Klinik für Augenheilkunde

Research Focus

The mechanical stability of the cornea is essential for maintaining its shape and optical quality. Altered biomechanics play a key role in ectatic disorders such as keratoconus and have a major impact on the outcomes of refractive procedures including LASIK and SMILE. Understanding these biomechanical changes requires experimental approaches that closely reproduce physiological conditions.

Our group investigates corneal stiffness, viscoelasticity, strain behavior, and the influence of intraocular pressure using experimental techniques such as nanoindentation, as well as clinically established devices including the Corvis ST. Applying adjustable retrocorneal fluid pressure to mimic intraocular pressure an restore physiological pretension in the tissue allows us to simulate physiological conditions during measurement, enabling highly translational insights into pre- and post-operative biomechanics in corneal crosslinking and refractive surgery. We are grateful for the collaboration with the Lions Hornhautbank Baden-Württemberg, which provides us with donor tissue if it is unsuitable for transplantation (e.g. due to an insufficient number of endothelial cells) and informed consent for research use was given.

Ongoing Projects

• Ex vivo experimental analysis of corneal biomechanics under near-physiological conditions.
• Methodological refinement of ex vivo measurement techniques.
• Influence of physiological factors on corneal biomechanics (e.g., hydration, pressure).
• Biomechanical effects of therapeutic interventions (crosslinking, refractive surgery).
• Integration of experimental data with clinical diagnostic technologies to better understand how laboratory findings translate to in vivo measurements.

Doctoral or Master's Thesis

Students interested in pursuing a doctoral or master's thesis are invited to contact Prof. Schlunck (Guenther.Schlunck@uniklinik-freiburg.de) or Dr. Touirssa (othmane.touirssa@uniklinik-freiburg.de).

Publications of the Biomechanics Group

• Bimodal ex vivo biomechanical characterization of corneal UVA-crosslinking via optical coherence elastography and nanoindentation under physiological conditions. Lohmüller R, Frigelli M, Schlunck G, Kling S, Büchler P, Reinhard T, Lang SJ. Exp Eye Res. 2025 Dec;261:110664. doi: 10.1016/j.exer.2025.110664. Epub 2025 Sep 24. PMID: 41005610.
• Nanoindentation under retrocorneal pressure to determine the biomechanical response of the human cornea to accelerated UVA crosslinking and riboflavin osmolarity ex vivo. Lohmüller R, Schlunck G, Bressler B, Böhringer D, Reinhard T, Lang SJ. Sci Rep. 2025 Oct 21;15(1):36509. doi: 10.1038/s41598-025-24522-6. PMID: 41120701; PMCID: PMC12540769.
• Multi-Modal Evaluation of Corneal Biomechanics Integrating Optical Coherence Elastography, Nanoindentation, and Uniaxial Tensile Testing. Robert Lohmüller, Matteo Frigelli, Gunther R Schlunck, Thomas Reinhard, Sabine Kling, Philippe Büchler, Stefan Lang; Invest. Ophthalmol. Vis. Sci. 2024;65(7):2050.
• Influence of different UVA-crosslinking protocols on biomechanical properties of human corneas measured ex vivo using spatially resolved nanoindentation under physiological conditions. Robert Lohmüller, Gunther R Schlunck, Thomas Reinhard, Stefan J. Lang; Invest. Ophthalmol. Vis. Sci. 2023;64(8):1682.
• Characterization of the Immediate and Delayed Biomechanical Response to UV-A Crosslinking of Human Corneas. Ross AKM, Schlunck G, Böhringer D, Maier P, Eberwein P, Reinhard T, Lang SJ. Cornea. 2023 Sep 1;42(9):1163-1171. doi: 10.1097/ICO.0000000000003336. Epub 2023 Jun 19. PMID: 37335854.
• Keratokonus: Biomechanik ex vivo. Lohmüller R, Böhringer D, Maier PC, Ross AK, Schlunck G, Reinhard T, Lang SJ. Klin Monbl Augenheilkd. 2023 Jun;240(6):774-778. German. doi: 10.1055/a-2062-3633. Epub 2023 May 5. PMID: 37146635.
• Indentation of the cornea: A Bi-layer contact problem. Swain MV, Schroeter N, Nohava J, Eberwein P. J Mech Behav Biomed Mater. 2021 Jun;118:104463. doi: 10.1016/j.jmbbm.2021.104463. Epub 2021 Mar 19. PMID: 33765544.
• Instrumented indentation for determination of mechanical properties of human cornea after ultraviolet-A crosslinking. Nohava J, Swain M, Lang SJ, Maier P, Heinzelmann S, Reinhard T, Eberwein P.  J Biomed Mater Res A. 2018 May;106(5):1413-1420. doi: 10.1002/jbm.a.36337. Epub 2018 Feb 8. PMID: 29318768.

Collaborators

• Prof. Dr. Stefan J. Lang, FEBO, MBA, 
  (former principal investigator; Director of the Dept. of Ophthalmology, University Hospital Brandenburg, Brandenburg)
• Prof. Dr. Philippe Büchler, University of Bern, ARTORG Center for Biomedical Engineering Research, Bern, Switzerland.