INADEQUACY OF A POLYESTER (MERSILENE) SUTURE FOR THE REDUCTION OF ASTIGMATISM AFTER PENETRATING KERATOPLASTY* BY Bradley A. Bertram, MD (BY INVITATION), Carolyn Drews, PhD Mary Gemmill, COMT (BY INVITATION), Jose Guell, MD (BY INVITATION), Mervat Murad, MD (BY INVITATION), AND George 0. Waring, MD

(BY INVITATION),

INTRODUCTION

ASTIGMATISM

IS ONE OF THE MAJOR CONTRIBUTORS TO DECREASED VISUAL

acuity after successful penetrating keratoplasty. 12 Using currently popular techniques, mean astigmatism after penetrating keratoplasty ranges between 2.5 and 3.5 D with 45% to 48% of cases having greater than 3.0 D.3,4 Thus, a major goal is to find ways to reduce astigmatism in postoperative patients. Surgeons have turned their attention to manipulation of sutures after penetrating keratoplasty to try to control and reduce astigmatism, adjusting the suture tension to a point that minimizes astigmatism.3-6 Two techniques for adjusting the suture tension have been described: selective removal of the interrupted sutures from the steep semimeridian3-13 and adjustment of tension on a single running suture. 14-16 These techniques have been shown to successfully reduce astigmatism after penetrating keratoplasty3-16 but suffer a major disadvantage the suture must then remain in place indefinitely. If the suture biodegrades, it may loosen and be associated with epithelial defects, sterile infiltrates, microbial keratitis, or allograft rejection. If the suture is removed at any time after surgery, large changes in astigmatism may still occur, demon*From the Emory University Medical School, Department of Ophthalmology, Atlanta, Georgia. Supported by Research to Prevent Blindness departmental grant and National Institutes of Health departmental core grant P30-EY06360.

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strating that the wound cannot be "set" independent of the suture tension. 3,8,9,14,17, 18

The standard material used for suturing is nylon, usually 15 ,u (11.0) or 22 ,u (10.0) diameters. Since nylon contains water in its molecular structure, it undergoes hydrolysis during the 2 to 3 years after surgery, creating a number of potential difficulties as mentioned above. Two other suture materials are available for corneal surgery, polypropylene (ProleneR) and polyester (dacron, Mersilene). These do not hydrolyze and have been used extensively in general surgery, particularly for the permanent attachment of prostheses such as vascular grafts and cardiac valves. The advantage of a non-biodegradable suture for prolonged retention in the cornea is obvious; once the suture tension is adjusted and reaches an equilibrium in the tissue, it is likely to remain permanently in that position without subsequent changes, providing a safer, more stable longterm postoperative course. Polyester suture seems to fulfill these criteria. However, relatively little information about the safety and efficacy of using polyester sutures in penetrating keratoplasty is available. Therefore, to explore the feasibility of using polyester (Mersilene) sutures in penetrating keratoplasty, we designed two prospective studies. The first (Study 1) was a randomized comparison of combined running and interrupted polyester and nylon sutures. The second (Study 2) was a case series of a single running 10-0 or 11-0 polyester sutures with postoperative adjustment of suture tension. Throughout this paper, we use the more familiar trade name, Mersilene, for polyester sutures. MATERIALS AND METHODS

All of the cases reported in this paper were done by one surgeon (GOW) with assistance from corneal fellows. Only a single eye from any patient was included in the studies. Eyes entered into each series have avascular corneas. Those with intense vascularization or large focal peripheral traumatic scars were excluded to minimize the effect of asymmetrical healing on the amount of postoperative astigmatism. STUDY 1: COMBINED INTERRUPTED AND RUNNING MERSILENE AND NYLON SUTURES

The goal of this study was to examine the biocompatibility and behavior of nylon and Mersilene sutures after penetrating keratoplasty. Data on the effect of selectively removing interrupted sutures to reduce astigmatism was an ancillary part of this evaluation. Patients undergoing penetrating keratoplasty between December, 1987 and July, 1988, were eligible for inclusion in this portion of the study. Just

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prior to surgery, corneas were randomized to one of two treatment groups. Half of the eyes were sutured with a Mersilene 11-0 running suture; the other half received a running 11-0 nylon suture. Regardless of treatment group, all eyes also had six nylon and six Mersilene interrupted 10-0 sutures placed at the 12 clock hours. Surgical Technique All surgery was performed using regional retrobulbar and seventh cranial nerve anesthesia obtained with 0.75% bupivicaine with hyaluronidase. Aphakic and pseudophakic eyes were stabilized with a scleral support ring sutured to the episclera. The recipient bed ranged from 7.5 to 8.0 mm in diameter. The donor cornea, which was preserved in either MK or Ksol media, was cut from the endothelial side using a triconcave polycarbonate block and a disposable free-hand trephine or a Hanna suction punch block (Moria-Dugast, SA, Paris, France).19 The diameter of the donor was larger than the recipient by 0.25 mm for phakic and pseudophakic eyes and 0.50 mm for aphakic eyes. The host cornea was trephined in two methods: (1) with the Hanna suction trephine'9 and a diamond knife or (2) with a freestanding disposable Weck blade as described by van Rij and Waring20 and corneal scissors. Some patients had additional surgical procedures such as extracapsular cataract extraction, intraocular lens removal, intraocular lens insertion, gonioplasty, iridoplasty, and anterior vitrectomy (Table I). Donor buttons were sutured to the host with four interrupted 10-0 nylon sutures in the cardinal position. Two additional 10-0 nylon sutures were then placed at varying clock hours and six polyester 10-0 sutures at TABLE I: SURGICAL PROCEDURES

