I find the comments by Nordan and Maxwell1 most disturbing. I do not take exception with the authors' alerting the public to the dangers of using optical zones of 2.50 mm or less for radial keratotomy. However, I feel that the wording of their admonition seems to imply that all optical zones greater than 2.50 mm (ie, 2.75 mm) are safe. This is an assumption that most practitioners find questionable. The conventional wisdom is that the minimum optical zone in radial keratotomy should be 3.00 mm. Where is the evidence that optical zones greater than 2.50 mm and less than 3.00 mm are safe?
Nor do I take exception with the authors' exhortation against ophthalmologists who perform surgery knowing that the particular procedure "has a large chance of permanently reducing" vision by one to two lines. I do question their specific warning concerning hexagonal keratotomy for the correction of hyperopia. (I assume that they are referring to my modification of the original procedure, which I named the Hex-T. In the original operation as described by Méndez, all hexagonal incisions were connected. This is certainly not acceptable. In the Hex-T, a gap is left at the apex of each hexagonal cut. (These spaces are bridged by six transverse incisions.) They alert "the public and our colleagues to the dangers and complications" of a procedure which, to my knowledge, has had no published studies of its effectiveness, stability, or complications. Despite the lack of any documentation in the literature, the authors refer to "irregular corneal astigmatism and significant decrease in the quality of best corrected vision" and offer no more proof of these complications than do the physicians who are verbally extolling its virtues.
This boils down to what I call an argument of emptiness. There is no substance, only rhetoric on both sides. Instead of such empty bombast, I propose prospective studies of patient response to the Hex-T. We are conducting such a series at Tulane Medical Center. I can say without hesitation that none of our initial cases has experienced permanent irregular astigmatism nor suffered decreased best spectacle corrected visual acuity. Clearly, we can draw no conclusions until adequate data have been assembled and evaluated. To accomplish these ends, I invite other serious investigators to undertake their own studies of hexagonal keratotomy. What we need is less verbiage and more facts.
MILES FRIEDLANDER, MD
New Orleans, La
I read with interest Nordan and Maxwell's1 letter regarding hexagonal and radial keratotomy procedures. In general, I agree that any corneal surgical procedure holds the potential for yielding both irregular astigmatism and problems with glare and loss of best spectacle corrected vision. Fortunately, clinically significant problems in this regard with most forms of refractive corneal surgery are infrequent. Those few surgeons who perform significant numbers of hexagonal keratotomies would agree that the procedure is technically more difficult than radial keratotomy and may require more than one surgical event to accomplish a desired result. In my personal experience of roughly 20 hexagonal procedures, none of the patients have had significant problems or complications. Most of the patients have an acceptable refractive result and would recommend the procedure to others.
Glare and poor vision under low light conditions are, I think, problems for all large radial keratotomy corrections; however, it appears that most patients are able to adjust to these difficulties and are not significantly hampered, long term, by these side effects. This, however, is not universally true, and there are certainly occasional patients who are bothered by this problem. These patients, however, are not restricted to those with extremely small optical zones (down to 2.25 mm) and can be seen in patients with 3 mm or larger optical zones. Similar phenomena have been seen with other corneal refractive procedures: keratomileusis, keratophakia, and epikeratoplasty. Therefore, informed consent must deal with this phenomena, but it seems unreasonable to discount these small optical zone procedures entirely.
The loss of one or two lines of best spectacle corrected vision may not be clinically significant. A patient who is best corrected to 20/15, who is now 20/25 uncorrected, is for the most part extremely happy. The patient must be told that their uncorrected vision may not be quite as sharp as their best spectacle corrected vision had been preoperatively. But we see patients who refuse to wear spectacles and who drive an automobile with 20/200 or worse vision. One can hardly say that for such individuals we would be doing a disservice, correcting their vision to 20/25.
THEODORE WERBLIN, MD, PhD
Associate Clinical Professor of
University of Virginia
1. Nordan LT, Maxwell WA. Avoid both keratotomy with small optical zones and hexagonal keratotomy. Refract Corneal Surg. 1992;8:331.