CONDUCTIVE KERATOPLASTY

Although nonsurgical correction (ie, glasses, contact lenses) for patients with low-level hyperopia and presbyopia has been widely successful throughout the world, the surgical correctional procedures have been somewhat less accepted. (See History of the Procedure.) Conductive keratoplasty (CK), an advanced method for vision correction using controlled-release radiofrequency energy to gently reshape the cornea and to provide long-lasting vision correction, is now available for these patients.

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1. History of the procedure

2. Problem

3. Frequency

4. Etiology

5. Pathophysiology

6. Clinical

7. How is NearVision CK performed?

8. Will you be cutting the cornea?

9. Is radiofrequency (RF) energy safe for use on the eye?

10. Will my vision fluctuate after NearVision CK is performed?

11. Are both eyes treated on the same day?

12. Will I have to wear patches over my eyes after the procedure?

13. How soon can I return to work?

14. What type of anesthesia is used during the NearVision CK procedure?

15. What will I feel during the NearVision CK procedure?

16. Why doesn't NearVision CK use a laser?

17. Will the instrument used in the NearVision CK procedure penetrate my cornea?

18. How is a precise amount of RF energy and depth of treatment ensured during the NearVision CK procedure?

19. What are the risks and side effects of NearVision CK?

20. Are there restrictions after having NearVision CK?

21. Am I guaranteed 20/20 vision following NearVision CK?

22. Is NearVision CK reversible?

23. Will my health insurance cover the cost of the NearVision CK procedure?

24. Can CK treat myopia (nearsightedness)?

25. Who is right for NearVision CK?

26. Can NearVision CK be performed on patients who have a pacemaker?

27. What enables NearVision CK to be performed in-office?

28. How do I get more information?

History of the Procedure:

Laser and laserlike surgical procedures for the correction of hyperopia have a checkered history. For this article, the discussion is limited to CK.

The history of CK for hyperopia began with Fyodorov, the inventor of radial keratotomy (RK). He inserted a hot needle at the peripheral cornea to induce shrinkage. This procedure was called hot needle keratoplasty; others referred to it as HNE (hot needle in the eye). Fyodorov encountered problems with consistency and maintenance of the temperature because the temperature went down as the hot needle entered the cornea. A scorching sound was produced each time the needle was applied on the cornea. The procedure resulted in an uneven application of heat, with the external cornea receiving more heat than the inner cornea. Summit laser then introduced its Holmium laser for contact laser thermal keratoplasty, which also failed. Early attempts with hyperopic photorefractive keratectomy (HPRK) were besieged by haze and regression.

The aforementioned procedures were successful in correcting some degree of hyperopia; however, long-term stability, vision quality, and patient comfort were not properly addressed. They were all instrumental as building blocks for the success of hyperopic laser in situ keratomileusis (LASIK), which currently provides excellent outcomes for low levels of hyperopia; low levels of hyperopia are classified as +3.00 diopters (D) in the United States and up to +5.00 D in Canada.

In 1995, Sunrise introduced its noncontact Holmium laser for hyperopic correction via laser thermal keratoplasty (LTK). The problems that beset this particular technology were also related to the regression associated with the unequal distribution of energy from the base to the apex.

Mendez then discovered CK. This revolutionary procedure presents convincing advantages over hyperopic LASIK and hyperopic correction via LTK. CK uses high radiofrequency energy that is delivered with a thin metal tip in concentric rings of multiple spots around the corneal periphery, shrinking collagen and steepening the central cornea. Refractec manufactures and markets this technology.

Problem:

The central problem in the correction of hyperopia and presbyopia is the pressing challenge of steepening the central cornea.

Current treatment modalities include excimer laser ablation of the corneal periphery via either photorefractive keratoplasty (PRK) or LASIK and shrinkage of collagen in a circular pattern in the corneal periphery (eg, LTK). Hyperopic LASIK has been described as widely successful for low levels of hyperopia; however, the risk of flap-related complications cannot be overlooked. Thermal keratoplasty alters corneal curvature by heating the stromal tissue and causing the shrinkage of collagen. An optimal collagen shrinkage profile is currently acceptable. Previous experience has shown that too low of a heat causes minimal effect, while excessive heat causes remodeling and regression of effect. Two methods of collagen shrinkage are available: application of laser energy (ie, LTK) and application of radiofrequency energy (ie, CK).

