In 2004, conductive keratoplasty (CK) received US Food and Drug Administration (FDA) approval for treatment of presbyopia in the nondominant eye of a patient with an endpoint of –1.00 to –2.00 D. The nonablative, collagen-shrinking effect of CK is based on the delivery of radiofrequency energy through a fine conducting tip that is inserted into the peripheral corneal stroma (Fig 7-1). As the current flows through the tissue surrounding the tip, resistance to the current creates localized heat. Collagen lamellae in the area surrounding the tip shrink in a controlled fashion and form a column of denatured collagen. The shortening of the collagen fibrils creates a band of tightening and flattening in the periphery that increases the relative curvature of the central cornea.
For the treatment of hyperopia, the surgeon inserts the tip into the stroma in a ring pattern around the peripheral cornea. The number and location of spots determine the amount of refractive change, with an increasing number of spots and rings used for higher amounts of hyperopia. The CK procedure is performed using topical anesthesia and typically takes less than 5 minutes. The collagen shrinkage leads to visible striae between the treated spots, which fade with time (Fig 7-2). The treatment is not advised for use in patients who have undergone radial keratotomy, and it is not FDA approved for such use.
Figure 7-1 Schematic representation of an eye undergoing conductive keratoplasty, which delivers radiofrequency energy to the cornea through a handheld probe inserted into the peripheral cornea.
(Courtesy of Refractec, Inc.)
Figure 7-2 One month after a 24-spot conductive keratoplasty treatment in a patient with +2.00 D hyperopia, the spots are beginning to fade. Three sets of 8 spots each were applied at a 6.0-, 7.0-, and 8.0-mm optical zones.
(Courtesy of Refractec, Inc.)
Despite initial reports of refractive stability, long-term follow-up has revealed regression and/or lack of adequate effect with CK. In a long-term (mean, 73.1 months; range, 44–90 months) follow-up of patients enrolled in the phase 3 multicenter trial of CK, Ehrlich and Manche found nearly complete regression of treatment effect in the 16 eyes (of the original 25 eyes) available for follow-up.
Ehrlich JS, Manche EE. Regression of effect over long-term follow-up of conductive keratoplasty to correct mild to moderate hyperopia. J Cataract Refract Surg. 2009;35(9):1591–1596.
Kymionis GD, Kontadakis GA, Naoumidi TL, Kazakos DC, Giapitzakis I, Pallikaris IG. Conductive keratoplasty followed by collagen cross-linking with riboflavin-UV-A in patients with keratoconus. Cornea. 2010;29(2):239–243.
McDonald MB. Conductive keratoplasty: a radiofrequency-based technique for the correction of hyperopia. Trans Am Ophthalmol Soc. 2005;103:512–536.
Other potential off-label uses exist for CK. In cases of overcorrected myopic LASIK and myopic photorefractive keratectomy (PRK), CK can be used to correct hyperopia. In these procedures, CK obviates the need to lift or cut another flap. CK may also be used to treat keratoconus and post-LASIK ectasia. Although in 1 report corneal irregularities improved immediately, with some improvement in visual acuity, some cases showed regression of effect at 1 month.
Combination therapy with CK plus CCL may be effective in achieving a change in corneal curvature that does not regress with time.
Alió JL, Ramzy MI, Galal A, Claramonte PJ. Conductive keratoplasty for the correction of residual hyperopia after LASIK. J Refract Surg. 2005;21(6):698–704.
Claramonte PJ, Alió JL, Ramzy MI. Conductive keratoplasty to correct residual hyperopia after cataract surgery. J Cataract Refract Surg. 2006;32(9):1445–1451.
Excerpted from BCSC 2020-2021 series: Section 13 - Refractive Surgery. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.