J. Eur. Opt. Society-Rapid Publ. 2025, 21, 10 Ó The Author( s), published by EDP Sciences, 2025 https:// doi. org / 10.1051 / jeos / 2025006 Available online at: https:// jeos. edpsciences. org
Journal of the European Optical Society-Rapid Publications
RESEARCH ARTICLE Peri-operative intrastromal corneal segmentation after creation of corneal cuts based on laser induced optical breakdown: A perspective study
Masoud Mehrjoo 1,*
, Alexander Pacuraru 1, Luise Krüger 1, Florian Beck 2, Konrad Doll 2, and Samuel Arba Mosquera 1
1 SCHWIND eye-tech-solutions, Research & Development Department, 63801 Kleinostheim, Germany 2 Laboratory for the design of digital circuits and systems, University of Applied Sciences Aschaffenburg, 63743 Aschaffenburg, Germany
Received 17 December 2024 / Accepted 27 January 2025
Abstract. Refractive correction techniques, such as Lenticule Extraction and LASIK, are pivotal in corneal surgery. Precise morphological characterization is essential for identifying post-operative complications, which can be compromised by image noise and low contrast. This study introduces an automated image processing algorithm that integrates non-local denoising, the Sobel gradient method, and Bayesian optimization to accurately delineate lenticule volumes and flap surfaces. Validated on 60 ex vivo porcine eyes treated with the SCHWIND ATOS femtosecond laser, the algorithm demonstrated high accuracy compared to the manual gold standard while effectively reducing variability.
Keywords: Optical coherence tomography, Image processing, Refractive surgery, Femtosecond lasers.
1 Introduction
Refractive surgery is a broad term encompassing various surgical procedures to correct vision. The primary goal is to reduce or eliminate the need for eyeglasses or contact lenses and to enhance the visual acuity [ 1 – 3 ]. Femtosecond lasers have advanced the field of refractive surgery by enabling precise and reproducible tissue cutting, as supported by several studies( e. g., [ 4, 5 ]).
In refractive surgery, distinct substructures are created depending on the procedure. For instance, the optical breakdown procedure generates an intrastromal lenticule that is extracted through a small incision, while LASIK involves the creation of a corneal flap, followed by stromal ablation with an excimer laser. While the mechanical characteristics of the substructures differ, understanding their properties is critical for surgical outcomes.
One of the earliest applications of femtosecond lasers in refractive surgery is flap creation for LASIK. Compared to mechanical microkeratomes, femtosecond lasers offer several advantages, including a reduced risk of severe flap breaks during surgery and the ability to customize flap shape [ 6, 7 ].
Lenticule extraction is a well-established alternative for laser vision correction. This procedure uses an ultrashort pulse laser system to define the shape of a tissue
* Corresponding author: masoud. mehrjoo @ eye-tech. net volume that will be removed to achieve refractive correction [ 8, 9 ].
A precise lenticule design ensures it can be removed without damaging the surrounding tissue, thus lowering risks such as corneal dryness, infection, or refractive errors [ 10 – 12 ]. Flap dimensions such as size and thickness can influence visual recovery [ 13 ]. Flap morphology characterization can reduce potential risks of postoperative flap striae and displacements [ 14 ].
The geometry characterization of flap and lenticule cuts is an associated procedure playing a crucial role in refractive surgeries. The geometric parameters such as flap diameter and thickness are of importance for achieving the desired refractive outcomes. For instance, the semi-automated measurement of central values was studied by Lwowski et al. [ 15 ].
The geometry of lenticule cuts determines the amount of corneal tissue removed or reshaped. Accurate characterization ensures the desired refractive correction, minimizing postoperative refractive errors and enhancing predictability. Characterizing the geometry reduces the risks associated with surgical interventions as well as explaining probable post-operative issues originating from imperfect residuals. Previous systematic studies predominantly relied on manual expert assessment for geometry characterization [ 16 – 20 ]. These approaches often involved subjective interpretation and significant variability due to human factors. Consequently, they could be less consistent and
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