Penetrating keratoplasty alone Cataract extraction with posterior chamber IOL implantation Anterior vitrectomy Anterior vitrectomy with IOL

exchange Iridoplasty Secondary IOL Reposition IOL IOL, anterior vitrectomy,

INTERRUPTED-RUNNING STUDY (n = 45)

RUNNING MERSILENE STUDY (n = 23)

16 (36%) 12 (27%)

7 (30%) 6 (26%)

0 (0%) 4 (9%)

1 (4%) 8 (35%)

0 5 1 4

(0%) (11%) (2%) (9%)

1 0 0 0

(4%) (0%) (0%) (0%)

goniosynechiolysis IOL, anterior vitrectomy, goniosynechiolysis, iridoplasty Anterior and posterior vitrectomy, IOL removal,

iridoplasty IOL, intraocular lens.

2 (4%)

0 (0%)

1 (2%)

0 (0%)

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the remaining clock hours. A continuous 11-0 nylon or polyester suture was placed with 12 antitorque bites between the previous 12 interrupted sutures. The surgeon attempted to tie all sutures equally, and any sutures judged too loose or too tight by visual inspection were removed and replaced during surgery. Intraoperative keratoscopy was not used. All knots were buried in the recipient cornea. All patients received a subconjunctival injection of dexamethasone (2 mg), gentamicin (20 mg), and cefazolin (100 mg) at the conclusion of surgery. Postoperative Care

Topical corticosteroids and antibiotics in tapering dosages were used after surgery. Eyes were examined every 2 to 4 weeks after surgery using slitlamp microscopy, keratometry (Bausch & Lomb), keratography (Nidek), and manifest refraction. Interrupted sutures were selectively removed from the steep semimeridian to reduce astigmatism, as described in previous publications.3'5'6'1"112 The tension on interrupted sutures was not adjusted, but the sutures were removed if they broke or loosened excessively. The location and reason for removal of all sutures was noted. The presence or absence of the following complications were recorded by the surgeon on a standardized data sheet at each visit: infiltration, infection, broken suture, epithelial defect, neovascularization, allograft reaction, graft failure, tight suture, loose suture, cheesewiring, wound leak, dehiscence, and exposed knot. Statistical Analysis Complications arising within 9 months of surgery were analyzed. The risk of complications in Mersilene running sutures was compared with the risk in nylon sutures using a Fisher's exact chi-square. We did not control for potentially confounding factors such as age, sex, or diagnosis because of the small sample size. The risk of complications in Mersilene interrupted sutures was compared to the risk of complications in nylon interrupted sutures using a McNemar's chi-square. This comparison was made within individuals to avoid confounding as a result of individual susceptibility to complications. The number of nylon and Mersilene sutures affected by complications was also evaluated within individuals using a one-sample t-test. The risk of each complication was evaluated individually. However, two separate complication indices were created. Infiltration, infection, broken sutures, epithelial defects, neovascularization, and graft failure were considered to be related to the interaction between the suture and the tissue. These complications were combined to form an index called tissue-related complications. Tight sutures, loose sutures, cheesewiring, wound leaks,

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dehiscence, and exposed knots were assumed to be related to the ease of handling of the suture. These six complications were combined into an index known as handling-related complications. STUDY 2: SINGLE RUNNING MERSILENE SUTURE WITH POSTOPERATIVE ADJUSTMENT

This study was designed to answer two questions: (1) what is the general behavior of running Mersilene in penetrating keratoplasty, and (2) what is the efficacy of postoperative adjustment of running Mersilene in managing postoperative astigmatism? Patients undergoing penetrating keratoplasty between June, 1989 and October, 1989 were eligible for inclusion in this study. Informed consent was given. The astigmatic goal was a refractive astigmatism of less than 3.5 D. Thus we have defined astigmatic success as less than 3.5 D refractive astigmatism and astigmatic failure as greater than 4 D. Those eyes between 3.5 D and 4.0 D, inclusive, were classified as intermediate successes to better isolate the successes and failures. We have defined significant suture related complications, as they relate to astigmatic success or failure, as the following: (1) suture breakage, (2) cheesewiring of sutures, (3) extensive suture loosening requiring early removal, and (4) wound slip. Surgical Technique The technique was the same as for Study 1 with a few exceptions. The recipient bed diameter ranged from 7.75 mm to 9 mm. A Geuder motorized Microkeratron was used to trephine one eye. The diameter of the donor button was the same as the host opening for keratoconus eyes and 0.25 mm larger for phakic and pseudophakic eyes. The donor buttons were sutured at the four cardinal positions with interrupted 10-0 nylon suture on a compound curved needle. A single running 10-0 or 11-0 Mersilene suture was placed in an antitorque or radial fashion with 20 to 24 bites. The cardinal sutures were removed; the intraocular pressure was raised to normal; the running suture was tightened and tied; and the knot buried in recipient stroma. If a wound leak was present after inflation of the globe, additional 10-0 or 11-0 nylon interrupted sutures were placed. Intraoperative adjustment of sutures was not performed. All sutures were tied to approximate the edges of the wound without producing excessive tissue compression or a "barrel top" configuration to the graft. Postoperative Care Postoperative care was the same as in Study 1 with a few exceptions. Interrupted sutures, which were present in some eyes, were removed early in the postoperative course, to leave only the running suture.

