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An Adjustable Single Running Suture Technique to Reduce Postkeratoplasty Astigmatism
An Adjustable Single Running Suture Technique to Reduce Postkeratoplasty Astigmatism A Preliminary Report DAVID T. C. LIN, MD, FRCS(C)/ STEVEN E. WILSON, MD,t JAMES J. REIDY, MD,t STEPHEN D. KLYCE, PhD, 1 MARGUERITE B. McDONALD, MD, l HERBERT E. KAUFMAN, MD,l JAMES I. McNEILL, MD2
Abstract: The authors compared postkeratoplasty astigmatism over a 4-month period after surgery in a randomized, prospective study of two groups of patients (total N = 18) who received two different suture techniques. The test group (N = 8) had a single running suture with postoperative suture adjustment; on the basis of computer-assisted topographic analysis, the suture was tightened in the flatter meridian and loosened in the steeper meridian in the first month after surgery. The control group (N = 10) had a standard double running suture procedure with no postoperative adjustment; the single running 10-0 nylon suture was removed 3 months after surgery. Four months after penetrating keratoplasty, mean (± standard deviation) astigmatism in the test group was 1.7 ± 0.7 diopters (0), and all patients had less than 2.6 0 of astigmatism. In the control group, mean astigmatism was significantly higher (5.4 ± 2.4 0; range, 0.7-9.0 0; P < 0.01). The results suggest that postkeratoplasty astigmatism can be reduced with the single running suture technique accompanied by postoperative suture adjustment. Ophthalmology 1990; 97:934-938
Corneal astigmatism remains a major problem in visual rehabilitation after uncomplicated penetrating keratoplasty. Many factors contribute to this problem. Some that are potentially modifiable include the disparity in the sizes of the trephines used to cut the donor tissue and recipient bed, the diameter of the graft, and the suture technique. 1,2
Various suturing techniques designed to reduce postkeratoplasty astigmatism have been proposed. In the late 1970s, McNeill and Kaufman 3 reported the use of double running sutures to permit early visual rehabilitation after keratoplasty. Removal of the 10-0 nylon suture in this procedure, however, has been shown to result in unpredictable changes in astigmatism. 4,5 More recently, Binde~ Presented in part as a poster at the American Academy of Ophthalmology Annual Meeting, New Orleans, Ocl/Nov, 1989.
Originally received: December 18, 1989. Revision accepted: February 23, 1990. LSU Eye Center, Louisiana State University Medical Center School of Medicine, New Orleans. 2 Department of Ophthalmology, Loma linda University, Loma linda. Dr. lin is currently affiliated with the Department of Ophthalmology, The University of British Columbia, Vancouver. Dr. Wilson is currently affiliated with the Department of Ophthalmology, University of Texas Southwestem Medical Center at Dallas. 1
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Supported in part by US Public Health Service grants EY02580, E403311, and EY02377 from the National Eye Institute, National Institutes of Health, Bethesda, Maryland, and a postdoctoral fellowship (Dr. lin) from the British Columbia Health Care Research Fund, British Columbia, Canada. None of the authors has a proprietary or financial interest in any of the products or companies mentioned in this study. Reprint requests to Herbert E. Kaufman, MD, LSU Eye Center, 2020 Gravier St, Suite B, New Orleans, LA 70112.
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Fig 1. Top left. absolute scale color-coded topographic map 10 of a cornea in the test group til a: w • PRE ADJUSTMENT 2 weeks after penetrating • 4 MO POSTOPERATIVE Ii: keratoplasty. The map shows o c 8.5 0 of astigmatism and ~ paracentral surface irregularity superotemporal to the visual axis. The color-coded dioptric scale is on the right of the figure. Second row left. schematic drawing demonstrates the method of suture adjustment used to reduce astigmatism shown in the above map. Open arrows point to the steepest meridian (warm colors in above figure). The suture is grasped with Tenant tying forceps at the flatter meridian approximately represented by the midpoints of the curved double-headed arrows on both sides of the cornea (cool colors in above figure). On opposite sides of the flattest meridian, the suture is gently pulled up perpendicular to the corneal surface to tighten and create slack in the suture. Slack is moved toward the steeper meridian by redistributing it in the direction of the small arrows along the suture bites in both directions. Third row left. absolute scale color-coded topographic map of the same cornea 1 month after suture adjustment. Residual astigmatism is 1.8 O. The axis has shifted approximately 60° from the location of the axis before suture adjustment. Fig 2. Bottom left. mean astigmatism of the test group with the single-running suture (SS; striped bar) compared to that of the control group with the double-running suture (OS; solid bar) at POSTOPERATIVE MONTH 1, 2, 3, and 4 monthsafter penetrating keratoplasty. Fig 3. Top right. corneal astigmatism for each patient in the test group before suture adjustment (solid bar) and 4 months after keratoplasty (striped bar). Fig 4. Second row right, absolute scale color-coded topography map of a cornea in the test group before suture adjustment shows 6.8 0 of astigmatism with the steep meridian at approximately 125° (simulated keratometry [Sim K] = 46.3 X 125°/39.5 X 35°). There also is central irregular astigmatism. Third row right. topographic map of the same cornea I month after suture adjustment shows 1.4 0 Of astigmatism (Sim K ~ 46.1 X 9r/44.7 X 7°). Bottom right. topographic map of the same cornea approximately 3 months after suture adjustment shows 1.80 of astigmatism (Sim K = 45 .7 X 93 °/43.9 X 3°). These three figures demonstrate that there was little change in the topographic pattern over the 3-month observation period after suture adjustment.
