April 2010
Volume 51, Issue 13
Free
ARVO Annual Meeting Abstract  |   April 2010
Feasibility of Astigmatism Correction With Selective Thermal Treatment of the Anterior Cornea
Author Affiliations & Notes
  • R. Pertaub
    Avedro Inc., Waltham, Massachusetts
  • D. Borja
    Avedro Inc., Waltham, Massachusetts
  • H. Loree
    Avedro Inc., Waltham, Massachusetts
  • D. Muller
    Avedro Inc., Waltham, Massachusetts
  • Footnotes
    Commercial Relationships  R. Pertaub, Avedro Inc., E; D. Borja, Avedro Inc., E; H. Loree, Avedro Inc., E; D. Muller, Avedro Inc., E.
  • Footnotes
    Support  None.
Investigative Ophthalmology & Visual Science April 2010, Vol.51, 4217. doi:https://doi.org/
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      R. Pertaub, D. Borja, H. Loree, D. Muller; Feasibility of Astigmatism Correction With Selective Thermal Treatment of the Anterior Cornea. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4217. doi: https://doi.org/.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract
 
Purpose:
 

To determine the feasibility of correcting low to moderate astigmatism via Keraflex (KFX), a microwave based approach to thermal keratoplasty, as evidenced by the ability to selectively induce astigmatism along a desired meridian in an ex vivo model.

 
Methods:
 

Selective heating of the cornea with a segmented annular electrode was evaluated on 17 fresh intact ex vivo porcine globes (post mortem time < 1day). Asymmetric shrinkage lesions were induced at energies of 3-8J with 2 coaxial electrodes (5mm inner dia. x 200µm thick inner electrode and a 6.5mm outer dia. ground electrode). A groove segments the inner electrode to form two C-shaped heating zones, thus selectively flattening the anterior corneal surface along a desired meridian. Pre- and post-KFX corneal radii of curvature were assessed along 32 meridians about the optical axis from cross sectional Scheimpflug slit-lamp images, from which SimK refractive power was calculated. Pre-op and induced astigmatic error (Cylinder [D]), defined as power difference between steepest and flattest perpendicular meridians, as well as the post-KFX axis of flat (AoF) were analyzed.

 
Results:
 

Selective shrinkage of the corneal stroma flattens the total corneal surface within the central 8mm pupil diameter. The post-KFX astigmatism axis of flat corresponds well to the electrode groove axis (Post-KFX AoF [deg]=0.91*Groove Axis [deg], r=0.80 and p<0.0001). The post-KFX astigmatic error increased linearly with applied energy (Cylinder [D]=2.17*Energy[J], n=21, r=0.32 and p=0.03).

 
Conclusions:
 

While KFX flattens the entire anterior cornea, the effect can be amplified along a desired meridian, adjusting both refractive power and AoF, showing promise for combined treatment of astigmatism and myopia error.  

 
Keywords: refractive surgery • astigmatism • myopia 
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