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Adjustment of sutures began approximately 1 month after surgery, depending on the patient's follow-up schedule. In some cases, videokeratography was performed (Computed Anatomy). The steep semimeridian was located by identifying the axis of the plus cylinder on the refraction, the steep meridian on keratometry, and the semimeridian in which the keratography mires were indented, as described in detail by Harris and colleagues.6 If more than 3.25 D of refractive astigmatism was present, sutures were adjusted as long as the wound was stable clinically. Adjustments were performed at the slit-lamp microscope with topical proparacaine 0.5% anesthesia using a Tenant tying forcep in a manner similar to that described by McNeil and Wessels.14 Suture tension was distributed from the flat toward the steep semimeridian on a loop by loop basis. Topical antibiotic was placed at the conclusion of adjustment. Adjustment was repeated at subsequent visits if the refractive astigmatism was still greater than 3.25 D. RESULTS

STUDY 1: COMBINED INTERRUPTED AND RUNNING MERSILENE AND NYLON SUTURES

A total of 54 eyes of 51 patients were randomized for inclusion in the study. We report the outcomes in 45 eyes of 45 patients in the first 9 months after surgery. Follow-up information was incomplete on seven eyes (eg, suture removal by another physician, lost to follow-up prior to 9 months), and two eyes had primary graft failure necessitating repeat surgery within 3 months. Twenty of the 45 patients followed for at least 9 months were randomly assigned to receive Mersilene running sutures and 25 received a nylon running suture. Tables II and III present the clinical and demographic profiles of the population. Patients receiving a nylon running suture were demographically similar to those receiving a Mersilene running suture. The first 9 months after surgery, complications rarely occurred in the running suture, regardless of whether or not eyes had received one of polyester or nylon (Table IV). For example, cheesewiring occurred in 2 of the 25 eyes with a nylon running suture and in 3 of the 20 who received a polyester suture. Broken sutures occurred in five eyes; three that received a nylon suture and two that received a polyester suture. There was no evidence that any complication occurred more or less commonly in polyester sutures than in nylon sutures. The frequency of complications also did not differ between suture types when complications were grouped into those which occurred because of the interaction between the suture

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TABLE II: INDICATIONS FOR SURGERY

INTERRUPTED-RUNNING STUDY (n = 45)

Fuchs' dystrophy Keratoconus Failed graft Corneal edema Pseudophakic edema Interstitial keratitis Epithelial downgrowth Corneal decomposition Aphakic corneal edema Herpes simplex virus Astigmatism

15 8 6 6 5 3 1 1 0 0 0

RUNNING MERSILENE STUDY (n = 23)

(33%) (18%) (13%) (13%) (11%)

5 4 0 0 8

(7%) (2%) (2%) (0%) (0%) (0%)

2 0 0 2 1 1

(22%) (17%) (0%)

(0%) (35%) (9%) (0%) (0%) (9%) (4%) (4%)

and the tissue (ie, tissue-related complications) and those that occurred because of the difficulty of handling the suture during surgery (ie, handling-related complications). On the other hand, nylon interrupted sutures appeared to be less prone to complications than polyester sutures. As shown in Table V, at least one polyester suture had a tissue-related complication in 17 (38%) of the 45 eyes. Tissue-related complications affected at least one nylon suture in 13 (29%) of the 45 eyes. Similarly, handling-related complications, particularly tight sutures, also affected polyester sutures more frequently than nylon sutures. For example, at least one of the six polyester sutures was affected by a handling-related complication for 37 of the 45 eyes. Twenty-eight eyes experienced this type of complication in a nylon interrupted suture. TABLE III: DEMOGRAPHIC CHARACTERISTICS OF PATIENTS

INTERRUPTED-RUNNING STUDY (n

Age (yr) < 20 20-44 45-64 65 Mean Sex -

Male Female Eye Right Left

NO.

=

45)

RUNNING MIERSILENE STUDY (n = 23)

%

NO.

%

1 8 9 27 63

2 18 20 60

0 3 4 16 65

0 13 17 70

22 23

49 51

10 13

43 57

24 21

53 47

10 13

43 57

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TABLE IV: INCIDENCE OF COMPLICATIONS IN RUNNING SUTURES (NO. OF EYES, PERCENT) INTERRUPTED-RUNNING STUDY NYLON

(n

Tissue-related Infiltration Infection Broken Epithelial defect Neovascularization Allograft reaction Handling-related Tight suture Loose suture Cheesewiring Wound leak Dehiscence Exposed knot

=

25)

7 (28%) 0 (0%) 0 (0%) 3 (12%) 0 (0%) 2 (8%) 3 (12%) 4 (16%) 1 (4%) 1 (4%) 2 (8%) 0 (0%) 1 (4%) 1 (4%)

MERSILENE (n = 20)

P

6 (30%) 2 (10%) 0 (0%) 2 (10%) 0 (0%) 0 (0%) 2 (10%) 4 (20%) 0 (0%) 2 (10%) 3 (15%) 0 (0%) 0 (0%) 1 (5%)

1.00 0.19 1.00 1.00 1.00 0.49 1.00 1.00 1.00 0.58 0.64 1.00 1.00 1.00

RUNNING MERSILENE STUDY

6 1 3 1 3 1

(26%) (4%) (13%) (4%) (13%) (4%)

12 2 3 3 2

(52%) (9%) (13%) (13%) (9%)