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decreased astigmatism using a combination of interrupted and running sutures. In 1989, McNeill and Wessels 7 described a technique of suture adjustment involving redistribution of tension in a single running suture, with retrospective results showing a significant decrease in post keratoplasty astigmatism. The purpose of our study was to compare prospectively the amount of postkeratoplasty astigmatism produced by a slightly modified version of the McNeill/ Wessels technique with that produced by a standard double running suture technique.
PATIENTS AND METHODS One eye each of 18 patients undergoing penetrating keratoplasty at the LSU Eye Center was assigned prospectively to one of two groups using a table of random numbers. The test group had a single running suture procedure with suture adjustment in the first postoperative month. The control group had a standard double running suture with no adjustment. Each case in both groups was operated on by one of four surgeons (DTCL, SEW, ]JR, or HEK). Each participating surgeon did an approximately equal proportion of surgeries in the suture adjustment and control group. Each surgeon had limited experience with the suture adjustment technique in a few cases before the initiation of this study. Informed consent was obtained from all patients before inclusion in the study. In both groups, penetrating keratoplasty was done normally, including the use of a McNeill-Goldman scleral fixation ring, trephination of the host corneal bed with a 7.5-mm Hessburg-Barron vacuum suction trephine, and trephination of the donor tissue from the endothelial side with an 8.0-mm disposable trephine and punch (Weck, Princeton, NJ). Partial-thickness trephination of the host cornea was followed by imprinting of suture placement marks by means of a Lin 16-mark corneal suture marker (Storz, St. Louis, MO) and placement of four interrupted 10-0 nylon cardinal sutures. In the test group, the wound was closed with a 16-bite 10-0 nylon running suture. In the control group, the wound was closed with a 16-bite 10-0 nylon suture followed by a 16-bite 11-0 nylon running suture. In both groups, the running sutures were passed deeply into the corneal stroma near Descemet's membrane, the knots were buried in the wound, and the cardinal sutures were removed after placement of the 10-0 nylon suture. Postoperative medications included topical prednisolone acetate 1 %at tapering doses and topical gentamicin sulfate 0.3% drops three or four times daily for the first postoperative month. All patients were seen at least weekly for the first 4 weeks after surgery. Topographic analysis was done using the Corneal Modeling System 8 (Computed Anatomy, Inc, New York, NY) 1 to 2 weeks after surgery, monthly thereafter for all patients, and before suture adjustment for the test group. One drop of artificial tears solution was placed on the 936
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cornea before each examination to improve the quality of the mires. Only photokeratoscope images with accurate processing during analysis were included. All reported astigmatism values were calculated using computerized algorithms to determine the simulated keratometry value. 9 - 11 Standard keratometer measurements (American Optical, Keene, NH) yielded similar values for the corneas that had sufficiently regular surfaces to permit valid keratometer measurements to be obtained in the early postoperative period. In the test group, if corneal astigmatism was greater than 2.5 diopters (D) 1 week to 1 month after surgery, the sutures were adjusted at the slit lamp using the Corneal Modeling System absolute scale color-coded contour maps8 as a guide (Fig 1). With the patient comfortably positioned at the slit lamp, the cornea was anesthetized with topical proparacaine 0.5%. In some cases, a wire lid speCUlum was used to facilitate the procedure. The suture was grasped with Tenant tying forceps at the flatter meridian (cool colors on the color-coded topographic map; Fig I) and tightened in both directions so that it could be redistributed and loosened at the previously steeper meridian approximately 90° away (warm colors on map). The platforms of the tying forceps were positioned parallel to the suture. Care was taken to pull the suture in the direction of the suture tract to prevent unnecessary bending. The suture was adjusted around the knot. In the process of tightening the sutures, small epithelial defects were produced where the suture was lifted away from the cornea. Prophylactic topical gentamicin sulfate 0.3% was administered routinely before and after suture manipulation. The eyes were not patched after suture adjustment. In the control group, the 10-0 nylon running suture was removed in the third postoperative month. The cornea was anesthetized with proparacaine 0.5% and prophylactic gentamicin sulfate 0.3% was applied before and after suture removal. Alternate bites of the 10-0 nylon suture were cut with a stainless steel blade (#75 Beaver, Belmont, MA), and the remaining fragments were removed with a jeweler's forceps. Care was taken not to break the 11-0 nylon suture, which was left in place. Mean astigmatism for the test and control groups was compared at monthly intervals. Statistical comparisons between groups and within a group were analyzed using the Mann-Whitney U test. A P value < 0.05 was considered statistically significant. Errors were expressed as standard deviations.
