Corneal Biomechanical Assessment using Dynamic UHS Scheimpflug Imaging

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Corneal Biomechanical Assessment using Dynamic
Ultra High-Speed (UHS) Scheimpflug Imaging and
Non-Contact Tonometry (NCT)
Diogo L. Caldas, MD Isaac C. Ramos, MD Renato
Ambrósio Jr, MD, PhD Michael W. Belin, MD,
FACS Cynthia J. Roberts, PhD
Dr. Ambrósio, Dr. Belin and Dr. Roberts are
consultants for Oculus Optikgeräte GmbH (Wetzlar,
Germany)
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Purpose

• To present CorVis ST (Oculus, Wetzlar) - a new
  clinical tool for assessment of corneal
  biomechanical properties and intraocular pressure
  (IOP)
• To test its capability to distinguish different
  materials based on their deformation
  characteristics

• Ultra High-Speed (UHS ST)
• Scheimpflug Technology 4,330 frames/sec
• 8mm horizontal coverage
• NCT symmetrically metered air pulse

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Methods Contact Lens Experiment

• Three hydrophilic contact lenses
• TAN-40 62 Hydroxyethylmethacrylate (525µm
  thick)
• TAN-58 42 Methylmethacrylate (258µm thick)
• TAN-G5X 41 Hydroxyethylmethacrylate/Glycolmetha
  crylate, (550µm thick)

• Mounted on a water chamber with adjustable
  pressures

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Methods Contact Lens Experiment

• Pressures from 0 to 70mmHg (5mmHg intervals)
• 6 measurements for each lens at each pressure
  level

MAIN OUTCOME MEASURES

• Deformation amplitude (DA- highest concavity
  displacement of the apex)
• Corneal speed and curvature
• Time for the highest concavity momentum
• Curvature at highest concavity momentum

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Response is influenced by the Pressure at the
Chamber
Contact Lens Experiment TAN 40 at 0mmHg adjusted
chamber pressure
Contact Lens Experiment TAN 40 at 20mmHg
adjusted chamber pressure

Contact Lens Experiment TAN 40 at 60mmHg
adjusted chamber pressure
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Deformation Amplitude X Pressure (hydrostatic
head)

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Results Deformation amplitude

• DA Highest concavity displacement of the apex

Contact Lens Experiment Measurements at 20mmHg
adjusted IOP

Coef. Of Variability lt 5
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Response is influenced by the Pressure at the
Chamber
TAN 40 at 0mmHg adjusted chamber pressure

TAN 58 at 60mmHg adjusted chamber pressure
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Results Highest Concavity

• Time of highest concavity momentum (HC Time)
• Curvature at highest concavity momentum (Cur HC)

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Conclusions from Contact Lens Experiment

• Dynamic UHS Scheimpflug corneal imaging with NCT
  enables to differentiate physical properties in
  test objects based on deformation response

• The response is influenced by the material
  properties and by chamber pressure

• The inspection of the actual deformation process
  provides further detailing for corneal
  characterization

• Relevance for Cornea, Refractive Surgery,
  Glaucoma

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Thank You !

diogolcaldas_at_gmail.com