Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2020 Aug 12:14:2319-2327.
doi: 10.2147/OPTH.S263896. eCollection 2020.

Biomechanical Changes to the Cornea from LASIK Flap Creation Resulting in Inaccurate Ablations and Suboptimal Refractive Outcomes with Topographic-Guided Ablation

Manoj Motwani  1
Affiliations

Biomechanical Changes to the Cornea from LASIK Flap Creation Resulting in Inaccurate Ablations and Suboptimal Refractive Outcomes with Topographic-Guided Ablation

Manoj Motwani. Clin Ophthalmol. .

Abstract

Purpose: This study documents a biomechanical corneal change related to corneal flap creation in certain patients leading to an irregular ablation pattern and an inaccurate refractive outcome.

Methods: This retrospective study included consecutive eyes treated with primary LASIK Contoura using the LYRA Protocol. All LASIK procedures were performed on the WaveLight EX500 excimer laser. Flaps were created with either the Alcon WaveLight FS200 femtosecond laser or the Moria M2 microkeratome. Eyes that were off by greater than or equal to 0.50 diopters (D) sphere or cylinder from the targeted goal within 3 months after surgery were identified. Topographical, higher order aberration, and epithelial maps were created. Of these eyes, approximately 10% of eyes were found to have undergone a biomechanical change upon flap creation that led to an inaccurate outcome.

Results: Six representative cases are presented that demonstrate the biomechanical change, outcomes, and treatment. All patients demonstrated an elliptical, irregular ablation pattern on post-operative topography, lateralized the thinnest point of the cornea relative to the corneal apex on Pentacam pachymetry maps, and irregular corneal epithelial thickening at the periphery of the elliptical ablation.

Conclusion: A biomechanical change during flap creation can occur in certain types of corneas during LASIK flap creation and subsequent treatment with topographic-guided ablation leading to an irregular ablation and suboptimal refractive outcomes.

Keywords: LASIK; corneal epithelium; femtosecond laser; higher order aberration; laser ablation; laser in-situ keratomileusis.

PubMed Disclaimer

Conflict of interest statement

Dr. Motwani has received a grant from Alcon for a previous unrelated study in 2017. Dr. Motwani received non-financial support from Optovue, Inc. (loan of Optovue Avanti, clinical support in understanding analysis of data). Dr. Motwani has a patent pending on a theoretical device that could combine corneal HOA data and epithelial thickness data to achieve a more accurate refractive outcome. The author reports no other potential conflicts of interest for this work.

Figures

Figure 1
Figure 1
(A and B) Case 1. Pre-op topography and Pentacam pachymetry map. Note the lateralized central thin point relative to the apex, and pre-operative astigmatism. (C) Case 1. Pre-op OCT pachymetry and ETM. Overall relatively regular central epithelial thickness. (D) Case 1. 5 months post-op topography. Note the elliptical, irregular ablation pattern. (E) Case 1. 5 months post-op OCT pachymetry and ETM. Note the irregular thickening of the epithelium at the periphery of the ellipse. (F) Case 1. 2 months post-enhancement topography.
Figure 2
Figure 2
(A and B) Case 2. Pre-op topography. Note the lateralized thinnest point of cornea relative to the apex, and the pre-operative astigmatism. (C) Case 2. Pre-Op OCT pachymetry and ETM. Note the regular, mild variation of epithelial thickness. (D) Case 2. 5 months post-op. Note the elliptical irregular ablation. (E) Case 2. 5 Month Post Pachymetry and ETM. Note the irregular thickening of the epithelium at the periphery of the ellipse. (F) Case 2. 3 months post-enhancement.
Figure 3
Figure 3
(A and B) Case 3. Pre-op Topography and Pentacam pachymetry. Note the lateralized thinnest point of cornea relative to the apex, and the pre-operative astigmatism. (C) Case 3. Pre-Op OCT Pachymetry and ETM. (D) Case 3. 5 month post-op. Note the elliptical, irregular ablation pattern. (E) Case 3. 5 Month Pachymetry and ETM. Note the irregular thickening of the epithelium of the elliptical. (F) Case 3. 3 months post enhancement. Enhancement done via topographic-guided ablation. Notice the smooth, round, more regular ablation pattern.
Figure 4
Figure 4
(A and B) Case 4. Pre-op topography and Pentacam pachymetry. Note the lateralized thinnest point of cornea relative to the apex, and the pre-operative astigmatism. (C) Case 4. Pre-Op OCT Pachymetry and ETM. Note the relatively regular central epithelial thickness. (D) Case 4. 5 months post-op. Note the elliptical, irregular ablation pattern. (E) Case 4. 5 Month Post Pachymetry and OCT. Note the irregular epithelial thickening at the periphery of the ellipse. (F) Case 4. 8 months post enhancement.
Figure 5
Figure 5
(A and B) Case 5. Pre-op topography and Pentacam pachymetry. Note the lateralized thinnest point of cornea relative to the apex. This is lateralized less than some of the other cases. The astigmatism here is also more irregular appearing, and the irregularity does correlate with the lateralized thin point. (C) Case 5. Pre-op OCT pachymetry and ETM. Note the relatively regular central epithelial thickness. (D) Case 5. 3 months post-op. Note the elliptical, irregular ablation pattern. (E) Case 5. 3 Month Post Pachymetry and OCT. Note the irregular epithelial thickening at the periphery of the ellipse. (F) Case 5. 4 months post enhancement.
Figure 6
Figure 6
(A and B) Case 6. Pre-op topography and Pentacam pachymetry. Note the lateralized thinnest point of cornea relative to the apex, and the pre-operative astigmatism. (C) Case 6. Pre-op OCT pachymetry and ETM. Note the relatively regular central epithelial thickness. (D) Case 6. 2 months post-op. Note the elliptical shape and irregular ablation. (E) Case 6. 2 Month Post Pachymetry and OCT. Note the irregular epithelial thickening at the periphery of the ellipse. (F) Case 6. 10 months post enhancement. Note here that the elliptical shape is more exaggerated than 2 months post-op primary procedure likely due to continued epithelial thickening at the elliptical periphery.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

References

    1. Roberts C. Biomechanics of the cornea and wavefront-guided laser refractive surgery. J Refract Surg. 2002;18(5):S589–592. - PubMed
    1. Roberts C. Biomechanical customization: the next generation of laser refractive surgery. J Cataract Refract Surg. 2005;31(1):2–5. doi:10.1016/j.jcrs.2004.11.032 - DOI - PubMed
    1. Schein OD. The measurement of patient-reported outcomes of refractive surgery: the refractive status and vision profile. Trans Am Ophthalmol Soc. 2000;98:439–469. - PMC - PubMed
    1. Motwani M. The use of WaveLight® Contoura to create a uniform cornea: the LYRA protocol. Part 3: the results of 50 treated eyes. Clin Ophthalmol. 2017;11:915–921. doi:10.2147/OPTH.S133841 - DOI - PMC - PubMed
    1. Motwani M. The use of WaveLight® Contoura to create a uniform cornea: the LYRA protocol. Part 2: the consequences of treating astigmatism on an incorrect axis via excimer laser. Clin Ophthalmol. 2017;11:907–913. doi:10.2147/OPTH.S133840 - DOI - PMC - PubMed