RESULTS From November 1988 to February 1989, 18 eyes of 18 patients were randomized to two groups, eight in the test group, and ten in the control group. In order of decreasing frequency, pseudophakic bullous keratopathy, aphakic bullous keratopathy, failed graft, Fuchs' dystrophy, and interstitial keratitis accounted for 90% of the diagnoses;
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ADJUSTABLE SUTURE TECHNIQUE TO REDUCE POSTKERATOPLASTY ASTIGMATISM
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Fig S. Corneal astigmatism for each patient in the control group before suture removal 3 months postoperatively (solid bar) and I month after suture removal (striped bar).
there was no significant difference between the test and control groups. Patients with keratoconus were excluded from the study. During the first month after surgery, the eight eyes in the test group underwent suture adjustment, with the result assessed by means of corneal topographic analysis, until astigmatism was reduced to less than 2.5 D. At most, two or three adjustments were necessary at each visit. If total astigmatism was greater than 2.5 0 at subsequent visits, the suture was adjusted again. Five eyes (62.5%) required manipulation at only one visit, two eyes (25%) required manipulation at two visits, and one eye (12.5%) required manipulation at three visits. No suture was adjusted after the first postoperative month. Mean astigmatism in the two groups at 1, 2, 3, and 4 months after surgery is shown in Figure 2. In the first month (before suture adjustment in the test group), there was no significant difference between the groups (P > 0.58); mean astigmatism was 6.7 ± 2.3 0 in the test group and 5.9 ± 2.4 0 in the control group. In the second month (after suture adjustment in the test group), mean astigmatism was significantly less (P < 0.005) in the test group (1.9 ± 0.6 D) compared with the control group (5.5 ± 2.5 D). No significant change in mean astigmatism was seen in either the test group or the control group at 3 or 4 months compared with the 2-month value. The difference in mean astigmatism between the test and control groups remained significant (P < 0.01) at each interval to the end of the study. A comparison of the preadjustment astigmatism and the 4-month value for each patient in the test group is shown in Figure 3. The overall mean change from 6.7 ± 2.3 D to 1.7 ± 0.6 D was significant (P < 0.005). Before suture adjustment, three of the eight eyes (37.5%) had more than 8 D of astigmatism, four (50%) had 4 to 8 0 , and one (12.5%) had less than 4 D . Four months after penetrating keratoplasty (3 months after suture adjustment), all eyes in the test group had less than 2.6 0 of astigmatism. In Figure 4, color-coded contour maps illustrate the stability of corneal configuration in one of the eyes in the test group 3 months after suture adjustment. A comparison of the presuture-removal astigmatism and the 4-month value for each patient in the control
group is shown in Figure 5. The overall mean change from 5.4 ± 2.4 0 to 4.8 ± 2.6 D was not significant. Before suture removal, one of the ten eyes (10%) had more than 8 0 of astigmatism, eight (80%) had 4 to 8 0 , and one (10%) had less than 4 D .After suture removal, seven (70%) of the eyes showed a decrease in astigmatism, and three (30%) showed an increase. Four months after penetrating keratoplasty (1 month after suture removal), one eye (10%) had more than 8 D of astigmatism, five (50%) had between 4 and 8 D, and four (4%) had less than 4 D . These results illustrate the unpredictable changes in astigmatism after suture removal at the third postoperative month in patients with a double running suture.
DISCUSSION This prospective study was designed to evaluate a new technique described by McNeill and Wessels 7 (in which a single running 10-0 nylon suture was adjusted postoperatively) and to cOmpare this method with a wellestablished double running suture technique.3 Four months after surgery (3 months after suture adjustment), mean astigmatism in the test group (1.7 ± 0.6 D) was significantly less than that in the control group (4.8 ± 2.6 D). The retrospective results described by McNeill and Wessels 7 were similar. Between 3 and 6 months after surgery, the mean astigmatism in the suture adjustment group was 2.87 ± 1.87 D compared with 4.80 ± 3.13 D in the control groups without suture adjustment. In our study, all suture adjustments were completed within the first month after surgery, and all eyes in the test group had less than 2.6 D of residual astigmatism 4 months postoperatively. The original version of this technique 7 involved a running 10-0 nylon suture with 17 to 26 bites (mean, 21 bites). We standardized the suture pattern to 16 bites using a Lin marker. More symmetric spacing of the sutures facilitated adjustment and minimized localized compressive forces. Since this study was completed, we have also used 24-bite single running 10-0 nylon sutures with similar results. One of the reported advantages of using a double running suture technique is early visual rehabilitation. 3,4,'2 Removal of the 10-0 nylon running suture 3 months postoperatively usually provides a stable refraction and useful vision 1 month later. The disadvantage of this technique is the lack of control over astigmatism. Our results confirm previously published reports of unpredictable changes in astigmatism after removal of the 10onylon suture in the double running suture technique.4,5. '2 Many surgical techniques have been described to correct postkeratoplasty astigmatism. 1,2,4,6,12,13 A major problem with these techniques is irreversibility and lack of predictability. For example, selective removal of interrupted sutures has been shown to decrease postkeratoplasty astigmatism,2,6 but the results are not predictable, and the procedure requires increased numbers of postoperative visits. Selective removal of a tight suture com937