As shown in Table VI, those eyes with a tissue-related complication in a nylon suture tended to have similar complications in polyester sutures; and those without a complication in a nylon suture usually did not have an affected polyester suture. For example, 26 eyes did not have a tissuerelated complication in either type of suture and 11 eyes had such complications in both types of suture. This finding suggests that patient characteristics played some role in predicting whether or not complications arose. However, polyester sutures were three times more likely to TABLE V: STUDY 1: INCIDENCE OF COMPLICATIONS IN INTERRUPTED SUTURES (NO. OF PATIENTS WITH - 1 AFFECTED INTERRUPTED SUTURE) NYLON (n = 45) (%)

Tissue-related Infiltration Infection Broken suture Epithelial defect Neovascularization Allograft reaction Handling-related Tight suture Loose suture

Cheesewiring Wound leak Dehiscence Exposed knot

13 3 1 1 1 8 0 28 28 4 4 0 0 1

(29%) (6%) (2%) (2%) (2%) (18%) (0%)

(62%) (58%) (9%) (9%) (0%) (0%) (2%)

MERSILENE (n = 45) (%)

McNEMAR'S ODDS RATIO

17 (38%) 6 (13%) 0 (0%) 2 (4%) 1 (2%) 7 (16%) 0 (0%) 37 (82%) 35 (78%) 4 (9%) 5 (11%) 1 (2%) 0 (0%)

3.0 4.0

0.16

2.0 1.0 0.7

0.56 1.00 0.65

5.5 4.0 1.0 2.0

0.01 0.02 1.00 0.56

4 (9%)

4.0

0.18

P

0.18

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be affected by tissue-related complications than nylon sutures in those eyes in which only one type of suture was affected (P = 0.16) (Table V). Similarly, given that handling-related complications arose in only one type of suture, polyester sutures were 5.5 times more likely to be affected than nylon sutures (P = 0.01 (Table V). These findings suggested that there were individuals who were susceptible to complications only in polyester sutures. STUDY 2: RUNNING MERSILENE SUTURE

Twenty-three eyes in 23 patients had an adjustable running Mersilene suture (Tables II and III). Twenty-two of 23 eyes had suture adjustment. One cornea had a persistent epithelial defect which precluded suture manipulation. The first adjustment occurred at a mean of 53 days postoperatively (range, 14 to 161 days). The average number of adjustments per eye was 2.7 (range, 1 to 6). Sixty-nine percent of the 23 eyes suffered complications (Table IV). Loose exposed suture loops appeared in 12 eyes (52%), 3 of them required "reefing" sutures.21 Three additional eyes had early removal of extensively loosened sutures at 5 to 6 months postoperatively. Suture infiltrates were identified in six eyes (26%), although none were determined to be microbial. Sutures broke in three eyes (13%). Two of these were 11-0 and one was 10-0; two broke during suture adjustment; one broke spontaneously at a point that had been manipulated 2 months after a suture adjustment. Three eyes (13%) had a partial thickness wound slip with anterior displacement of the donor; two occurred after extensively loose running sutures were removed early and one occurred 1 months postoperatively in an eye with an extensively loose suture. One of these was not treated, one was repaired at the slit-lamp microscope with interrupted sutures, and one was repaired in the operating room with wound revision. Neovascularizatioi into the donor occurred in three eyes (13%). Wound leaks were seen on the first postoperative day in three eyes (13%). Two were repaired by redistributing the tension on the suture and one with addition of an interrupted suture. Cheesewiring of the suture through the donor or host occurred in two eyes (9%). Exposed knots as a result of suture adjustment complicated two eyes. Infectious crystalline keratopathy, endothelial graft rejection, and a persistent epithelial defect were seen in one eye each. At 6 months postoperatively, the median refractive astigmatism was 3.37 D (mean, 4.03 + 2.37 D; range, 1.25 to 9.75 D). Fifty percent of eyes were considered an astigmatic success (ie, < 3.5 D astigmatism); 27% were considered an astigmatic failure (> 4.0 D). Complications

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appeared to reduce the feasibility of minimizing postsurgical astigmatism by manipulating a single running Mersilene suture (Table IV). Four of the six astigmatic failures had significant suture-related complications (two broken sutures, one early removal with wound dehiscence, one cheesewiring). The other two astigmatic failures did not have significant suture-related complications; however, one had no additional adjustment because maculopathy prohibited good corrected visual acuity. One eye had five suture adjustments with little reduction in corneal astigmatism. This patient had the first adjustment on postoperative day 73 compared to the mean of postoperative day 53. By risk-ratio analysis, patients with significant suture-related complications were 2.85 times more likely to have greater than 4 D of astigmatism than patients without suture complications. DISCUSSION MERSILENE SUTURE FOR PENETRATING KERATOPLASTY

In these two studies, Mersilene proved to be an unsuitable suture for penetrating keratoplasty because of its high incidence of complications. Study 1 demonstrated a statistically significant increased incidence of handling-related complications and a trend toward an increased incidence of tissue-related complications in Mersilene interrupted sutures compared to nylon. Study 2 demonstrated an unacceptable rate of complications when Mersilene was used as a single adjustable running suture. Interestingly, the high rate of complications seen in Study 2 was not apparent when Mersilene was used as a running suture in Study 1; perhaps the supporting role of the interrupted sutures prevented these complications from emerging. We think that two properties of Mersilene contributed to its high rate of complications: inelasticity and deformability. The loose exposed suture loops and the cheesewiring that we observed with Mersilene were complications on opposite extremes of the continuum of suture tension. As the early postoperative edema of the wound subsided, the inelastic Mersilene was unable to adapt to the new wound volume, and loops loosened, sometimes eroding through the epithelium. At the other extreme, in areas where the running Mersilene suture was under greater tension, especially after suture adjustment, its inelasticity overcame tissue resistance and the suture cheesewired through both the donor and the host. The stiff Mersilene suture is relatively deformable, and is easily crimped and flattened when it is grasped firmly with tying forceps. We think that

