Q: One current method of reoperating on radial keratotomy patients who had an optical zone greater than 3.00 mm is to open the previously made wounds with a blunt instrument, remeasure the corneal depth, and, using a front cutting blade, reçut these incisions to a smaller optical zone.
1) Do you use this method or a modification of this method? How have you modified it?
2) Do you open the previous incisions their entire length, or, if not, how many of the incisions do you open?
3) How much additional correction do you anticipate assuming that the original cuts were adequate?
4) Do your anticipated results differ on a reoperation on a four cut versus an eight cut radial keratotomy?
When I first read Dr Frank's article on the technique of "backcutting" I was interested in the corrections he was obtaining, but immediately I thought about the problems I have seen in the past with reopening or recutting previously made keratotomy incisions. I did subsequently have a patient who came in and had heard about this technique, and after explaining the potential problems with wound healing and possible increased glare, and following the patient's consenting to proceed in spite of these warnings, I performed the technique for the first time.
The patient initially had a 4.0 mm optic zone with eight incisions and undercorrected by 1.5 D. I followed Frank's suggestions and used a 3.0 mm optic zone and made a second 5.0 mm optic zone mark and cut from the 5 to the 3 in a reverse cutting or Russian style technique. This gave me an additional correction of 1.62 D at 6 months. The patient did not experience any greater glare than in the other eye which had initially undergone an eight incision radial keratotomy with a 3 mm optic zone, but without reoperation.
The technique I utilize is to reçut within the same incision with a front cutting blade. In order to insure that you are in the same incision it is essential that the knife be placed under high magnification. Another trick is to open the wound slightly with a blunt instrument and then to plunge the knife into its full depth and cut centrally. There is increased scarring when performing this technique but I have been impressed that the patients do not complain of increased glare, although I have not checked them with a glare tester.
I would caution the surgeon to be prepared to meet an obstruction while cutting when the knife reaches the end of the previously made radial incision. This obstruction produces resistance to the knife; care must be taken when advancing it at this point since it may "run" into the visual axis. I set the knife at 100% of the central pachymetry; any deeper than this produces microperforations.
When looking at my results of backcutting on four and eight incisions, I found a mean correction of only 0.37 D with four incisions and 0.95 D with eight incisions. This is a mean and obviously there are cases that received no effect. The greatest effect I achieved wa 2 D. The cases that had an initial 3.0 mm optic zone with adequate depth by slit-lamp examination received little or no effect as would be anticipated.
My overall impression of the technique is that it does work and is ideally suited for patients with optic zones of 3.5 or greater performed at the initial surgery. The backcutting should be done to a 3.0 mm optic zone and all eight incisions should be reçut. With this, one would expect approximately 1 diopter of additional correction. The knife should be set at 100% of central pachymetry and care should be taken when reaching the end of the initially made radial incision since obstruction is encoutered at this point and the knife is likely to run. Stabilization is rapid and increased scarring is noted which does not appear to bother the patient.
RICHARD A. VILLASENOR, MD
Mission Hills, California
This is a method I used 8 or 9 years ago only when it was obvious early in the postoperative period that the refractive error was grossly undercorrected. If a -6.00 myope was -4.00 after approximately 2 weeks and the incisions appeared shallow on slitlamp examination reopening the incisions throughout their entire length by blunt dissection, redeepening those incisions to an adequate depth, and perhaps even extending the incisions to a smaller optic zone often proved to be successful. It is my experience that significant additional correction is not likely if the original cuts were made at an adequate depth. This maneuver could even result in a loss of effect.
In addition, opening and redeepening of old incisions can result in broader and denser scarring and perhaps inclusion of epithelial plugs into the incisions, increased glare, and perhaps prolong corneal instability and fluctuation of vision.
I believe there would be greater chance for success and greater safety for the patient to add new incisions. The depth of these incisions and the use of a smaller optic zone would be determined by the patient's residual refractive error and the appropriate corneal measurements. Depending on the original and residual refractive error and number of incisions in the initial procedure an additional four or eight incisions could be made. In experienced hands an additional 50% to 60% effect can often be achieved by adding four additional incisions to an original four cut RK. However, eight additional incisions to an original eight cut RK often achieves only 10% to 20% additional effect.