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monly results in an overcorrection of effect, with relative steepening 90° away, which makes it necessary to remove additional sutures on subsequent visits. Other complications related to selective suture rem.oval include wound dehiscence, suture-induced irritation, vascularization, and infection. 12 Although relaxing incisions and wedge resections can correct postkeratoplasty astigmatism, these procedures cannot be reversed easily and are usually reserved for patients who have had all sutures removed. Large underand overcorrections often occur with these techniques. 14,15 Other potential problems include inadvertent perforations with relaxing incisions and prolonged healing times with wedge resections. 14 Computer-assisted topographic maps were used to guide suture adjustment and to document topographic alterations. Regional differences in corneal topography can be depicted better with color-coded maps than by keratometry. 16 Additionally, documentation with color-coded maps helps to avoid adjustment on the wrong axis; the adjustments are always made beginning with the cool colors and proceeding toward the warm colors. Lack of computer-assisted topographic analysis does not, however, preclude use of the technique of postkeratoplasty suture adjustment. Keratometry mires, placido discs, or photokeratoscopes can be used, although information derived from these is limited. 10 In this small series, no cases of suture breakage, infection, or wound dehiscence were noted. These are potential complications that are likely to arise in larger series. McNeill and Wessels? reported a suture breakage rate of less than 2.5% in 330 eyes. When breakage occurs, the running suture can be spliced easily; however, the additional knots may complicate suture adjustment. Careful manipulation with smooth-tipped forceps decreased the risk of breakage. Application of prophylactic antibiotics is recommended to decrease the risk of infection after suture adjustment since small epithelial defects created by lifting the suture are unavoidable. Also, although we have not seen any corneal allograft rejections in these patients, we now increase topical corticosteroids for several days after suture adjustment. In this study, all sutures were adjusted within the first postoperative month. Although it is likely that larger changes in corneal topography are easier to achieve during the early postoperative period, we successfully adjusted single running 10-0 nylon sutures up to 9 months after penetrating keratoplasty in patients who were not enrolled in this study. The longer the period of time after surgery, however, the greater the risk of suture breakage during adjustment, because of biodegradation of the nylon suture. Long-term studies are needed to evaluate the long-term stability of this procedure. The changes induced by suture adjustment appear to remain stable for at least 3 months, but topographic alterations with a recurrence of astigmatism may occur with wound healing or if the 10-0 running nylon suture is removed. McNeill and Wessels? showed that mean astigmatism remained lower in the patients with the new technique even after the single running suture was removed compared with a control group of 938
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patients with a single running suture and no suture adjustment. Although it is appealing to consider the use of a suture that is resistant to biodegradation, such as polyester, we found that this material is inadequate because oflow elasticity and a tendency to "cheese-wire" through the tissue during adjustment. The development of a suture material that is nonreactive, has elasticity similar to that of nylon, and is resistant to biodegradation would facilitate the suture adjustment technique.
ACKNOWLEDGMENTS The Corneal Modeling System used in this study was supplied by Computed Anatomy Inc., New York, New York.
REFERENCES 1. Swinger CA. Postoperative astigmatism. Surv Ophthalmol 1987; 31: . 219-48. 2. Binder PS. Controlled reduction of postkeratoplasty astigmatism. In: Brightbill FS, ed. Comeal Surgery: Theory, Technique, and Tissue. St. Louis: CV Mosby, 1986; 326-32. 3. McNeill JI, Kaufman HE. A double running suture technique for keratoplasty: earlier visual rehabilitation. Ophthalmic Surg 1977; 8:5861. 4. Musch DC, Meyer RF, Sugar A. The effect of removing running sutures on astigmatism after penetrating keratoplasty. Arch Ophthalmol1988; 106:488-92. 5. Lin OTC, Wilson SE, Reidy JJ, et al. Topographic changes that occur with 10-0 nylon suture removal following keratoplasty. Refract Comeal Surg 1990; 6:21-5. 6. Binder PS. The effect of suture removal on postkeratoplasty astigmatism. Am J Ophthalmol1988; 105:637-45. 7. McNeill JI, Wessels IF. Adjustment of single continuous suture to control astigmatism after penetrating keratoplasty. Refract Comeal Surg 1989; 5:216-23. 8. Gormley OJ, Gersten M, Koplin RS, Lubkin V. Comeal modeling. Cornea 1988; 7:30-5. 9. Oingeldein SA, Klyce SO, Wilson SE. Quantitative descriptors of comeal shape derived from computer-assisted analYSis of photokeratographs. Refract Comeal Surg 1989; 5:372-8. 10. Wilson SE, Wang JY, Klyce SO. Quantitative and mathematical analysis of photokeratoscopic images. In: Schanzlin OJ, Robin J, eds. Comeal Topography. New York: Springer-Verlag (in press). 11. Wilson SE, Lin OTC, Klyce SO, et al. Topographic changes in contact lens-induced comeal warpage. Ophthalmology 1990; 97:(6)734-44. 12. Musch DC, Meyer RF, Sugar A, Soong HK. Comeal astigmatism after penetrating keratoplasty: the role of suture technique. Ophthalmology 1989; 96:698-703. 13. Olson RJ. Prevention of astigmatism in comeal transplant surgery. Int Ophthalmol Clin 1988; 28:37-45. 14. Krachmer JH, Fenzl RE. Surgical correction of high postkeratoplasty astigmatism: relaxing incisions vs wedge resection. Arch Ophthalmol 1980; 98:1400-2. 15. Lundergan MK, Rowsey JJ. Relaxing incisions. Comeal topography. Ophthalmology 1985; 92:1226-36. 16. Lin OTC, Wilson SE, Klyce SO. Alteration of comeal topography by refractive keratoplasty. In: Beuerman RW, Crosson CE, Kaufman HE, eds. Healing Processes in the Comea. The Woodlands, TX: Portfolio, 1989; 183-93. (Advances in applied biotechnology series; vol. 1).
