical planning page showing higher-order aberration pattern and measured astigmatism. (C) Case 6: wavefront scan showing higher amount of astigmatism.
Figure 7
Figure 7
(A) Case 6: topolyzer topography of patient. (B) Case 6: Contoura surgical planning page showing higher-order aberration pattern and measured astigmatism. (C) Case 6: wavefront scan showing higher amount of astigmatism.
See this image and copyright information in PMC

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