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The application of conductive keratoplasty for the shrinkage of the human cornea

By Τατιάνα Ναουμίδη

Abstract

The surgical correction of hyperopia and hyperopic astigmatism has always been a challenge for refractive surgeons. The efficacy, quality of vision and most im-portantly safety, provided by the existing laser surgical techniques are often not satis-factory. On the other hand, thermokeratoplasty procedures are minimally invasive, do not require corneal tissue removal, and operate outside the central clear zone of the cornea. The goal of conductive keratoplasty, which is a thermokeratoplasty technique, is to produce structural changes in the three-dimensional grating of collagen in the stroma of the cornea. These changes are achieved through the elevation of the tissue temperature. The increased tissue temperature is induced by electric impedance in the flow of energy through the collagen fibrils. Controlled-release radiofrequency energy (350 KHz) is delivered to the depth of 500 μm with the help of a Keratoplast tip ViewPoint™ CK (Refractec, Inc., Irvine, CA, USA). With the increase of the tissue temperature the collagen fibrils shrink by 30% of their original length. The application of the energy takes place in the periphery of the cornea where the increase of tempera-ture causes “corneal shrinkage” and flattening of the corneal surface, the fact that leads to a comparative increase of curvature in the central optically active part of the cornea. This new technology is currently used for the correction of low to moderate hyperopia and most recently presbyopia in patients of 45 years and older. In the course of the current study conductive keratoplasty was used to primarily treat hyper-opic astigmatism through the application of an original astigmatic nomogram. The current study reports on the results of conductive keratoplasty treatment of primary and secondary astigmatism trough the application of the original astigmatic nomogram, the safety profile of the new technique obtained trough human and animal histological studies, as well as the expansion of the existing nomogram for the spheri-cal corrections to higher degrees of hyperopia. The purpose of the current thesis is to study the shrinkage of the corneal tissue with the means of conductive keratoplasty in order to produce safe, predictable and effective treatment of low to moderate hyperopia as well as hyperopic astigmatism. In order to achieve this goal the technique was applied for the treatment of low to moderate hyperopia in individuals over 45 years of age. The safety of the treatment was evaluated through the histological studies of CK-treated human and rabbit cor-neas. The technique was applied for the treatment of higher levels of hyperopia due to the modification of the surgical technique as well as for the treatment of primary and secondary astigmatism.

Topics: Ραδιοσυχνότητες, Ρίκνωση, Κερατοειδής χιτώνας, Κερατοπλαστική, Υπερμετρωπικός αστιγματισμός, Radiofrequencies, Shrinkage, Human cornea, Conductive keratoplasty, Hyperipic astigmatism
Publisher: University of Crete (UOC)
Year: 2006
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