Abstract: The authors compared postkeratoplasty astigmatism over a 4-month period after surgery in a randomized, prospective study of two groups of patients (total N = 18) who received two different suture techniques. The test group (N = 8) had a single running suture with postoperative suture adjustment; on the basis of computer-assisted topographic analysis, the suture was tightened in the flatter meridian and loosened in the steeper meridian in the first month after surgery. The control group (N = 10) had a standard double running suture procedure with no postoperative adjustment; the single running 10-0 nylon suture was removed 3 months after surgery. Four months after penetrating keratoplasty, mean (± standard deviation) astigmatism in the test group was 1.7 ± 0.7 diopters (0), and all patients had less than 2.6 0 of astigmatism. In the control group, mean astigmatism was significantly higher (5.4 ± 2.4 0; range, 0.7-9.0 0; P < 0.01). The results suggest that postkeratoplasty astigmatism can be reduced with the single running suture technique accompanied by postoperative suture adjustment. Ophthalmology 1990; 97:934-938
Corneal astigmatism remains a major problem in visual rehabilitation after uncomplicated penetrating keratoplasty. Many factors contribute to this problem. Some that are potentially modifiable include the disparity in the sizes of the trephines used to cut the donor tissue and recipient bed, the diameter of the graft, and the suture technique. 1,2
Various suturing techniques designed to reduce postkeratoplasty astigmatism have been proposed. In the late 1970s, McNeill and Kaufman 3 reported the use of double running sutures to permit early visual rehabilitation after keratoplasty. Removal of the 10-0 nylon suture in this procedure, however, has been shown to result in unpredictable changes in astigmatism. 4,5 More recently, Binde~ Presented in part as a poster at the American Academy of Ophthalmology Annual Meeting, New Orleans, Ocl/Nov, 1989.
Originally received: December 18, 1989. Revision accepted: February 23, 1990. LSU Eye Center, Louisiana State University Medical Center School of Medicine, New Orleans. 2 Department of Ophthalmology, Loma linda University, Loma linda. Dr. lin is currently affiliated with the Department of Ophthalmology, The University of British Columbia, Vancouver. Dr. Wilson is currently affiliated with the Department of Ophthalmology, University of Texas Southwestem Medical Center at Dallas. 1
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Supported in part by US Public Health Service grants EY02580, E403311, and EY02377 from the National Eye Institute, National Institutes of Health, Bethesda, Maryland, and a postdoctoral fellowship (Dr. lin) from the British Columbia Health Care Research Fund, British Columbia, Canada. None of the authors has a proprietary or financial interest in any of the products or companies mentioned in this study. Reprint requests to Herbert E. Kaufman, MD, LSU Eye Center, 2020 Gravier St, Suite B, New Orleans, LA 70112.
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Fig 1. Top left. absolute scale color-coded topographic map 10 of a cornea in the test group til a: w • PRE ADJUSTMENT 2 weeks after penetrating • 4 MO POSTOPERATIVE Ii: keratoplasty. The map shows o c 8.5 0 of astigmatism and ~ paracentral surface irregularity superotemporal to the visual axis. The color-coded dioptric scale is on the right of the figure. Second row left. schematic drawing demonstrates the method of suture adjustment used to reduce astigmatism shown in the above map. Open arrows point to the steepest meridian (warm colors in above figure). The suture is grasped with Tenant tying forceps at the flatter meridian approximately represented by the midpoints of the curved double-headed arrows on both sides of the cornea (cool colors in above figure). On opposite sides of the flattest meridian, the suture is gently pulled up perpendicular to the corneal surface to tighten and create slack in the suture. Slack is moved toward the steeper meridian by redistributing it in the direction of the small arrows along the suture bites in both directions. Third row left. absolute scale color-coded topographic map of the same cornea 1 month after suture adjustment. Residual astigmatism is 1.8 O. The axis has shifted approximately 60° from the location of the axis before suture adjustment. Fig 2. Bottom left. mean astigmatism of the test group with the single-running suture (SS; striped bar) compared to that of the control group with the double-running suture (OS; solid bar) at POSTOPERATIVE MONTH 1, 2, 3, and 4 monthsafter penetrating keratoplasty. Fig 3. Top right. corneal astigmatism for each patient in the test group before suture adjustment (solid bar) and 4 months after keratoplasty (striped bar). Fig 4. Second row right, absolute scale color-coded topography map of a cornea in the test group before suture adjustment shows 6.8 0 of astigmatism with the steep meridian at approximately 125° (simulated keratometry [Sim K] = 46.3 X 125°/39.5 X 35°). There also is central irregular astigmatism. Third row right. topographic map of the same cornea I month after suture adjustment shows 1.4 0 Of astigmatism (Sim K ~ 46.1 X 9r/44.7 X 7°). Bottom right. topographic map of the same cornea approximately 3 months after suture adjustment shows 1.80 of astigmatism (Sim K = 45 .7 X 93 °/43.9 X 3°). These three figures demonstrate that there was little change in the topographic pattern over the 3-month observation period after suture adjustment.