In summary, in reoperating on radial keratotomy patients I would suggest adding an additional four to eight new incisions which could include, if warranted, slightly increased depth and length of incisions. If the patient already has 16 incisions and the surgeon is convinced that additional surgery could be beneficial, my suggestion would be to redeepen eight equi-distant incisions that are the shallowest as determined by slit-lamp biomicroscopy with a back cutting blade from limbus toward optic zone through the original incision site and carry these incisions to a smaller optic zone.
I believe that the addition of new incisions into "virgin" cornea gives the surgeon more control and more consistent results, and greater safety to the patient.
ROBERT H. MARMER, MD
Typically, my reoperations are blocked into two categories: those in which incisions are redeepened, and those in which incisions are added. Typically, the redeepening of incisions is done with a closed incision. It was true that in the past we had opened incisions, but we've found that the results are far more satisfactory if we leave the incisions closed, for a number of reasons, not the least of which is the bottom of the incision is not flayed, and also the straightness of the incision is improved, or the tracking, if you will. We redeepen incisions that are grossly under-depth within the first month, if possible. If much more time than 30 to 40 days have elapsed, we wait until six months before we will attempt to redeepen incisions. We have found in our experience that attempts to modify surgical incisions between 1 month and 6 months postop has inevitably led to less than desired results, or in some rare instances an actual loss of the previous effect.
We do not open the previous incisions at all. We have abandoned the method of free-hand deepening to Descemet's membrane and prefer to use a vertical edge cutting blade, and fixating either limbus to limbus tangentially perpendicular to the line of incision, or preferably behind the knife so that complete control is obtained. Using a vertical cutting blade and a sewing machine type foot on our knife, which happens to be the Katena XTAL handle and blade, we are able to track along the previously made incision without too much difficulty. Typically when we do these incisions we do so in a stepwise fashion, cutting from the limbus to 8 mm and then adjusting the blade to compensate for the change in corneal thickness and cutting from 8 to 6, then readjusting the blade and cutting from 6 on in to whatever the optical zone has to be. In some instances we have extended the incision in this way. We have found, in our hands at least, that this is the best method. In the event that we add incisions, we then add those incisions as appropriate, usually after six months but in rare instances before the first 30 days have elapsed.
In the instance of adding incisions, we typically get something around 80% of an anticipated correction in this respect. For example, let's assume that we do a 6incision case and there is some residual. Were we to add that to the original correction and calculate for this, we find that by adding the additional six incisions we would get something like 80% of what would be predicted for 12 incisions with that original amount of correction. There have been some variations in this, and unfortunately it is not entirely predictable, and in these instances it may be necessary to be guided by one's experience.
We do find anticipated results differ considerably in reoperations on a 4-cut versus 8-cut. We do not typically stage our surgery as advocated by some. For example, we don't feel that a patient who requires 8 cuts has any benefit from doing a 4 plus 4. We have found that the amount of surgery obtained without modifying the optical zone materially, in doing 4 and then adding 4, the effect is not the same as if we had done the 8 at one sitting. We can appreciate that the thrust of advocating the staged 4 is to prevent overcorrections. Our overcorrection rate is sufficiently low and the satisfaction rate sufficiently high doing it our way, that we don't intend nor do we advocate staging incisions.
LEO D. BORES, MD
Currently I do use a recutting method for undercorrected radial keratotomy patients. I open the incisions with a Sinskey hook and scrape out the epithelial facet. I mark the appropriate optical zone, usually a 3 mm zone centrally. I then also place a mark at 7 mm. We have found that cutting from 7 to 3 is all that is required. Cuts outside a 7 mm zone appear to have almost no effect and cuts in the far periphery of the cornea actually appear to steepen the cornea.
I tend to open the incisions between the central limit and the periphery but I only reçut from 7 to 3 or occasionally to 2.8.
I set the blade at 100% of paracentral pachymetry and use a Russian style, front cutting or knife which you push. I then push this centripetally from the 7 mm optical zone to my selected central zone.
If the original cuts were adequate we have found that we can achieve an additional 1 D or so. If the initial cuts were inadequate then one needs to calculate the usual efficacy of a 4 or 8 incision radial keratotomy at that optical zone and add one half to 1 D. Recutting all eight incisions verses a four incision reçut operation is likely to achieve a slightly greater effect, approximately 30% more.
To date the data are still very preliminary in this area but we have found this to be a useful technique and it does not require additional incisions. I currently never use 16 incisions in any cornea but prefer the deepest possible 4 incision or if necessary eight incision procedure.
RICHARD L. LINDSTROM, MD