Different suturing techniques variously affect the regularity of postkeratoplasty astigmatism

Different Suturing Techniques Variously Affect the Regularity of Postkeratoplasty Astigmatism Massimo Busin, MD,’

Thomas M&&s,

MD,2 lbrahim Al-Nawaiseh,

MD3

Objective: This study aimed to determine the effect of various suturing techniques on the regularity of postkeratoplasty astigmatism. Design: A prospective clinical trial. Participants: Sixty-two consecutive patients undergoing penetrating keratoplasty by the same surgeon (MB) participated. Intervention: Each patient was assigned to one of four groups according to the suturing technique used (a = 16 interrupted 10-O nylon sutures; b = 2 running 10-O nylon sutures, each with 8 bites; c = 2 running 10-O nylon sutures, each with 12 bites; d = 2 running 10-O nylon sutures, each with 16 bites). This was the only parameter permitted to be changed in the standard keratoplasty procedure used for all cases. Cornea1 topography was performed 1, 3, and 6 months after surgery. The astigmatic patterns seen on the cornea1 maps then were classified into regular (symmetric or asymmetric bowtie patterns) or irregular (distorted bowtie, multiaxial, or other patterns). Main Outcome Measures: Regularity of postkeratoplasty cornea1 astigmatism was measured. Results: At all postoperative examination times, the percentage of irregular astigmatic patterns was highest in group a and lowest in group d (chi-square test: P < 0.005). Groups b and c showed intermediate values. The entity of the astigmatic error as measured by the simulated K-readings of the topographic maps did not differ significantly in the four groups. Conclusions: A suturing technique using 2 running sutures with 16 bites each can minimize irregular postkeratoplasty astigmatism as long as sutures are in place, when compared with interrupted sutures or double-running sutures of less than 16 bites. Ophthalmology 7998; 705:1200- 7205

High-degree astigmatism has been shown to complicate the postoperative course of penetrating keratoplasty (PK) in a relatively high percentage of cases.le8 Even with the use of optical devices (spectacles or contact lenses), these patients often experience poor vision despite the presence of a perfectly clear graft. The degree of their functional impairment is related not only to the amount of astigmatic error, but also to its regularity. Conventional keratometry can quantify postkeratoplasty astigmatism only in corneas with regular morphology. More recently, computer-assisted cornea1 topography has been shown to enable measurement of the refractive power of almost the entire corneal surface as well as to simulate the measurement of conventional keratometry readings (so-called “Sim-K readings”),‘-” even in the presence of irregular astigmatism. To date, several authors have investigated the influ-

ence of various suturing techniques on postkeratoplasty astigmatism,2.6,7 but only recently have Sim-K or surface asymmetry index values been used in relatively small series to address the evaluation of the resulting astigmatic errors.‘2-14 In the current study, we prospectively evaluated, by means of computer-assisted cornea1 topography, the effect of 4 different suturing techniques on the postoperative astigmatism of 62 consecutive patients who underwent standard PK by the same surgeon (MB). In an attempt to simplify the evaluation of postkeratoplasty astigmatism and the influence that different variables (e.g., suturing technique) may have on it, the cornea1 maps obtained were classified according to their morphologic characteristics, allowing a “first-glance analysis” of cornea1 regularity.

Originally received: February 5, 1997. Revision accepted: September 15, 1997. ’ Umversity of Bonn, Bonn, Germany. ’ Private practice, Krefeld, Germany. ’ University Eye Hospital, Amman, Jordan. Presented as a poster at the Annual Meeting of the American Academy of Ophthalmology, Chicago, Illinois, October 1996. Address correspondence and reprint requests to Masslmo Busin, MD, Burgstr. 6 I, 545 I6 Wittlich, Germany.

Materials

1200

and Methods

All patients undergoing PK surgery by the same surgeon (MB) from January 1994 to March 1995 were included in this prospective study. The surgical procedure used included, in all cases, (I) the use of a McNeill-Goldman ring for the fixation of the globe; (2) the trephination of an 8.0-mm button from the endothelial side of the donor cornea by means of a Barron suction punch; and (3) the trephination of a 7.5recipient bed

Bush et

al * Suturing

Techniques

Figure 1. Suturmg

technques used in the current study. A, 16 mterrupted 12 bttes each; and D, 2 runnmg sutures with 16 bites each.