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decreased astigmatism using a combination of interrupted and running sutures. In 1989, McNeill and Wessels 7 described a technique of suture adjustment involving redistribution of tension in a single running suture, with retrospective results showing a significant decrease in post keratoplasty astigmatism. The purpose of our study was to compare prospectively the amount of postkeratoplasty astigmatism produced by a slightly modified version of the McNeill/ Wessels technique with that produced by a standard double running suture technique.
PATIENTS AND METHODS One eye each of 18 patients undergoing penetrating keratoplasty at the LSU Eye Center was assigned prospectively to one of two groups using a table of random numbers. The test group had a single running suture procedure with suture adjustment in the first postoperative month. The control group had a standard double running suture with no adjustment. Each case in both groups was operated on by one of four surgeons (DTCL, SEW, ]JR, or HEK). Each participating surgeon did an approximately equal proportion of surgeries in the suture adjustment and control group. Each surgeon had limited experience with the suture adjustment technique in a few cases before the initiation of this study. Informed consent was obtained from all patients before inclusion in the study. In both groups, penetrating keratoplasty was done normally, including the use of a McNeill-Goldman scleral fixation ring, trephination of the host corneal bed with a 7.5-mm Hessburg-Barron vacuum suction trephine, and trephination of the donor tissue from the endothelial side with an 8.0-mm disposable trephine and punch (Weck, Princeton, NJ). Partial-thickness trephination of the host cornea was followed by imprinting of suture placement marks by means of a Lin 16-mark corneal suture marker (Storz, St. Louis, MO) and placement of four interrupted 10-0 nylon cardinal sutures. In the test group, the wound was closed with a 16-bite 10-0 nylon running suture. In the control group, the wound was closed with a 16-bite 10-0 nylon suture followed by a 16-bite 11-0 nylon running suture. In both groups, the running sutures were passed deeply into the corneal stroma near Descemet's membrane, the knots were buried in the wound, and the cardinal sutures were removed after placement of the 10-0 nylon suture. Postoperative medications included topical prednisolone acetate 1 %at tapering doses and topical gentamicin sulfate 0.3% drops three or four times daily for the first postoperative month. All patients were seen at least weekly for the first 4 weeks after surgery. Topographic analysis was done using the Corneal Modeling System 8 (Computed Anatomy, Inc, New York, NY) 1 to 2 weeks after surgery, monthly thereafter for all patients, and before suture adjustment for the test group. One drop of artificial tears solution was placed on the 936
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cornea before each examination to improve the quality of the mires. Only photokeratoscope images with accurate processing during analysis were included. All reported astigmatism values were calculated using computerized algorithms to determine the simulated keratometry value. 9 - 11 Standard keratometer measurements (American Optical, Keene, NH) yielded similar values for the corneas that had sufficiently regular surfaces to permit valid keratometer measurements to be obtained in the early postoperative period. In the test group, if corneal astigmatism was greater than 2.5 diopters (D) 1 week to 1 month after surgery, the sutures were adjusted at the slit lamp using the Corneal Modeling System absolute scale color-coded contour maps8 as a guide (Fig 1). With the patient comfortably positioned at the slit lamp, the cornea was anesthetized with topical proparacaine 0.5%. In some cases, a wire lid speCUlum was used to facilitate the procedure. The suture was grasped with Tenant tying forceps at the flatter meridian (cool colors on the color-coded topographic map; Fig I) and tightened in both directions so that it could be redistributed and loosened at the previously steeper meridian approximately 90° away (warm colors on map). The platforms of the tying forceps were positioned parallel to the suture. Care was taken to pull the suture in the direction of the suture tract to prevent unnecessary bending. The suture was adjusted around the knot. In the process of tightening the sutures, small epithelial defects were produced where the suture was lifted away from the cornea. Prophylactic topical gentamicin sulfate 0.3% was administered routinely before and after suture manipulation. The eyes were not patched after suture adjustment. In the control group, the 10-0 nylon running suture was removed in the third postoperative month. The cornea was anesthetized with proparacaine 0.5% and prophylactic gentamicin sulfate 0.3% was applied before and after suture removal. Alternate bites of the 10-0 nylon suture were cut with a stainless steel blade (#75 Beaver, Belmont, MA), and the remaining fragments were removed with a jeweler's forceps. Care was taken not to break the 11-0 nylon suture, which was left in place. Mean astigmatism for the test and control groups was compared at monthly intervals. Statistical comparisons between groups and within a group were analyzed using the Mann-Whitney U test. A P value < 0.05 was considered statistically significant. Errors were expressed as standard deviations.
