Off-label Conductive Keratoplasty

Off-label CK can provide an easy, minimally invasive solution to improve reading vision.

BY DANIEL S. DURRIE, M.D.

Off-label use for conductive keratoplasty (CK) includes post–refractive surgery patients, such as previous LASIK and PRK patients, as well as post-cataract patients. Essentially, the off-label use is an extension of the on-label use in the same patients, the plano presbyopes, although they have had previous surgery.

Approved CK

The clinical research for CK was conducted more than 8 years ago. CK has been approved since 2002 for the temporary reduction of hyperopia. In April 2004, CK received an additional FDA indication for presbyopia and improving near vision in the presbyopic patients. I have found CK's major on-label benefit has been in the latter group and I no longer use it for hyperopia greater than 1.00 D.

I believe, as many surgeons do, that CK is an excellent procedure for patients who have a very mild amount of hyperopia and presbyopia (Figure 1). The ideal patient is usually -0.50 D of myopia to +0.75 D of hyperopia. They are aged 48 to 60 and have great distance vision but do no like using their reading glasses. CK has proved very effective for this group. Some doctors use CK for astigmatism and hyperopia. In my opinion, on occasion, it can be used. However, there often are better modalities to treat these patients.

Over the years, my use of CK has been limited to on-label use for those patients who are plano presbyopes, and who do not have a cataract or enough nuclear sclerosis to take the lens out and implant a premium IOL. Many patients prefer CK to monovision LASIK because it is "non-cutting" and simple to perform. In addition, we can titrate to effect, "a little CK can be done now and little bit later" as the patient becomes more presbyopic.

Figure 1. CK is approved for the temporarily reduction hyperopia and for improving near vision in presbyopic patients. CK is an excellent procedure for patients who have a very mild amount of hyperopia and presbyopia.

Also, I have found that some patients are wary of surgery because they have had perfect vision all their lives and they are not accustomed to the idea of having vision correction. Thus, surgeons can place just 8 CK spots with a large optical zone — which is usually 8 mm (Figure 2). This way, patients can be introduced to CK and have more treatment to refine their reading vision later as they want to. This "titration" is difficult to achieve with lasers, and I routinely use this application in my practice.

Figure 2. CK Retroillumination: For on-label CK, patients receive 8 spots at a 7-mm optical zone.

Off-label CK

As I said above, off-label CK is performed on both post-refractive and post-cataract surgery patients Here are my guidelines for each group.

■ Post-refractive Surgery. I have found that there are two main off-label CK uses that are very valuable in my practice. One of them is CK in the exact same patient as mentioned above, but in those patients who have also had LASIK or PRK surgery previously. Within 10 years, many of these LASIK or PRK surgery patients return to the office and note that they are pleased with their distance vision but are having problems with reading. They want a procedure to enhance their reading vision at this stage of their lives.

In more than 5 years of doing CK after LASIK or PRK, we have found that these patients not only fare well, but they seem to do even better than the primary patients. These previous refractive patients do not want their flap lifted and an enhancement performed. Instead, they would rather switch to a procedure that is safer and has no cutting. These are the same reasons people who like CK in the first place. In my experience, the post-LASIK and PRK patients are very satisfied with CK.

We demonstrated in a multicenter prospective study on 150 post-LASIK emmetropic presbyopic eyes receiving an 8-spot CK at an 8-mm optical zone that more than 95% read at J3 or better at 1 month and 3 months (Figure 3).¹

Post-LASIK patients do experience slightly more effect than the patients who have primary CK. Therefore, I usually recommend to surgeons that if they would normally do 8 spots at 7 mm, they should widen the optical zone to 7.5 mm and they will get about the same effect as they would at 7 mm.

The nice thing about this method is that it really is a little less surgery and there is less chance of astigmatism induction.

This is an exciting application because there are millions of post-LASIK, post PRK patients who are getting older every year. In general, this group (who like their distance vision and who are happy with their surgery) is a market that is growing steadily. For example, the significant growth of LASIK and PRK surgery occurred from 1995 to 2001, when it was growing 100% per year. Many patients had surgery during this time period. The average age of those patients was 38. Now, 5 to 10 years later, they are entering the presbyopic age group. Thus, many more ophthalmic surgeons are interested in this off-label use of CK for people who have had previous PRK and LASIK.

Refractec, Inc. (Irvine, Calif.) has conducted a clinical trial for this CK application and it will be applying for FDA approval for this as an indication. However, surgeons can perform this CK indication off-label because we already know that it works. Just remember that, if a patient has had previous PRK or LASIK surgery, they are going to get more effect than a virgin eye. Thus, surgeons should be conservative on the amount that is done initially. I always emphasize that it is easy to come back and do more surgery (spots), but it is hard to take them away. This off-label group of patients is very conservative. Surgeons need to be very careful with this type of patient because they don't want to over treat.

Post-cataract Patient

The other prime off-label CK use is in the post cataract patient who is also a plano presbyope.

CK can be performed on a post-cataract patient who has not had a premium IOL. This group of patients may have friends who have had a premium IOL and have heard of their improved reading vision or they may be interested in improved reading vision in general. Patients tell me they like the idea of a non-LASIK, no-cutting procedure in which they can receive a few CK spots that will most likely result in improved reading vision.

Other Off-label Uses

Another valuable off-label CK application is for post-cataract and refractive surgery (LASIK and PRK) patients who have not achieved desired outcomes. In this application, some previous surgery patients — myopic laser surgery, either PRK or LASIK — or cataract IOL patients, have visual outcomes that have missed the target and they are slightly hyperopic. This group includes patients who have up to 1.5 D of hyperopia. Therefore, the goal would be to make them plano. It is easy to use CK in these cases to get a patient closer to the target.

For example, consider a patient who received a myopic PRK for 8D of nearsightedness that resulted in 1.00 D of hyperopia postoperatively. The surgeon has the option of taking the epithelium off again and doing another PRK (which requires the patient to experience more pain and repeat the healing cycle again) or the surgeon can select CK, which is simple to perform, inexpensive and provides vision the next day without the PRK healing issues.

Figure 3. One-month and 3-month near UVCA for patients who received CK over LASIK.

Another example is the postoperative implant patient. For instance, the doctor placed an implant hoping for plano and resulted with the patient being a +1.00 D. Rather than performing an IOL exchange or performing a LASIK or PRK procedure, the physician can do CK on those patients also. I get referrals to use this application on patients. In these cases, I know I can help. I tell the patients that it is not going to hurt very much, it is not going to cost very much and vision comes back quickly.

Overall, CK has similar on-label and off-label uses. This procedure is a valuable tool to treat a variety of my patients. OM

Reference

1. Stahl ED, Durrie DS, Stahl JE, et al. Results of conductive keratoplasty to improve near vision in presbyopic emmetropes who underwent previous LASIK. Paper presented at: The 110th Annual American Academy of Ophthalmology Meeting; November 13, 2006; Las Vegas.

Daniel S. Durrie, M.D., is medical director of Durrie Vision in Overland Park, Kans. He is also Clinical Professor, Ophthalmology, University of Kansas Medical Center, Kansas City, Kan. He can be reached at ddurrie@durrievision.com or (913) 491-3330.