MATERIALS AND METHODS
The study covers 466 consecutive radial keratotomies performed between January 1986 and October 1989. All the procedures were performed by the same surgeon (S.L.L.J.). Ultrasonic pachometry (with a D.G.H. 1000 pachometer, DGH Technology, Ine, Frazer, Pa) was carried out immediately prior to surgery. Twelve measurements were usually taken to localize the thinnest zone. The diamond blade (MEYCO) was set at 100% of the lowest pachometry reading. A single-edged diamond blade was used for the first 20 procedures, and a double-edged blade for the rest.
The center mark was determined with the aid of a glass-fiber device (Keratolux ZEISS, Carl Zeiss, Ine, Thornwood, NY).1'2 A topical anesthetic (Novesine) as well as systemic tranquilizers were used. We adhered to the Hofmann Guide as modified from Thornton and Fyodorov,3 but only four or eight centrifugal incisions, performed from the optical zone to the limbus, were used.
In high myopia, centripetal incisions were used.4 To increase the effect of these incisions, the Krumeich radial keratotomy bridge was utilized in 16 cases. Of the 466 radial keratotomy procedures, centrifugal cuts were performed in 369 eyes (79.8%), and centripetal cuts in 97 eyes (20.8%). Eight eyes were undercorrected; they were retreated with the back-cutting technique described by Franks.5
In cases with astigmatism, the Thornton guide was applied.6 At the end of each procedure, the incisions were irrigated with BSS and gentamicin, and the eye was patched. Topical dexamethasone and neomycin (Chibrocadron) were applied for 1 month postoperatively. In eyes with a perforation, systemic antibiotics were added for 1 week. Eyes with marked postoperative inflammation were treated with subconjunctival steroids and gentamicin. Patients were examined at 1 day, 3 days, 1 week, 2 weeks, 1 month, and 3 months postoperatively.
Eighteen microperforations (3.8%) without loss of the anterior chamber were observed. In no case did the procedure have to be abandoned. Six of these microperforations were seen in the 369 radial keratotomies performed with the centrifugal cuts (1.62%), and 12 were seen in the 97 procedures using centripetal cuts (13.3%). Six of these occurred during the eight reoperations - two microperforations in each eye in the first three treatments. Two-thirds of the microperforations were noted in the centripetal procedure, and these results correspond with reports that complications occur ten times more often with this technique.7,8
FIGURE: Macroperforation with two sutures in an eye in which a centripetal procedure was done.
None of these patients developed any postoperative complications.
Seven cases of macroperforations (1.5%) were seen. In one case, the procedure had to be abandoned. Two sutures were placed in three of these cases (Figure), and one suture was used in each of the remaining four. Six of the macroperforations were observed in the 97 centripetal incisions (6.6%), and one was observed in a centrifugal procedure (0.2%).
No postoperative complications were seen.
Incisions Into Clear Zone
In four cases (0.86%), the incisions extended about 1 mm into the clear zone. In no case was the visual axis involved. Two of these cases involved extremely nervous patients who closed their eyes just as an incision was being made, dislodging the front-and-back cutting diamond knife into the clear zone.
One case was a reoperation in which a backcutting incision was made with a faulty blade.
In the fourth case, the clear zone demarcation was difficult to detect as an uphill incision was being made with the aid of the Krumeich radial keratotomy bridge.
None of these cases showed any visual acuity loss, and there were no postoperative complications.
Early Postoperative Complications
We noticed a few cases of slight choroidal reaction with some pain, which disappeared after 1 or 2 days with eye drops, but no cases of significant inflammation of the cornea occurred. No cases of bacterial ulcer or endophthalmitis were seen.
Intraoperative complications in this study included microperforations (3.8%), macroperforations (1.5%), and incisions into the clear zone (0.86%), for a total complication rate of 6.16%.
None of the complications led to a loss of best corrected visual acuity.
We compared our study with previous publications, particularly that of Rashid and Waring.8 They reported a rate of small perforations with centrifugal incisions between 2% and 10% (2.3% in the PERK study). Our rate was 1.62% with centrifugal incisions. The rate of larger perforations is reported from 0% to 0.45%; our rate was 0.2% with centrifugal incisions.
Complications occurred much more often with the centripetal technique or when the surgeon switched from centrifugal to centripetal incisions. Centripetal cuts are deeper, especially near the clear zone. This is probably the reason we observed more microperforations with this technique, especially since the same blade setting was used with both centripetal and centrifugal cuts. It is likely that more macroperforations were seen in centripetal incisions because it is more difficult to detect the initial perforation with this technique. However, our results were better with centripetal incisions for myopias of 5.00 D or more.7
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2. Leroux les Jardins S, Massin M. Comparison of visual axis determination with the microscope light or with a specific glass-fiber device. Eur J Implant RefSurg. 1989;1:181-184.
3. Hofmann RF, Lindstrom RL. Radial Keratotomy, Surgical Technique. Th orofare, NJ: SLACK Incorporated; 1986:69-87.
4. Neumann AC, McCarty GR. Fyodorov technique: limbus to optical zone cutting. In: Sanders DR, (ed). Radial Keratotomy, Surgical Technique. Thorofare, NJ: SLACK, Incorporated; 1986: 69-87.
5. Franks S. Radial keratotomy undercorrection: a new approach. Journal of Refractive Surgery. 1986;14:171-173.
6. Thornton SR Thornton guide for radial keratotomy incisions and optical zone size. Journal of Refractive Surgery. 1985;1:28-31.
7. Leroux les Jardins S, Frisch E, Bertrand I, Massin M. Les limites actuelles de la Radiaire, Ophtalmologie. 1990;4:346349.
8. Rashid ER, Waring GO. Complications of radial and transverse keratotomy. Surv Ophthalmol. 1989;34:73- 106,222.