Contribution of Bowman layer to corneal biomechanics.

Emilio A Torres-Netto, Farhad Hafezi, Bogdan Spiru, Francesca Gilardoni, Nikki L Hafezi, Jose Alvaro P Gomes, J Bradley Randleman, Walter Sekundo, Sabine Kling

Journal: Journal of cataract and refractive surgery 2021;47(7):927-932

PMID: 33315734

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Abstract

PURPOSE

To compare the elastic modulus of thin corneal lamellas using 2D stress-strain extensometry in healthy ex vivo human corneal lamellas with or without the presence of Bowman layer.

SETTING

Center for Applied Biotechnology and Molecular Medicine, University of Zurich, Switzerland; ELZA Institute, Dietikon, Switzerland; Department of Ophthalmology, Philipps University of Marburg, Germany.

DESIGN

Prospective experimental laboratory study.

METHODS

Healthy human corneas were stripped of Descemet membrane and the endothelium for Descemet membrane endothelial keratoplasty. After epithelium removal, corneas were divided into 2 groups. In Group 1, Bowman layer was ablated with an excimer laser (20 μm thick, 10 mm). In Group 2, Bowman layer was left intact. Then, a lamella was cut from the anterior cornea with an automated microkeratome. Elastic and viscoelastic material properties were analyzed by 2D stress-strain extensometry between 0.03 and 0.70 N.

RESULTS

Twenty-six human corneas were analyzed. The mean lamella thickness was 160 ± 37 μm in corneas with Bowman layer and 155 ± 22 μm in corneas without. No statistically significant differences between flaps with and without Bowman layer were observed in the tangential elastic modulus between 5% and 20% strain (11.5 ± 2.9 kPa vs 10.8 ± 3.7 kPa, P > .278).

CONCLUSIONS

The presence or absence of Bowman layer did not reveal a measurable difference in corneal stiffness. This may indicate that the removal of Bowman layer during photorefractive keratectomy does not represent a disadvantage to corneal biomechanics.

Address: From the Laboratory of Cell Biology, Center for Applied Biotechnology and Molecular Medicine, University of Zurich, Zurich, Switzerland (Torres-Netto, F. Hafezi, Gilardoni); Department of Ophthalmology and Visual Sciences, Paulista School of Medicine, Federal University of Sao Paulo, Sao Paulo, Brazil (Torres-Netto, Gomes); ELZA Institute, Dietikon/Zurich, Switzerland (Torres-Netto, F. Hafezi, Gilardoni); Faculty of Medicine, University of Geneva, Geneva, Switzerland (Torres-Netto, F. Hafezi); Department of Ophthalmology, University of Southern California, Los Angeles, California (F. Hafezi, N. Hafezi); Department of Ophthalmology, Wenzhou Medical University, Wenzhou, China (F. Hafezi); Department of Ophthalmology, Phillips University of Marburg, Marburg, Germany (Spiru, Sekundo); Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio (Randleman); Computer Vision Laboratory, Swiss Federal Institute of Technology, Zurich, Switzerland (Kling).

DOI: 10.1097/j.jcrs.0000000000000543

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MeSH Terms: Biomechanical Phenomena, Cornea, Germany, Humans, Photorefractive Keratectomy, Prospective Studies