RESULTS From November 1988 to February 1989, 18 eyes of 18 patients were randomized to two groups, eight in the test group, and ten in the control group. In order of decreasing frequency, pseudophakic bullous keratopathy, aphakic bullous keratopathy, failed graft, Fuchs' dystrophy, and interstitial keratitis accounted for 90% of the diagnoses;
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ADJUSTABLE SUTURE TECHNIQUE TO REDUCE POSTKERATOPLASTY ASTIGMATISM
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PRE SUTIJRE REMOVAL POST SUTURE REMOVAL
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Fig S. Corneal astigmatism for each patient in the control group before suture removal 3 months postoperatively (solid bar) and I month after suture removal (striped bar).
there was no significant difference between the test and control groups. Patients with keratoconus were excluded from the study. During the first month after surgery, the eight eyes in the test group underwent suture adjustment, with the result assessed by means of corneal topographic analysis, until astigmatism was reduced to less than 2.5 D. At most, two or three adjustments were necessary at each visit. If total astigmatism was greater than 2.5 0 at subsequent visits, the suture was adjusted again. Five eyes (62.5%) required manipulation at only one visit, two eyes (25%) required manipulation at two visits, and one eye (12.5%) required manipulation at three visits. No suture was adjusted after the first postoperative month. Mean astigmatism in the two groups at 1, 2, 3, and 4 months after surgery is shown in Figure 2. In the first month (before suture adjustment in the test group), there was no significant difference between the groups (P > 0.58); mean astigmatism was 6.7 ± 2.3 0 in the test group and 5.9 ± 2.4 0 in the control group. In the second month (after suture adjustment in the test group), mean astigmatism was significantly less (P < 0.005) in the test group (1.9 ± 0.6 D) compared with the control group (5.5 ± 2.5 D). No significant change in mean astigmatism was seen in either the test group or the control group at 3 or 4 months compared with the 2-month value. The difference in mean astigmatism between the test and control groups remained significant (P < 0.01) at each interval to the end of the study. A comparison of the preadjustment astigmatism and the 4-month value for each patient in the test group is shown in Figure 3. The overall mean change from 6.7 ± 2.3 D to 1.7 ± 0.6 D was significant (P < 0.005). Before suture adjustment, three of the eight eyes (37.5%) had more than 8 D of astigmatism, four (50%) had 4 to 8 0 , and one (12.5%) had less than 4 D . Four months after penetrating keratoplasty (3 months after suture adjustment), all eyes in the test group had less than 2.6 0 of astigmatism. In Figure 4, color-coded contour maps illustrate the stability of corneal configuration in one of the eyes in the test group 3 months after suture adjustment. A comparison of the presuture-removal astigmatism and the 4-month value for each patient in the control
group is shown in Figure 5. The overall mean change from 5.4 ± 2.4 0 to 4.8 ± 2.6 D was not significant. Before suture removal, one of the ten eyes (10%) had more than 8 0 of astigmatism, eight (80%) had 4 to 8 0 , and one (10%) had less than 4 D .After suture removal, seven (70%) of the eyes showed a decrease in astigmatism, and three (30%) showed an increase. Four months after penetrating keratoplasty (1 month after suture removal), one eye (10%) had more than 8 D of astigmatism, five (50%) had between 4 and 8 D, and four (4%) had less than 4 D . These results illustrate the unpredictable changes in astigmatism after suture removal at the third postoperative month in patients with a double running suture.
DISCUSSION This prospective study was designed to evaluate a new technique described by McNeill and Wessels 7 (in which a single running 10-0 nylon suture was adjusted postoperatively) and to cOmpare this method with a wellestablished double running suture technique.3 Four months after surgery (3 months after suture adjustment), mean astigmatism in the test group (1.7 ± 0.6 D) was significantly less than that in the control group (4.8 ± 2.6 D). The retrospective results described by McNeill and Wessels 7 were similar. Between 3 and 6 months after surgery, the mean astigmatism in the suture adjustment group was 2.87 ± 1.87 D compared with 4.80 ± 3.13 D in the control groups without suture adjustment. In our study, all suture adjustments were completed within the first month after surgery, and all eyes in the test group had less than 2.6 D of residual astigmatism 4 months postoperatively. The original version of this technique 7 involved a running 10-0 nylon suture with 17 to 26 bites (mean, 21 bites). We standardized the suture pattern to 16 bites using a Lin marker. More symmetric spacing of the sutures facilitated adjustment and minimized localized compressive forces. Since this study was completed, we have also used 24-bite single running 10-0 nylon sutures with similar results. One of the reported advantages of using a double running suture technique is early visual rehabilitation. 3,4,'2 Removal of the 10-0 nylon running suture 3 months postoperatively usually provides a stable refraction and useful vision 1 month later. The disadvantage of this technique is the lack of control over astigmatism. Our results confirm previously published reports of unpredictable changes in astigmatism after removal of the 10onylon suture in the double running suture technique.4,5. '2 Many surgical techniques have been described to correct postkeratoplasty astigmatism. 1,2,4,6,12,13 A major problem with these techniques is irreversibility and lack of predictability. For example, selective removal of interrupted sutures has been shown to decrease postkeratoplasty astigmatism,2,6 but the results are not predictable, and the procedure requires increased numbers of postoperative visits. Selective removal of a tight suture com937
