"Best Doctors
in New York"




"Best Doctors
in New Jersey"

Near Vision Conductive Keratoplasty (CK)

RESEARCH ANNOUNCEMENT: PARTICIPATE IN A CLINICAL TRIAL OF NEAR VISION CK AFTER LASIK. Click here for more information.

The Cornea and Laser Eye Institute - Hersh Vision Group is pleased to be one of the few centers in the United States to offer Near Vision CK , a procedure for improved reading and near vision for people over age 40. In fact, CLEI was one of five centers in the U.S. asked to participate in the original clinical trials of CK.  As part of these studies, Dr. Hersh performed the first CK on the East Coast in May of 1999.  He presented study results at the FDA ophthalmic devices advisory panel in Washington, D.C. in November, 2001, leading to first FDA approval in 2002.  Over the years, CK has proven to be a safe, effective procedure for the treatment of presbyopia (ie the need for reading glasses) and farsightedness, and we have since treated hundreds of patients.

(CLICK HERE for Dr. Hersh's in depth article on CK.)

CK uses radiofrequency (RF) energy, instead of a laser, to reshape the cornea and help patients with near vision and reading. CK may improve reading vision, improve eye fatigue at the end of the day or when reading in poor lighting, common problems of many Baby Boomers are beginning to notice the need for reading glasses as they get older.

Indeed, Baby Boomers (those born between 1946 and 1964) comprise the largest segment of the presbyopic (ie reading glass) population. Presbyopia occurs when the lens inside the eye becomes stiffer, and less able to focus up close, with age. It's the most common vision disorder in America and affects more than 60 million people over age 40. CK is one of the first procedures designed specifically for the millions of people with presbyopia. Symptoms of presbyopia include difficulty reading menus, computer screens, or the need to constantly reposition reading material to find the right focus.  Patients may also have trouble driving at night.

The CK procedure is performed using a small probe, thinner than a strand of human hair, that releases radiofrequency (RF) energy. After application of a topical anesthetic (i.e., eye drops), radiofrequency (RF) energy is applied in a circular pattern to shrink small areas of corneal tissue. This circular shrinkage pattern creates a constrictive band (like the tightening of a belt), increasing the overall curvature of the cornea. The result is somewhat like wearing a bifocal contact lens. The use of RF energy is one of today's most advanced surgical techniques. In addition to its use in CK, RF technology is being used in prostate cancer therapy, back surgery, even cardiovascular procedures.

Candidates for CK must meet the following criteria:

  • Be over 40 years of age
  • Wear reading glasses
  • Not have had previous vision surgery
  • Not have had any significant changes in vision for one year
  • Not have any chronic eye disorders
  • Not be pregnant or nursing
  • Not have any chronic illness or disease
Before CK, of course, a complete examination is necessary.  The CK procedure itself is comfortable.  There may be a dry eye or foreign body sensation for a day or two afterwards. Once finished, you don't have to wear a patch and can usually return to work the next day. Vision begins improving in about a week's time.

Conductive Keratoplasty (CK) for the Treatment of Presbyopia
 
By Peter S. Hersh, M.D.
 
Conductive keratoplasty, better known as CK, has recently been approved by the U.S. FDA for the treatment of presbyopia. Presbyopia is the age dependent loss of accommodative, or focusing, ability of the human crystalline lens resulting in the need for reading glasses. CK currently is the only FDA-approved procedure to treat presbyopia.
 
Unlike LASIK correction of nearsightedness and astigmatism, the correction of presbyopia is problematic, both practically and theoretically. Most clinical efforts have been directed toward optical arrangements which promote simultaneous near and distance acuity. One general approach is referred to as "monovision" or "blended vision" and achieves depth of focus with differential corrections on each eye, correcting one eye toward a near focal point.(1) This approach has been utilized clinically with contact lenses for years.(2) Ocular dominance first is determined by sighting tests; the non-dominant eye generally is selected for near vision treatment. Trial contact lens fitting with analysis of patient response is often used as a final basis for selection of the near point eye and to determine good candidates.
 
Conductive keratoplasty, or Near Vision CK, achieves this optical result surgically. CK utilizes high frequency, low-energy electric current to shrink corneal collagen. Initially developed by Mendez (3), the CK instrument and procedure were developed by Refractec, Inc (Irvine, CA). CK was originally approved in 2002 for the correction of hyperopia of up to +3.25 diopters. The one year results of the prospective, multicenter clinical trial of CK for hyperopia have been previously published.(4) CK was approved this year for the treatment of presbyopia.
 