The Food and Drug Administration (FDA) Phase III clinical trials for CK included the following investigators: Penny A. Asbell, Marguerite McDonald, Robert K. Maloney, Jonathan Davidorf, Peter Hersh, Edward E. Manche, and Daniel Durrie. The study was a prospective multicenter clinical trial to evaluate both the safety and the effectiveness of the ViewPoint CK system for the correction of hyperopia using the CK procedure. The study design was consistent with FDA guidance for refractive surgery lasers (September 1997) and draft American National Standards Institute (ANSI) guidance regarding laser systems for corneal reshaping.

The aim of the study was for a full correction of spherical hyperopia (ie, target of plano). All the treatments were based on preoperative cycloplegic refraction spherical equivalent (CRSE). Eligible patients for the study included those in the range of +0.75 D to +3.25 D of spherical hyperopia, with -0.75 D or less of refractive cylinder, yielding +0.75 D to +3.00 D cycloplegic spherical equivalent.

The effective parameters included improvement in uncorrected visual acuity (UCVA), predictability, stability, and patient satisfaction.

Frequency:

Although numerous figures are reported in publications, the exact number of hyperopes in the world is unknown. Generally, hyperopia is believed to affect millions of persons in the United States and hundreds of millions of individuals around the world.

Of those individuals older than 50 years, 100% of them need corrective lenses for presbyopia.

Etiology:

Errors in refraction may be inherited, and hyperopia may run in families.

Pathophysiology:

In CK, a controlled release of radiofrequency energy is delivered intrastromally via a probe tip (450 mm X 90 mm). Impedance of the corneal tissue results in a thermal effect. Thermal profile is homogeneous to approximately 80% of the depth of the cornea. The CK footprint has an average width of 405 mm and an average depth of 509 mm, as measured with ultrasonic biomicroscopy.

Clinical:

At some point, most, if not all, patients with hyperopia complain of a reduction in vision. The degree of blur depends on the amount of refractive error present. Both near vision and distance vision may be affected. Age may affect the reduction in visual performance. Patients with mild hyperopia, who function well prior to the presbyopic years, begin to experience difficulty with near work once their age approaches 40 years. Visual improvement is excellent with appropriate correction.

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How is NearVision CK performed?

NearVision CK uses radio waves, instead of a laser or scalpel, to reshape the cornea and bring near vision back into focus. NearVision CK is performed using a small probe, thinner than a strand of human hair, that releases radio waves. The probe is applied in a circular pattern on the outer cornea to shrink small areas of collagen. This circular shrinkage pattern creates a constrictive band (like the tightening of a belt), increasing the overall curvature of the cornea. The procedure, which takes less than three minutes, is done in-office with only topical anesthesia (eye drops).

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Will you be cutting the cornea?

NearVision CK is performed without the cutting or removal of tissue. It is a safe, minimally invasive procedure for Baby Boomers who struggle to read a newspaper, menu, alarm clock, computer, etc.

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Is radiofrequency (RF) energy safe for use on the eye?

Yes. The use of RF energy is one of today’s most advanced surgical techniques. In addition to its use in NearVision CK, RF technology is being used in prostate cancer therapy, back surgery, orthopedics, cosmetics, and even cardiovascular procedures. Will my vision improve immediately after the NearVision CK procedure? Patients usually notice an immediate improvement in their vision after the NearVision CK procedure. However, it usually takes several weeks for the eyes to reach the final level of treatment.

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Will my vision fluctuate after NearVision CK is performed?

Most patients will experience mild fluctuation in their vision after the procedure, but few notice it. Any fluctuation will usually subside within a few weeks. Patients who have a procedure to steepen the cornea (presbyopia or hyperopia), regardless of the procedure, usually require a longer stabilization period than those who receive a treatment that flattens the cornea (myopia.)

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Are both eyes treated on the same day?

NearVision CK is typically performed on just one eye. However, if a patient’s prescription requires treatment in both eyes, CK is typically performed on both eyes on the same day—one eye immediately after the other. Most patients are comfortable having the CK procedure performed on both eyes on the same day because the procedure is minimally invasive, takes less than three minutes, and is done in-office with only topical anesthesia

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Will I have to wear patches over my eyes after the procedure?

You will not have to wear patches or bandages.

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How soon can I return to work?

With NearVision CK, the majority of patients are able to return to work and other normal activities the day after their procedure. Although recovery is fairly quick, it is advisable to be careful with your eyes and to avoid any strain. Those whose jobs demand intense clarity of vision (such as dentistry, surgery or computer work) may want to give their eyes some extra rest for a day or two following the procedure before going back to work.

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What type of anesthesia is used during the NearVision CK procedure?

A topical anesthetic in the form of eye drops is used to numb the eye. Those patients who are nervous or have a high level of anxiety will be given a mild sedative to help them relax.

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What will I feel during the NearVision CK procedure?