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this weakens the suture and leads to easier suture breakage. Suture breakage occurred in 3 of the 23 eyes (13%) in Study 2, whereas McNeil and Wessels'4 described no suture breakages out of 205 adjustments in their running nylon suture study using the same adjustment technique with the Tenant tying forceps. They did, however, break sutures when using a jeweler's forceps. Mersilene was also relatively difficult to handle during surgery. It tended to kink during placement and tying, and created knots that were more difficult to bury. Furthermore, Mersilene is dyed a light blue-green color and is more difficult to see under the operating microscope than the darker nylon. Mersilene suture has been used successfully to close limbal and scleral cataract wounds, with the purported advantage that its lack of elasticity and biodegradability will create a more stable wound with less astigmatism decay after surgery. Although Drews22 found no difference between nylon and Mersilene, Cravey23 demonstrated that Mersilene had less tendency to produce against the rule change in astigmatism after cataract surgery. ADJUSTMENT OF RUNNING SUTURES AFTER PENETRATING KERATOPLASTY

McNeil and Wessels14 reported 330 eyes that underwent penetrating keratoplasty with a single 10-0 nylon running suture; 205 of these underwent suture adjustment at the slit-lamp microscope under keratometric control. The mean keratometric astigmatism at least 6 months postoperatively with sutures in place was 3.23 D + 1.95 D. Fifty-five percent of eyes had less than 3.25 D of keratometric astigmatism. Van Meter and colleagues15 retrospectively compared combined running-interrupted nylon sutures with selective removal of the interrupteds to the adjustment of a single running suture. They reported a mean final astigmatism of 3.2 ± 1.9 D with the combined technique and 1.5 + 1.1 D with the single adjustable running technique with a median follow-up of 18 months. In addition, they found that the adjustable running technique required statistically fewer suture manipulations than the interrupted running technique. These investigators opened the corneal epitheliu'm 3600 at the graft host interface and dehisced Bowman's layer in the area of suture adiustment. Wood and Nabors16 have reported results of adjustment of a single running nylon suture with dehiscence of the stromal wound in the area of adjustment. The average preadjustment astigmatism was 10 D, which they were able to reduce an average of 8.1 D immediately, with a stable reduction of an average of 7.2 D 3 months following wound revision. Although we were able to reduce postoperative astigmatism with the

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adjustment of a single running Mersilene suture, the level of success was below that described by McNeil and Wesselsl4 and Van Meter et all' and worse than we achieved with a combined running-interrupted nylon technique.3'5 Our clinical impression was that the adjustment procedure, in the absence of significant suture complications, reduced postoperative astigmatism, but as the study progressed, the number of complications increased, reducing the frequency and extent of suture manipulation. Thus, two challenges currently confront the surgeon who wishes to actively adjust astigmatism after penetrating keratoplasty. The first is to perform prospective randomized clinical trials that compare combined running and interrupted sutures using selective removal of interrupted to adjustment of a single running suture with or without stromal wound dehiscence. The second challenge is to develop a biocompatible and clinically effective non-biodegradable suture that can be adjusted readily and then left in place permanently without complications. SUMMARY

Through two prospective studies, we evaluated the use of polyester (Mersilene) sutures in penetrating keratoplasty. Study 1 was a randomized comparison of combined running and interrupted Mersilene and nylon sutures (n = 45). Study 2 was a case series of single running Mersilene with postoperative adjustment of suture tension to manage astigmatism (n = 23). Study 1 demonstrated that Mersilene interrupted sutures were 5.5 times more likely to have handling-related complications compared to nylon (P = 0.01); in addition, they were 3 times as likely to have tissue-related complications as nylon interrupted sutures (P = 0.16). Study 2 demonstrated a complication rate of 69% when Mersilene was used as a single adjustable running suture. At 6 months postoperatively, the median refractive astigmatism for the adjustable cases was 3.37 D (mean, 4.03 ± 2.37 D). Eyes in Study 2 with significant suture-related complications were 2.85 times more likely to have greater than 4 D of refractive astigmatism than were eyes without suture-related complications. We concluded that Mersilene is an undesirable suture for use in penetrating keratoplasty. REFERENCES 1. Jensen AD, Maumenee AE: Refractive errors following keratoplasty. Trans Am Ophthalmol Soc 1974; 72:123-131. 2. Troutman RC, Kelly S, Kaye D, et al: The use and preliminary results of the Troutman surgical keratometer in cataract and corneal surgery. Trans Am Acad Ophthalmol Otolaryngol 1977; 83:232-238.

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3. Pradera I, Ibrahim 0, Waring GO: Refractive results of successful penetrating keratoplasty, intraocular lens implantation with selective suture removal. Refract Corneal Surg 1989; 5:231-239. 4. Binder PS: The effect of suture removal on postkeratoplasty astigmatism. AmJ Ophthalmol 1988; 104:637-645. 5. Burk LL, Waring GO, Radjee B, et al: The effect of selective suture removal on astigmatism following penetrating keratoplasty. Ophthalmic Surg 1988; 19:849-854. 6. Harris DJ, Waring GO, Burk LL: Keratography as a guide to selective suture removal for the reduction of astigmatism after penetrating keratoplasty. Ophthalmology 1989; 96: 1597-1607.