using a Barron suction trephine. The performance of additional procedures (e.g., cataract or intraocular lens surgery or both) was possible without affecting the standard PK technique. Each patient was assigned to one of four different suturing techniques (Fig I): a = 16 interrupted 10-O nylon sutures; b = 2 running 10-O nylon sutures, each with 8 bites; c = 2 running 10-O nylon sutures, each with 12 bites; d = 2 running 10-O nylon sutures, each with 16 bites. There were five patients with vascularized corneas who were assigned to group a. Cornea1 topography was analyzed I, 3, and 6 months after surgery by means of the Topography Modeling System (Tomey, New York, NY). The maps obtained were classified according to their morphologic characteristics (i.e., astigmatic pattern) into five groups: (I) symmetric bowtie (two hemiaxes of the same size and on the same meridian); (II) asymmetric bowtie (two hemiaxes of different size but on the same meridian); (III) distorted bowtie (two hemiaxes of the same or different size on different meridians); (IV) multiaxial (more than two hemiaxes); and (V) no pattern detectable. Figure 2 shows examples of each of the five groups. Attempts made to obtain reliable K-readings with conventional keratometry showed that this was possible only for the corneas of groups I and II. The astigmatic patterns of these two groups were therefore considered regular, and those of groups III, IV, and V were considered irregular. The distribution of regular and irregular astigmatic patterns for each suturing technique used was recorded at each examination time, and a chi-square test was used to analyze these results statistically. In addition, the absolute value of the astigmatic error, as measured by the difference between the two Sim-K readings on the topographic maps, was recorded for each patient at each examination time. A chi-square test was used to compare the average values

and Postkeratoplasty

sutures;

B, 2 running

Astigmatism

sutures with 8 bites each; C, 2 running

suture5 with

(*standard deviation) obtained from regular astigmatic patterns with those obtained from irregular astigmatic patterns at the different examination times.

Results At the time of this review, 62 consecutive patients (males = 31, females = 3 1) undergoing PK surgery had a minimum follow-up of 6 months. No cornea1 decompensation was seen, nor were other complications recorded that could have affected the performance of computer-assisted cornea1 topography. The average age at the time of surgery was 58.7 -t 19.4 years (range = 15-85 years). The indications for surgery are listed in Table 1. Table 2 summarizes all other surgical procedures performed in association with PK surgery, whereas Table 3 lists the number of patients assigned to each type of suturing technique at the time of this review. The percentage of regular astigmatic patterns recorded in group d was significantly higher (P < 0.005) than that recorded in the other groups at all examination times, whereas the pattern distribution of groups b and c did not differ significantly from that of group a (Table 4). However, when compared with group a, a tendency toward a higher number of regular astigmatic patterns could be seen in group b and even more in group c. Regarding the time of examination, no substantial differences in the proportion between regular and irregular patterns could be seen over time in any of the four groups. Figure 3 summarizes the results obtained to date in our study. As far as the astigmatic error measured by means of Sim-K readings was concerned, no significant differences among the

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Busin et al * Suturing Table 1. Indications for Penetrating

Techniques

Keratoplasty Surgery

Aphaklc or pseudophaktc bullous keratopathy Keratoconus Cornea1 degeneration (s/p interstitial keratitls) Cornea1 dystrophy Cornea1 scar (s/p trauma) Others

16 11 10 11 6 8

Total

62

s/p = status post.

four groups could be detected at any postoperative examination time. Table 5 lists the average values (kstandard deviation) as well as the range of astigmatism recorded in our study for each suturing technique group at each postoperative examination time.

Discussion Astigmatism impairing postkeratoplasty visual acuity has been reported to occur in a relatively high number of patients. ’ -* Among the many surgical variables held responsible for the wide range of astigmatic errors seen after PK, suturing techniques have been investigated by various authors over the past years.2~7~‘2-‘9 These studies mainly focused their attention on the amount of astigmatism induced by different suturing materials and patterns as well ason the stability of the astigmatic error, in particular before and after suture removal. However, in most cases, the technique used to quantify postkeratoplasty astigmatism was conventional keratometry, which gives punctual, accurate measurementsonly if the cornea1curvature is regular. In the presenceof irregular astigmatism, as often seen after PK surgery, an important source of error was therefore included in the evaluation of the results. The relatively recent development of computer-assisted cornea1 topography”-” has allowed the quantification of the curvature of almost the entire cornea1surface independently on the characteristics of its shape. On the cornea1mapselaborated by the computer, the distribution of areaswith different dioptric power both quantifies the amount of astigmatism eventually present over almost the entire cornea1surface and allows visualization of its

2. Procedures

Table

3. Distribution

Astigmatism of Patients

According

Techniyue

Used

to the Suturing

No. of Patients

Indication

Table

and Postkeratoplasty

Performed No. of

Type of Procedure

Patients

Penetratmg keratoplasty Penctratmg keratoplasty, extracapsular cataract extractIon, and mtraocLdar lens implantation Penetratmg keratoplasty and intraocular lens exchange Repeat keratoplasty

32

Total

62

18 6 6

Suturing Technique

No. of Patients

16 interrupted 10-O nylon sutures Double running 10-O nylon xmlre with 8 bites each Double runnmg lOsO nylon suture with 12 bites each Double runnmg IO-O nylon suture with 16 bites each

