Stability of Refraction During Four Years After Radial Keratotomy in the Prospective Evaluation of Radial Keratotomy Study: Reply

Stability of Refraction During Four Years After Radial Keratotomy in the Prospective Evaluation of Radial Keratotomy Study: Reply

Vol. 113, No. 1 are possible. One may tilt the forceps back, still retracting the iris, to permit the nucleus to ride over the closed blades with the...

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Vol. 113, No. 1

are possible. One may tilt the forceps back, still retracting the iris, to permit the nucleus to ride over the closed blades with the iris underneath, then slide the forceps from under the nucleus, and use it to nudge the nucleus out of the eye. This technique works best with large nuclei. Alternatively, the forceps are tilted back and the jaws opened to receive the dislocating nu­ cleus, as it rides over the lower blade, which retracts the iris. Small nuclei may be delivered by this method. When the instrument is used in this manner, it is generally not necessary to exert any pressure on the eye near the incision to dislocate the nucleus, thereby protecting the integrity of the zonules in the area. The forceps shown in Figure 1 are for the right hand. For­ ceps for the left hand are a mirror image of this instrument.

"The forceps were made by Karl Ilg Industries, Inc., St. Charles, Illinois.

Correspondence Correspondence concerning recent articles or other mate­ rial published in THE JOURNAL should be submitted within six weeks of publication. Correspondence must be typed double-spaced, on 8V2 x 11-inch bond paper with IVi-inch margins on all four sides and should be no more than two typewritten pages in length. Every effort will be made to resolve controversies between the correspondents and the authors of the article before publication.

Stability of Refraction During Four Years After Radial Keratotomy in the Prospective Evaluation of Radial Keratotomy Study EDITOR:

The article, "Stability of refraction during four years after radial keratotomy in the Pro­ spective Evaluation of Radial Keratotomy Study," by G. O. Waring III and associates (Am. J. Ophthalmol. 111:33, February 1991), was of great interest. The study design, meth­ ods, and data-gathering techniques were su­ perb and serve as an example of the authors' profound commitment to a comprehensive un­ derstanding of radial keratotomy. I commend them for their diligence.

Correspondence

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The data raised several points of potential concern that can be analyzed under worst and best case situations. Consider the worst case first. From six months to four years, the percent­ age of patients who have 1.0 diopter or greater hyperopic shift increased from 5.3% to 22.6%. There were no data to indicate that this trend was decreasing or self-limited. In other words, if the trend continues, 100% of patients would eventually have 1.0 diopter or more of hyper­ opic shift. For many patients, particularly those slightly undercorrected, this would be a welcome change, whereas others would be­ come overcorrected. The authors note that the average hyperopic shift over four years for the entire population studied was 0.4 diopter. Thus, roughly, there is 0.1 diopter of hyperopic shift per year. If this rate is constant, there would be approxi­ mately 1.0 diopter of hyperopic shift per dec­ ade. After 40 years, the average patient would have 4.0 diopters of hyperopic shift. Such a shift would be unwelcomed by most patients. The authors noted that patients with smaller optical zone sizes tended to have more hyper­ opic shift, which implies that some patients may be more profoundly affected than others. The best case would be that in which the patient's refraction stabilized or that we could somehow control this shift to the patient's ad­ vantage (with patching or pharmacologic agents). Such an outcome would be reassuring to patients and physicians alike. The most likely outcome for refractive errors in these patients probably lies somewhere be­ tween the worst and best case. However, we cannot predict the outcome without further de­ tailed studies such as the one the Prospective Evaluation of Radial Keratotomy Study has provided. A study of longer duration is obvi­ ously needed so we can rationally advise our patients regarding the long-term safety and ef­ ficacy of radial keratotomy. I urge the study group to continue their work in this important area. SCOTT MACRAE, M.D.