7. Cottingham AJ: Residual astigmatism following keratoplasty. Ophthalmology 1980; 87:113. 8. Stainer GA, Perl T, Binder PS: Controlled astigmatism of postkeratoplasty astigmatism. Ophthalmology 1982; 89:668-676. 9. Binder PS: Selective suture removal can reduce postkeratoplasty astigmatism. Ophthalmology 1985; 92:1412-1416. 10. Feldman ST, Brown SI: Reduction of astigmatism after keratoplasty. Am J Ophthalmol 1987; 103:477-478. 11. Burk LL, Radjee B, Stulting RD, et al: Changes in astigmatism after removal of individual sutures in penetrating keratoplasty. Invest Ophthalmol Vis Sci (Suppl) 1986; 27:92. 12. Kozarsky AM, Waring GO: Photokeratoscopy in the management of astigmatism following keratoplasty. Dev Ophthalnmol 1985; 11:91-98. 13. McNeil JI, Kaufman HE: A double running suture technique for keratoplasty: Earlier visual rehabilitation. Ophthalmic Surg 1977; 8:58-61. 14. McNeil JI, Wessels IF: Adjustment of single continuous suture to control astigmatism after penetrating keratoplasty. Refract Corneal Surg 1989; 5:216-223. 15. Van Meter WS, Gussler JR, Steineman TL, et al: Control of astigmatism following keratoplasty with an adjusted single continuous suture compared to combined running interrupted suturing. Invest Ophthalnmol Vis Sci (Suppl) 1990; 31:1483. 16. Wood TO, Nabors G: Wound revision for post-keratoplasty astigmatism. Invest Ophthalmol Vis Sci (SUPPl) 1990; 31:2815. 17. Mader TH, Yuan R, Lynn MJ, et al: Changes in keratometric astigmatism following suture removal more than one year after penetrating keratoplasty. Invest Ophthalmol Vis Sci (Suppl) 1990; 31:2811. 18. Musch DC, Meyer RF, Sugar A: The effect of removing running sutures on astigmatism after penetrating keratoplasty. Arch Ophthalmol 1988; 106:488-492. 19. Waring GO, Hanna KD: The Hanna suction punch block and trephine system for penetrating keratoplasty. Arch Ophthalmol 1989; 107:1536-1539. 20. van Rij G, Waring GO: Configuration of corneal trephine opening using five different trephines in human donor eyes. Arch Ophthalnmol 1988; 106:1228-1233. 21. Kenyon KR, Grene RB: The anchor suture for securing loosened, continuous sutures in penetrating keratoplasty. Refract Corneal Surg 1989; 5:268-270. 22. Drews RC: Astigmatism shift after extracapsular surgery: Mersilene vs nylon. Int Ophthalmol 1989; 13:209-210. 23. Cravey TV: Long term corneal astigmatism related to selected elastic, monofilament, and non-absorbable sutures. J Cataract Refract Surg 1989; 15:61-69.

DISCUSSION

DR RICHARD D. RiCHARDS. I thank the authors for providing a copy of the paper sufficiently in advance to permit me to prepare a discussion. I also congratulate the authors on the clear presentation. Doctor Waring is well known for his ability

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to communicate effectively, and he has done that this morning. His study was designed to determine the effectiveness of adjustment of a running Mersilene suture, after penetrating keratoplasty, in reducing the astigmatic error and thereby improving the vision in the immediate postoperative period. The desired result was to obtain earlier rehabilitation in patients after corneal transplantation. In designing his study, Doctor Waring asked two questions. First, "What is the general behavior of running Mersilene suture in penetrating keratoplasty?" Mersilene suture is inelastic, and the study showed it was easily damaged by postoperative marnipulation. The number of complications was significant, including suture breakage, cheesewiring of the sutures, and frequent extensive loosening which required early removal of many sutures. However, I would like to ask him if these complications were reduced in number and severity as he gained experience using the Mersilene, and therefore could these deficiencies be overcome so that the original premise of using a nonelastic suture is worth considering? Second, "What is the efficacy of postoperative adjustment of running Mersilene in managing postoperative astigmatism?" His series consisted of 23 patients, with 11 grafts done with 10-0 suture, and 12 grafts done with 11-0 suture. His goal was to reduce the refractive astigmatism to less than or equal to 3.25 D. Sixty-eight percent of his patients were regarded as failures, only 18% as successes, and 14% were intermediate at 3 months. At 6 months, 50% were astigmatic successes, 27% failures, and 23% intermediate. Four of the six failures had significant suturerelated complications. The conclusion was that Mersilene sutures were not effective in controlling astigmatism when used as a single running adjustable suture. There were no controls for comparison. These results were certainly not as good as those achieved by McNeil, with a considerably larger group of 330 eyes using a running 10-0 nylon suture and using suture "adjustment" at the slit-lamp with keratometric control. I would like to ask the authors if there was any difference between 10-0 and 11-0 suture in rate of complication, or astigmatic success rate. The number of patients is too small to permit any statistical evaluation. It is refreshing to hear a report that so clearly lists the significant complications that occurred in the study, so that we can avoid duplicating them. This study clearly identifies the problems associated with a running adjustable Mersilene suture after penetrating keratoplasty. I congratulate Doctor Waring and his group on bringing this information to us in such a clear and well presented fashion. DR DANIEL M. TAYLOR. I enjoyed Doctor Waring's paper very much and I am pleased that he is a new member of this organization. In my opinion, he will contribute significantly to future meetings. Just a few words about astigmatism in general. All of us who perform keratoplasty have had to grapple with this problem throughout most of our careers. My own experience with keratoplasty goes back 39 years, and I have certainly had my share of astigmatism. I concluded some time ago that postkeratoplasty astigmatism is at least 50% to 60% surgeon-induced and perhaps only 40% due to