The CK instrument delivers 350 kHz radiofrequency (RF) energy via a sterile, disposable, 450 micron guarded stainless steel probe which is inserted into a reusable handpiece. During each application, RF energy is delivered for 0.6 seconds at an energy level of 0.6 watts. The inherent electrical impedance of the corneal stroma results in heating of the tissue to approximately 65o C, the optimal temperature for collagen shrinkage.(5)
 
In the CK procedure, the surgeon places a series of circumferential spot applications, contracting corneal collagen like a belt in the midperiphery with resultant central corneal steepening. This causes an increase in the focal power of the eye, bringing near objects into better focus; hence, the need for reading glasses is diminished. The effect of CK is determined the number of spot applications, the number of rings of applications, and the diameter of application rings. Rings of 8 evenly spaced spots can be placed at 6 mm, 7 mm, and 8 mm. In addition, a second ring of 8 spots can be placed a 7 mm. Thus, treatments consist of 8, 16, 24, or 32 spots depending on the degree of correction desired.
 
Surgery is performed with topical anesthesia and takes approximately 10 minutes per eye. A lid speculum holds the lids open. The patient is asked to look at a fixation target and a CK marking instrument coated with gentian violet or methylene blue marks the application spots centered over the pupil. The spots are then applied consecutively. Afterwards, the patient uses artificial tear drops and sometimes an antibiotic and corticosteroid drop for one week. The patient may experience some foreign body sensation afterwards and fluctuation in vision for a few weeks after the procedure.
 
Candidates for CK should have correctable distance visual acuity to at least 20/40 in both eyes, and near visual acuity correctable to at least J3 in the non-dominant eye. They should be 40 years of age or older and require a presbyopic add of +1.00 to +2.00 D. CK results may not be permanent and patients, as they age, may again require reading glasses. CK retreatments may be performed, but results of retreatments have not been rigorously assessed, to date.
 
In an attempt to look at the clinical safety and effectiveness of CK for the treatment of presbyopia, a multicenter clinical trial studied 150 consecutive subjects. As in clinical use today, the treatment plan was designed to correct the non-dominant eye for near vision. (Thus, patients without distance vision problems usually require only one eye to be treated. Those with hyperopia in the other eye may require bilateral treatment.) This study was done as part of a Phase III multicenter clinical trial of the Refractec Viewpoint Conductive Keratoplasty system (Refractec, Inc., Irvine, CA) for the treatment of presbyopia.
 
Twelve month results of the CK presbyopia trial are available on 106 patients (unpublished preliminary data). At one year followup, 80% of patients had achieved newspaper-print size near vision or better. On subjective questionnaires, 97% of patients noted improvement in the quality of their vision and 84% ranked their near vision as being better after the procedure. Eighty-five percent of patients were satisfied, 11% were neutral, and 5% were dissatisfied with the outcome of the procedure. Of dissatisfied patients, 80% still could not see newpaper-size print, suggesting that the foremost criterium for success in the near vision CK procedure is achievement of good uncorrected near visual acuity. In regard to complications and side effects, at 1 year followup, 1 eye (0.9%) lost 2 or more lines of spectacle corrected visual acuity. Eleven percent of patients ranked their distance vision as being worse and approximately 20% noticed some compromise in depth perception, generally in a mild range.

CLICK HERE for Dr. Hersh's definitive in depth article on CK.
 
REFERENCES
1. Jain S, Indu A, Azar D. Success of monovision in presbyopes: review of the literature and potential applications to refractive surgery. Survey of Ophthalmology. 1996;40: 491-498.
2. Hersh D. A novel modality for management of presbyopic contact lens patients. Opt. Journ and Review of Optom. 1969; 106.
3. Mendez A, Mendez Noble A. Conductive keratoplasty for the correction of hyperopia. In: Sher NA, ed. Surgery for Hyperopia and Presbyopia. Baltimore:Williams and Wilkens;1997:163-171.
4. McDonald MB, Hersh PS, Manche EE, Maloney RK, Davidorf J, Sabry M. Conductive keratoplasty for the correction of low to moderate hyperopia: U.S. clinical trial 1-year results on 355 eyes. Ophthalmology 2002;109:1978-1989.
5. Stringer H, Parr J. Shrinkage temperature of eye collagen. Nature 1964:204:1307.