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monly results in an overcorrection of effect, with relative steepening 90° away, which makes it necessary to remove additional sutures on subsequent visits. Other complications related to selective suture rem.oval include wound dehiscence, suture-induced irritation, vascularization, and infection. 12 Although relaxing incisions and wedge resections can correct postkeratoplasty astigmatism, these procedures cannot be reversed easily and are usually reserved for patients who have had all sutures removed. Large underand overcorrections often occur with these techniques. 14,15 Other potential problems include inadvertent perforations with relaxing incisions and prolonged healing times with wedge resections. 14 Computer-assisted topographic maps were used to guide suture adjustment and to document topographic alterations. Regional differences in corneal topography can be depicted better with color-coded maps than by keratometry. 16 Additionally, documentation with color-coded maps helps to avoid adjustment on the wrong axis; the adjustments are always made beginning with the cool colors and proceeding toward the warm colors. Lack of computer-assisted topographic analysis does not, however, preclude use of the technique of postkeratoplasty suture adjustment. Keratometry mires, placido discs, or photokeratoscopes can be used, although information derived from these is limited. 10 In this small series, no cases of suture breakage, infection, or wound dehiscence were noted. These are potential complications that are likely to arise in larger series. McNeill and Wessels? reported a suture breakage rate of less than 2.5% in 330 eyes. When breakage occurs, the running suture can be spliced easily; however, the additional knots may complicate suture adjustment. Careful manipulation with smooth-tipped forceps decreased the risk of breakage. Application of prophylactic antibiotics is recommended to decrease the risk of infection after suture adjustment since small epithelial defects created by lifting the suture are unavoidable. Also, although we have not seen any corneal allograft rejections in these patients, we now increase topical corticosteroids for several days after suture adjustment. In this study, all sutures were adjusted within the first postoperative month. Although it is likely that larger changes in corneal topography are easier to achieve during the early postoperative period, we successfully adjusted single running 10-0 nylon sutures up to 9 months after penetrating keratoplasty in patients who were not enrolled in this study. The longer the period of time after surgery, however, the greater the risk of suture breakage during adjustment, because of biodegradation of the nylon suture. Long-term studies are needed to evaluate the long-term stability of this procedure. The changes induced by suture adjustment appear to remain stable for at least 3 months, but topographic alterations with a recurrence of astigmatism may occur with wound healing or if the 10-0 running nylon suture is removed. McNeill and Wessels? showed that mean astigmatism remained lower in the patients with the new technique even after the single running suture was removed compared with a control group of 938
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patients with a single running suture and no suture adjustment. Although it is appealing to consider the use of a suture that is resistant to biodegradation, such as polyester, we found that this material is inadequate because oflow elasticity and a tendency to "cheese-wire" through the tissue during adjustment. The development of a suture material that is nonreactive, has elasticity similar to that of nylon, and is resistant to biodegradation would facilitate the suture adjustment technique.
ACKNOWLEDGMENTS The Corneal Modeling System used in this study was supplied by Computed Anatomy Inc., New York, New York.
REFERENCES 1. Swinger CA. Postoperative astigmatism. Surv Ophthalmol 1987; 31: . 219-48. 2. Binder PS. Controlled reduction of postkeratoplasty astigmatism. In: Brightbill FS, ed. Comeal Surgery: Theory, Technique, and Tissue. St. Louis: CV Mosby, 1986; 326-32. 3. McNeill JI, Kaufman HE. A double running suture technique for keratoplasty: earlier visual rehabilitation. Ophthalmic Surg 1977; 8:5861. 4. Musch DC, Meyer RF, Sugar A. The effect of removing running sutures on astigmatism after penetrating keratoplasty. Arch Ophthalmol1988; 106:488-92. 5. Lin OTC, Wilson SE, Reidy JJ, et al. Topographic changes that occur with 10-0 nylon suture removal following keratoplasty. Refract Comeal Surg 1990; 6:21-5. 6. Binder PS. The effect of suture removal on postkeratoplasty astigmatism. Am J Ophthalmol1988; 105:637-45. 7. McNeill JI, Wessels IF. Adjustment of single continuous suture to control astigmatism after penetrating keratoplasty. Refract Comeal Surg 1989; 5:216-23. 8. Gormley OJ, Gersten M, Koplin RS, Lubkin V. Comeal modeling. Cornea 1988; 7:30-5. 9. Oingeldein SA, Klyce SO, Wilson SE. Quantitative descriptors of comeal shape derived from computer-assisted analYSis of photokeratographs. Refract Comeal Surg 1989; 5:372-8. 10. Wilson SE, Wang JY, Klyce SO. Quantitative and mathematical analysis of photokeratoscopic images. In: Schanzlin OJ, Robin J, eds. Comeal Topography. New York: Springer-Verlag (in press). 11. Wilson SE, Lin OTC, Klyce SO, et al. Topographic changes in contact lens-induced comeal warpage. Ophthalmology 1990; 97:(6)734-44. 12. Musch DC, Meyer RF, Sugar A, Soong HK. Comeal astigmatism after penetrating keratoplasty: the role of suture technique. Ophthalmology 1989; 96:698-703. 13. Olson RJ. Prevention of astigmatism in comeal transplant surgery. Int Ophthalmol Clin 1988; 28:37-45. 14. Krachmer JH, Fenzl RE. Surgical correction of high postkeratoplasty astigmatism: relaxing incisions vs wedge resection. Arch Ophthalmol 1980; 98:1400-2. 15. Lundergan MK, Rowsey JJ. Relaxing incisions. Comeal topography. Ophthalmology 1985; 92:1226-36. 16. Lin OTC, Wilson SE, Klyce SO. Alteration of comeal topography by refractive keratoplasty. In: Beuerman RW, Crosson CE, Kaufman HE, eds. Healing Processes in the Comea. The Woodlands, TX: Portfolio, 1989; 183-93. (Advances in applied biotechnology series; vol. 1).