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irregular wound healing. This slide demonstrates a point that I believe will be apparent even to members sitting in the rear of the room. You will see two corneal buttons each removed from an eye bank eye, with an 8 mm trephine. The button on the left was removed by external trephination, and the button on the right was removed by punch technique, endothelial side up, on a concave block. The externally trephinated button is obviously grossly larger than the internally punched button, yet the trephine was the same size. I believe that even an untrained observer would be aware of the size discrepancy, just as it is apparent that a nickel has a greater diameter than a dime. The next slide shows the graft host disparity between the externally trephinated recipient eye and the punched donor button. The donor button is too small and simply does not fit. We were unaware of this simple fact in the early 1970s when we first began to punch donor buttons from corneas preserved in media. There is simply no way of suturing in this relatively small button without producing significant astigmatism, which most of us did achieve during the early 1970s. The problem was solved by the simple realization that we had to use a trephine 2/10 to 1/2 mm greater in diameter on the punched donor button than the one used for the recipient eye. With this simple change in technique, graft host size disparity was eliminated and, along with it, a reduction in postoperative astigmatism. The second cause for astigmatism is errors in operative technique during trephination. If we are not exactly perpendicular with the placement of our handheld trephines, the trephination will result in an elliptical bed to house our round punched donor button. This will, of course, result in significant astigmatism regardless of our best efforts at wound closure. This problem has been partially solvd by the use of modern trephines that are attached directly to the cornea during the trephination process, such as the Hessburg trephine and Krumeich trephine. Another factor that has led to considerable astigmatism in the past has been faulty suturing technique. Without wishing to trivialize this, we are simply sewing little buttons into little holes, but we must be very careful in placing these sutures as accurately as possible. We are all capable of inducing enormous amounts of astigmatism simply by not accurately aligning our initial cardinal sutures. If these initial four sutures are malplaced, all additional sutures, whether running or interrupted, will simply tightly hold the graft in its malposition, thus producing the unwanted astigmatism. I cannot emphasize enough the importance of accurately aligning the initial four cardinal sutures. In addition, over-tightening the sutures can result in significant astigmatism. Finally, we have the problem of surgical inexperience. We have surgeons in this country who do only 1 to 2 keratoplasties a year, and without considerable luck, it would be virtually impossible for them to really be able to handle the astigmatic

problem. In addition to the surgeon-induced reasons for postkeratoplasty astigmatism, we have the remaining 40% of patients who develop astigmatism through some anomaly in wound healing. Sutures placed in boggy, edematous corneas may have

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a tendency to cheese-wire, thus resulting in irregular support before firm healing can occur. Differences in thickness of the host cornea, due to scarring or other pathology, resulting in disparity between the thickness of the graft and the recipient in one or multiple areas, can also lead to astigmatism. Corneal melting can occur at the graft host junction in patients with rheumatoid arthritis or dry eyes, resulting in tilting of the graft and considerable astigmatism. Thus, the existence of the original corneal pathology can result in irregular scar formation that will undermine our best technical efforts. A few years ago, I became interested in the problem of postkeratoplasty astigmatism because the subject was being widely discussed at our various meetings and papers were being published. The large degrees of astigmatism of 15 d or more being reported were practically nonexistent in my own experience of almost four decades. In order to make a quick assessment of what we were achieving, in September of 1988, I simply took the first 50 cases of postkeratoplasty patients who appeared for routine refractions that had received their keratoplasties between 1983 and 1986. All of these patients had received double running 10-0 and 11-0 nylon antitoxics, and all sutures had been removed at the end of the first year. None of these 50 patients received a suture adjustment. This slide shows the distribution of cases which is quite representative of any standard keratoplasty series. There were 11 keratoconus patients, 13 pseudophakic bullous keratopathy patients, 4 aphakic bullous keratopathy patients, 10 Fuchs' dystrophy patients, 5 interstitial keratitis patients, 1 herpetic keratitis patient, 1 corneal leukoma, and 1 acute corneal ulcer. Without the benefit of suture adjustment, we found that our average astigmatism in this series was 2.51 D. Seventy percent of the patients fell between 0 and 3 D, and 95% were between 0 and 4 D. Overall, I would state, that about 95% of the time, our graft patients are left with clinically acceptable levels of astigmatism that have not required any type of intervention. About 5% of the time, we are left with over 5 to 6 D of astigmatism, rarely exceeding 7.5 D and, in these patients, some type of astigmatic surgery is required. For every series of 100 grafts, we would therefore have to perform relaxing incisions or T-cuts with compression sutures in approximately 5 cases. It must be remembered that the adjustment of postkeratoplasty sutures does carry some degree of morbidity, and I myself have had two instances of endophthalmitis in earlier years with interrupted suture removal as far as 9 months postoperatively. I believe that the results that we have presented here compare favorably with the results of those who have meticulously adjusted sutures, beginning 6 weeks postoperative. Again, my congratulations to Doctor Waring for an excellent presentation. DR RICHARD TROUTMAN. Doctor Waring, as usual, has presented a very thoughtful and provocative paper. As he and I are painfully aware, searching for a cause or a preventive treatment for astigmatism after penetrating keratoplasty is akin to Sir Richard looking for the Holy Grail. Another problem we have encountered with Mersilene, in addition to break-