Portland, Oregon

Reply EDITOR:

We thank Dr. MacRae for his observations and agree with him that a detailed study of the

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January, 1992

AMERICAN JOURNAL OF OPHTHALMOLOGY

long-term efficacy and safety of radial keratotomy is needed. The PERK Study has been awarded funding by the National Eye Institute to obtain a clinical examination of patients in the study at approximately ten years after sur­ gery. During 1991 and 1992 the Coordinating Centers will be engaged in tracking the loca­ tion of study patients. The Clinical Centers will begin contacting patients in 1992 and pre­ paring for patient examinations, which will be done during 1993. Data analysis and manu­ script preparation will be done at the Coordi­ nating Centers during 1994 and 1995 along with preparation for possible further follow-up of patients. This study will provide informa­ tion on the intermediate to long-term stability of refractive error after radial keratotomy. GEORGE O. WARING III, M.D. AND THE PROSPECTIVE EVALUATION OF RADIAL KERATOTOMY STUDY GROUP

Anterior Chamber Aspirate Cultures After Uncomplicated Cataract Surgery EDITOR: The article, "Anterior chamber aspirate cul­ tures after uncomplicated cataract surgery," by J. B. Dickey, K. D. Thompson, and W. M. Jay (Am. J. Ophthalmol. 112:278, September 1991), contains a flaw in methodology, which may account for the large percentage of pa­ tients with culture-positive anterior chamber aspirates. Antiseptic preparation consisted of hexachlorophene, followed by saline rinse, and finally povidone-iodine. This combination of cationic and. anionic soaps creates neutraliza­ tion of both preparation solutions, thereby ne­ gating their bacteriostatic and bacteriocidal ef­ fects. It would be interesting for the authors to repeat their study, substituting either of the preoperative facial preparation agents individ­ ually to learn if the anterior chamber colony counts would drop further. ROBERT T. MCBRATNEY, D.O. Tulsa, Oklahoma Reply EDITOR: Dr. McBratney is correct in his statement that the combination of cationic and anionic

soaps creates neutralization of both deter­ gents, thereby negating their antimicrobial properties. A well-known example of this prin­ ciple occurs when the quaternary ammonium compound, benzalkonium chloride (a cationic antiseptic), is neutralized on exposure to the anionic detergent hexachlorophene. 12 Howev­ er, both the iodine in the 5% povidone-iodine and the chloride in the 0.25% hexachloro­ phene used in our study were anionic in na­ ture, 3 and in the form of solutions without soap. These anionic antiseptic solutions, povi­ done-iodine and hexachlorophene, are there­ fore supplied in an acidic medium, and their antibacterial activity would be expected to be reduced on exposure to cations in the alkali 1 (but not on exposure to other anions). The problem of ionic neutralization, therefore, does not exist between povidone-iodine and hexachlorophene, since they are both anions. JAMES B. DICKEY, M.D. KENNETH D. THOMPSON, Ph.D. WALTER M. JAY, M.D. Maywood, Illinois

References 1. Reynolds, E. F., Parfitt, K., Parsons, A. V., and Sweetman, S. C. (eds.): Martindale, The Extra Phar­ macopoeia, ed. 29. London, The Pharmaceutical Press, 1989, pp. 949, 952, 963, and 1187. 2. McEvoy, G. K., and Litvak, K. (eds.): AHFS Drug Information, ed. 33. Bethesda, American Socie­ ty of Hospital Pharmacists, Inc., 1991, pp. 21212123. 3. Siebring, B. R., and Schaff, M. E.: General Chemistry, ed. 1. Belmont, California, Wadsworth Inc., 1980, p. 145.

Isolated Neurofibromas of the Conjunctiva EDITOR: In the article, "Isolated neurofibromas of the conjunctiva," by P. H. Kalina, G. B. Hartley, G. Campbell, and H. Buettner (Am. J. Ophthal­ mol. 111:694, June 1991), Table 2 summarizes the published reports of isolated neurofibroma of the conjunctiva. The authors were making a case for the finding of systemic neurofibromatosis in the majority of patients who have iso-