The CK procedure is considered painless. You will be aware of a lid support (speculum) which helps to hold your eye open. The most common sensation that patients experience is a slight feeling of pressure on the eye. After surgery, there may be some mild discomfort, which is often managed with drops and/or analgesics. Many patients complain of a foreign-object sensation or a slight "scratchiness" in the eye. This usually subsides within 24 hours of the procedure.

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Why doesn't NearVision CK use a laser?

NearVision CK is a non-laser procedure that uses controlled radio waves to improve near vision. Rather than removing tissue with a laser, NearVision CK reshapes the cornea using an entirely different method: the application of low-level radiofrequency (RF) energy applied in a circular pattern on the outer cornea to shrink small areas of collagen in the corneal tissue. This circular pattern acts like a belt tightening around the outer cornea to increase its overall curvature and bring life’s details back into focus. The procedure, which takes less than three minutes, is done in-office with only topical “eye-drop” anesthesia.

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Will the instrument used in the NearVision CK procedure penetrate my cornea?

NearVision CK is performed using a small pen-like instrument (Keratoplast™ Tip) that is as thin as a strand of human hair. The tiny probe, introduced in tiny spots around the outer edges of the cornea, applies controlled radiofrequency (RF) energy, stabilizes the CK procedure and guarantees the precise depth of treatment.

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How is a precise amount of RF energy and depth of treatment ensured during the NearVision CK procedure?

The technology used during the procedure was engineered and designed specifically for performing NearVision CK. This means that the precise amount of RF energy needed to affect the corneal tissue, at the precise tissue temperature and depth of treatment, were meticulously investigated and defined. The Keratoplast Tip penetrates the cornea to a depth of 450 microns and utilizes a plastic stop at the very tip to assure precise depth of treatment.

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What are the risks and side effects of NearVision CK?

Because NearVision CK is minimally invasive and very controlled, the procedure has exhibited very minimal risk and almost no side effects. During the first 24 to 48 hours after CK, you may experience tearing and some discomfort, including a foreign-object sensation in the eyes. You may also experience a slight over-correction of your vision, allowing you to see better up close, though your distance vision may appear slightly blurry at first. This will stabilize during the following weeks.

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Are there restrictions after having NearVision CK?

As with any vision treatment procedure where the cornea is altered, certain precautions should be taken. After the NearVision CK procedure, patients should avoid getting contaminated water in their eyes for at least one week. This includes water from swimming pools, spas, lakes and the ocean. When showering or taking baths, you should keep your eyes closed in order to avoid getting soap and dirty water in them. When exercising, sweat should be kept out of the eyes for at least a week after surgery. Also, you should avoid rubbing your eyes vigorously for two weeks following the procedure. Females should avoid eye makeup for several days after the procedure.

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Am I guaranteed 20/20 vision following NearVision CK?

No. And no honest eye surgeon can absolutely guarantee a certain result from any vision treatment procedure. However, in the FDA clinical study, nearly 87% of patients had 20/20 vision while looking at objects in the distance, while being able to read phonebook-size print (J3) after having NearVision CK (12 month follow-up data.)

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Is NearVision CK reversible?

As with most vision treatment procedures, NearVision CK is not reversible. Once the procedure has been performed, it is not possible to "remove" its effects. This is an important factor for anyone thinking about undergoing a vision correction procedure to carefully consider. To make sure CK is right for you, seek the advice of your doctor.

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Will my health insurance cover the cost of the NearVision CK procedure?

Because NearVision CK is considered elective (cosmetic) surgery, most health insurance plans do not cover it.

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Can CK treat myopia (nearsightedness)?

NearVision CK was designed for Baby Boomers who struggle to read menus, price tags, or see their computers—symptoms of fading near vision which require steepening of the cornea. NearVision CK is not designed to flatten the cornea, the effect required for the treatment of myopia, or nearsightedness.

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Who is right for NearVision CK?

You’re likely a good candidate for NearVision CK if you:

1. Are at least 45 years of age

2. Have great distance vision without glasses or contact lenses.

3. Dislike wearing reading glasses

To determine if NearVision CK is right for you, visit your eye care practitioner to discuss the complete list of indications and contraindications.

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Can NearVision CK be performed on patients who have a pacemaker?

The NearVision CK equipment can produce interference that may adversely influence the operation of other electronic equipment. Therefore, NearVision CK is contraindicated for patients who are wearing a pacemaker.

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What enables NearVision CK to be performed in-office?

NearVision CK is a minimally invasive procedure that does not require cutting of the cornea, and therefore does not carry the associated risks or surgical complications. The procedure is relatively quick and easy to perform—taking an average of just 3-5 minutes.

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