ViewPoint CK System (Conductive Keratoplasty)

Hyperopic Indications
The Refractec ViewPoint CK System is for the temporary reduction of spherical hyperopia in patients who have 0.75 D to 3.25 D of cycloplegic spherical hyperopia, less than or equal to 0.75 D of refractive astigmatism (minus cylinder format), and a cycloplegic spherical equivalent of +0.75 D to +3.00 D. Patients must be 40 years of age or greater with a documented stability of refraction for the prior 12 months, as demonstrated by a change of less than 0.50 D in spherical and cylindrical components of manifest refraction. The magnitude of correction with this treatment diminishes over time, with some patients retaining some or all of their intended refractive correction.

NearVision CK builds upon the principles of thermokeratoplasty, using radiofrequency (RF) energy to temporarily reshape the cornea and therefore adjust its refractive characteristics.

RF energy and its application
To perform the procedure, a handpiece with a Keratoplast™ Tip delivers controlled RF energy directly to the internal corneal tissue in a ring pattern. The tip serves as an RF antenna while the speculum holding the eye open serves as the return path. By applying RF energy to the tissue, Ohm's law (V = I R) defines a consistent relationship that determines the heat generated. The voltage (V) determines the electrical field strength within the tissue while the current (I) is defined by the treatment parameters. Impedance is a characteristic of tissue.

The characteristics of the energy (i.e., current, waveform, frequency, rep rate and crest factor) and the tissue's consistent conductive properties make it possible for CK to achieve a reproducible, optimal tissue temperature for the critical time necessary to bring about the localized shrinkage of the collagen fibers.

Depth of procedure and effects
CK creates a purse-string effect that steepens the central cornea through a ring of application spots around the periphery of the cornea. Several studies have concluded that the depth of shrinkage determines the degree of corneal correction permanency. Because of the intrastromal delivery of RF energy, CK produces collagen shrinkage that encompasses 80% of the corneal thickness.