Corneal stromal elasticity and viscoelasticity assessed by atomic force microscopy after different cross linking protocols

Janice Dias, Vasilios F. Diakonis, Michael Lorenzo, Felipe Gonzalez, Kevin Porras, Simone Douglas, Marcel Avila, Sonia H Yoo, Noel Marysa Ziebarth

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Abstract

The purpose of this study was to evaluate elasticity and viscoelasticity in the anterior and deeper stromal regions of the cornea after cross linking with three different protocols using atomic force microscopy (AFM) through indentation. A total of 40 porcine corneas were used in this study and were divided into 4 groups (10 corneas per group): control (no treatment), Dresden (corneal epithelial debridement, riboflavin pretreatment for 30min and a 3mw/cm<sup>2</sup> for 30min UVA irradiation), accelerated (corneal epithelial debridement, riboflavin pretreatment for 30min and a 30mw/cm<sup>2</sup> for 3min UVA irradiation), and genipin (corneal epithelial debridement and submersion of anterior surface in a 1% genipin solution for 4h). Elasticity and viscoelasticity were quantified using AFM through indentation for all corneas, for the anterior stroma and at a depth of 200μm. For the control, Dresden, accelerated, and genipin groups, respectively, the average Young's modulus for the anterior stromal region was 0.60±0.58MPa, 1.58±1.04MPa, 0.86±0.46MPa, and 1.71±0.51MPa; the average for the 200μm stromal depth was 0.08±0.06MPa, 0.08±0.04MPa, 0.08±0.04MPa, and 0.06±0.01MPa. Corneas crosslinked with the Dresden protocol and genipin were significantly stiffer than controls (p<0.05) in the anterior region only. For the control, Dresden, Accelerated, and genipin groups, respectively, the average calculated apparent viscosity for the anterior stroma was 88.2±43.7kPa-s, 8.3±7.1kPa-s, 8.1±2.3kPa-s, and 9.5±3.8kPa-s; the average for the 200μm stromal depth was 35.0±3.7kPa-s, 49.6±35.1kPa-s, 42.4±17.6kPa-s, and 41.8±37.6kPa-s. All crosslinking protocols resulted in a decrease in viscosity in the anterior region only (p<0.05). The effects of cross-linking seem to be limited to the anterior corneal stroma and do not extend to the deeper stromal region. Additionally, the Dresden and genipin protocols seem to produce a stiffer anterior corneal stroma when compared to the accelerated protocol.

Original languageEnglish (US)
Pages (from-to)1-5
Number of pages5
JournalExperimental Eye Research
Volume138
DOIs
StatePublished - Sep 1 2015

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Atomic Force Microscopy
Elasticity
Cornea
Debridement
Corneal Stroma
Riboflavin
Viscosity
Elastic Modulus
Immersion
genipin
Swine
Control Groups

Keywords

  • Atomic force microscopy
  • Cornea crosslinking
  • Corneal elasticity
  • Corneal viscoelasticity
  • Ultraviolet light

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience

Cite this

Corneal stromal elasticity and viscoelasticity assessed by atomic force microscopy after different cross linking protocols. / Dias, Janice; Diakonis, Vasilios F.; Lorenzo, Michael; Gonzalez, Felipe; Porras, Kevin; Douglas, Simone; Avila, Marcel; Yoo, Sonia H; Ziebarth, Noel Marysa.

In: Experimental Eye Research, Vol. 138, 01.09.2015, p. 1-5.

Research output: Contribution to journalArticle

Dias, Janice ; Diakonis, Vasilios F. ; Lorenzo, Michael ; Gonzalez, Felipe ; Porras, Kevin ; Douglas, Simone ; Avila, Marcel ; Yoo, Sonia H ; Ziebarth, Noel Marysa. / Corneal stromal elasticity and viscoelasticity assessed by atomic force microscopy after different cross linking protocols. In: Experimental Eye Research. 2015 ; Vol. 138. pp. 1-5.
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abstract = "The purpose of this study was to evaluate elasticity and viscoelasticity in the anterior and deeper stromal regions of the cornea after cross linking with three different protocols using atomic force microscopy (AFM) through indentation. A total of 40 porcine corneas were used in this study and were divided into 4 groups (10 corneas per group): control (no treatment), Dresden (corneal epithelial debridement, riboflavin pretreatment for 30min and a 3mw/cm2 for 30min UVA irradiation), accelerated (corneal epithelial debridement, riboflavin pretreatment for 30min and a 30mw/cm2 for 3min UVA irradiation), and genipin (corneal epithelial debridement and submersion of anterior surface in a 1{\%} genipin solution for 4h). Elasticity and viscoelasticity were quantified using AFM through indentation for all corneas, for the anterior stroma and at a depth of 200μm. For the control, Dresden, accelerated, and genipin groups, respectively, the average Young's modulus for the anterior stromal region was 0.60±0.58MPa, 1.58±1.04MPa, 0.86±0.46MPa, and 1.71±0.51MPa; the average for the 200μm stromal depth was 0.08±0.06MPa, 0.08±0.04MPa, 0.08±0.04MPa, and 0.06±0.01MPa. Corneas crosslinked with the Dresden protocol and genipin were significantly stiffer than controls (p<0.05) in the anterior region only. For the control, Dresden, Accelerated, and genipin groups, respectively, the average calculated apparent viscosity for the anterior stroma was 88.2±43.7kPa-s, 8.3±7.1kPa-s, 8.1±2.3kPa-s, and 9.5±3.8kPa-s; the average for the 200μm stromal depth was 35.0±3.7kPa-s, 49.6±35.1kPa-s, 42.4±17.6kPa-s, and 41.8±37.6kPa-s. All crosslinking protocols resulted in a decrease in viscosity in the anterior region only (p<0.05). The effects of cross-linking seem to be limited to the anterior corneal stroma and do not extend to the deeper stromal region. Additionally, the Dresden and genipin protocols seem to produce a stiffer anterior corneal stroma when compared to the accelerated protocol.",
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AU - Diakonis, Vasilios F.

AU - Lorenzo, Michael

AU - Gonzalez, Felipe

AU - Porras, Kevin

AU - Douglas, Simone

AU - Avila, Marcel

AU - Yoo, Sonia H

AU - Ziebarth, Noel Marysa

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