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age, is a sterile infiltrate forming along the external thread loop postoperatively necessitating early removal which can be a particular problem with a continuous suture. Why do you feel it is necessary to wait for up to 3 to 5 years to have a stable cornea in keratoconus? We remove all sutures in 6 months and by 1 year in other patients with softer corneas which heal less rapidly. These corneas are optically stable and can be treated successfully with secondary corrective procedures within 3 months following suture removal. The cause of astigmatism is multifactorial, as Doctor Taylor has pointed out. Since we cannot readily identify a single cause we are currently limited to treat the symptoms only with sutures or by secondary correction. As a step to prevention we have been using for the past 3 years several types of suction trephines. I would like to ask Doctor Waring if he used the Hanna trephine, which he has been evaluating, in this series since he has shown it to cut a more regular recipient opening. We have been evaluating the Krumeich trephine which cuts accurately not only the recipient but also the donor at an 8 mm diameter. The more accurate match and fit obtained has reduced our residual "sutures out" astigmatism by 50% in a series of keratoconic corneas, as we reported at ARVO this month. I described the deleterious effects of donor mismatch first in 1976 at the Corneal Congress in Washington. At that time we didn't have trephines graduated in 0.25 or 0.5 mm diameters. We had only the Franceschetti trephine which was 0.1 larger in diameter than the recipient trephine. This gave us a better fit when the donor was cut with the larger diameter trephine using the Amsler punch technique leading us to advise the disparate diameter graft recipient technique. DR THOMAS 0. WOOD. Although I appreciate Doctor Troutman's remarks about being able to cure postkeratoplasty astigmatism before we cause it, at present it remains a major postoperative problem. Doctor McNeill has been doing this procedure for approximately 8 years. He showed us, that by adjusting a single running 10-0 nylon suture, he would reduce astigmatism; he also demonstrated that when the sutures were removed there was no significant increase in the astigmatism. We have used McNeill's suture adjustment technique for 2 years; our results will be reported tomorrow. I'm curious, because I am guilty of this and I think a lot of surgeons are I read about a technique that someone has been doing for 6 years as Doctor McNeill, and my conclusion is, he has a good idea but he is doing it wrong. So I am going to start my learning curve doing it completely different. In this case, instead of using nylon, the suture Doctor Waring used to learn the technique was polyester, and it didn't work. Doctor Waring, maybe you can tell me, what makes us do this? DR GEORGE 0. WARING. Doctor Richards, thank you for your kind comments. We identified no difference between the 10-0 and 11-0 suture behavior. Neither one of them worked very well. You asked whether we could learn to work with Mersilene

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if we got more experience. The answer is no. The problems that we had are not really surgeon-related, they are inherent properties of the inelastic suture that can't adapt itself to changing wound volume from edema and wound contraction. Nylon is like tires on a rough road; it conforms to the situation, but Mersilene just sits there and loosens up. Doctor Wood asks the question, "Why on earth try Mersilene? Why didn't we just use nylon?" The answer is because there is a need for a nonbiodegradable suture if we're going to try to set the cornea in a particular shape and leave it there for a long time. Doctors Taylor and Troutman may say, "Just take the sutures out early and if astigmatism results, just fix it. " But I'm unwilling to wait 12 months in my corneal edema and keratoconus cases and say, "Well, I know you can't see well for a year or so, but we'll take care of this next year." I don't think this is acceptable in the modern world, when we can adjust the sutures and get patients seeing pretty well at 3 months. The questions that Doctor Taylor raised about how the wound and the sutures cause astigmatism could occupy the rest of this meeting. I think the time is coming when a new generation of corneal trephines will be used and when we'll put our manual trephines in the AOS history collection. Why? Because everyone who has tried to take a manual trephine and hold it perpendicular to the tangent of the surface of the cornea knows that it is impossible to make perfectly smooth cuts. And as Doctor Taylor mentioned, we cut the button out with scissors, leave a little bevel, go back and trim the wound, undercut one place and overcut another. We now have suction trephines-the Hanna trephine marked by Moria in Paris and the Krumeich trephine that use suction rings around the limbus to hold the trephine perpendicular to the cornea; if the eye moves, the trephine is always perpendicular. They can cut all the way through without undercutting. And these two trephines are more expensive and are a little bit trickier to use, but they make much better wounds. Whether that will reduce astigmatism remains to be proven. The shape of the button and host wounds may not be the solution to astigmatism. I don't think round or oval buttons are the most important thing. Doctor Cohen has shown that the wound volumes determines astigmatism. If you've got a wide wound at 12 o'clock and a narrow wound at 9 o'clock, you're more likely to get astigmatism. Doctor Troutman has been advocating full thickness sutures for years because of that. He's always said, "You've got to get Descemet's apposed to Descemet's, Bowman's to Bowman's." I think that this is the important thing. We really haven't learned to do that reliably. Finally, we have a prospective randomized trial underway at Emory now comparing a single running suture adjustment vs selective removal of interrupted sutures. Maybe next year at this meeting we can tell you which of these techniques we think is better.

Inadequacy of a polyester (Mersilene) suture for the reduction of astigmatism after penetrating keratoplasty.

Through two prospective studies, we evaluated the use of polyester (Mersilene) sutures in penetrating keratoplasty. Study 1 was a randomized compariso...
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