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.
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.
Corneal marker Used to mark the cornea to specify the treatment pattern.
Lid speculum Attached by a cable and connector to the console, this tool serves as the return (dispersive) electrode for the RF energy being delivered through the Keratoplast™ Tip. Two types of specula are offered: the small wire type and the locking type for patients in a supine position or when the procedure is being performed under an operating microscope.
Handpiece A reusable, pen-shaped instrument that connects with the Keratoplast Tip. Also attached to the console by a cable and connector.
Keratoplast tip A single-use, micro-thin tip that is 90 µm in diameter and 450 µm long, and is attached to the handpiece that delivers the RF energy directly to the corneal stroma. This sterile tip also has a plastic stop at the very distal portion to assure the correct penetration depth.
Footpedal control A familiar and easy-to-use activation pedal for the controlled release of radiofrequency energy
from Refractec, Inc. for ViewPoint™ CK System (Conductive Keratoplasty)