15 13 22 12

morphologic characteristics. In addition, the researchers have developed a Sim-K reading index, which correspondsto the value obtained with conventional keratometry. Thus, irregular postkeratoplasty astigmatic errors that could not be measured by conventional keratometry can be evaluated objectively by cornea1topography. Our study showed that up to 6 months after surgery, irregular astigmatic errors are induced by PK surgery in a proportion variable according to the different types of suturing technique used. In particular, a double-running 10-O nylon suture with 16 bites induced irregular astigmatism in a significantly lower number of patients than 16 interrupted 10-O nylon sutures did, whereas Sim-K readings did not differ significantly between the 2 groups. An investigator using only conventional keratometry probably would have failed to show any significant difference in terms of postkeratoplasty astigmatism, thus underscoring the impossibility of properly correcting the irregular refractive error of many patients. Other authors’5,2” using a double-running suturing technique have indeed shown values of postkeratoplasty keratometric astigmatism similar to those recorded in our study, but no information was given in these publications concerning the astigmatism regularity. In addition, the double-running technique used by these authors (one 10-O nylon and one 11-O nylon suture, both with 12- 16 bites) differed substantially from that used in our study (two 10-O nylon sutures, both with 8, 12, or 16 bites). A possible explanation for our result is that increasing the number of total bites to 32 (twice 16 bites) allows the surgeonto close the surgical wound with minimal tension in the suture, thus reducing cornea1distortion and irregular astigmatism. Selecting the double-running 10-O nylon suturing technique, the surgeon could offer the advantage of correcting the postkeratoplasty refractive error properly also for the time when sutures are in place, which usually is

Table 4. Significance (P) of the Difference in the Percentage of Regular Astigmauc Patterns Recorded in rhe Four Groups of Patients at Each Postoperative Examination Time

(Chi-square

Group Group Group

a versus group b a versus group c a versus group d

Test)

1 mo

3 mm

Postoperation

Postoperation

6 mos Postoperation

<0.05 <0.05 >o.oos

10.05 ‘co.05 >o.oos

<0.05 <0.05 >0.005

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[3reguklr

Oregular

I Clirregular

I ellrregular

a

b

II

I

Oregular

Oregular Chrregular

tAirregular

cl

7

Figure 3. Dutrlbutmn of regular and irregular astlgmatlc patterns m each of the four groups dt each exammatlon ume. Group a = 16 Interrupted sutures; group b = 2 runnmg sutures with 8 bites each; group c = 2 runnmg sutures wth 12 bites each, and group d = 2 runnmg sutures wth 16 bites each

up to 1 year. In addition, the surgeon could elect to perform suture removal 1 year after surgery only in that minority of patients with irregular astigmatism rather than continue to follow-up the rest, even for a considerably longer period of time. Another aspect shown by our re-

Table 5. Average Astigmatism” Each Postoperarive Exammation: 1 mo

Postoperation 0) 16 Interrupted sutures 2X8 2 x 12 2 x 16

5.26 !I 3.12 (3.25-11.50) 4.23 k 3.81 (3.75-9.75) 4.82 t- 3.36 (2.25-11.50) 4.71 t 2.98 (2.50-9.00)

* Ranges are in parentheses.

1204

Recorded in Each Group at Mean c Standard Deviation 3 mos Postoperation (D)

6 mos Postoperation 6))

5.1 2 2.73 (3.25-11.00) 4.56 + 3.55 (3.75-10.75)

4.89 2 3.16 (4.00-11.00) 4.42 2 3.38 (3.00-10.00) 3.98 + 3.69 (2 25-10.00) 3.62 5 2.21 (2 50-9.50)

4.14 2 3.11 (2.75-9.75) 4.3 + 2.56 (2.50-9.50)

searchwas that the proportion between regular and irregular patterns remained substantially stable over a postoperative period of 6 months (Fig 2), no matter which suturing technique had been used. This suggeststhat the cornea1 shape obtained early after PK surgery does not undergo major changes as long as sutures are in place. In conclusion, the use of computerized cornea1topography can be recommended to optimize the evaluation of postkeratoplasty errors induced by different suturing techniques. Our study suggeststhat a double-running lo0 nylon suture with 16 bites should be preferred when performing a double-running suture technique to minimize irregular postkeratoplasty astigmatism early after surgery.

References 1. De Molfetta

V, Brambilla

M, De Casa N, et al. Residual

cornea1astigmatismafter perforatingkeratoplasty.Ophthalmologica

1980; 179:316-21.

2. Binder PS.Controlledreductionof post-keratoplastyastigmatism. In: Brightbill FS, ed. Cornea1Surgery: Theory,

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Technique, and Tissue. St. Louis: The C.V. Mosby Company, 1986; 326-32. Price NC, Steele AD. The correction of post-keratoplasty astigmatism. Eye 1987; I :562-6. Sayegh FN, Ehlers N, Farah I. Evaluation of penetrating keratoplasty in keratoconus. Nine years follow-up. Acta Ophthalmol (Copenh) 1988;66:400-3. de Charnace B, Guidi M, Valiere-Vialeix JP. Complications post-operatoires a court, moyen et long terme sur 150 keratoplasties transfixiantes ayant au moins 1 an de recul [Eng abstract]. Ophthalmologie 1989; 3: 11-2. Hope-Ross MW, McDonnell PJ, Corridan PG, et al. The management of post-keratoplasty astigmatism by post-operative adjustment of a single continuous suture. Eye 1993; 7:625-g. Murta JN, Amaro L, Tavares C, Mira JB. Astigmatism after penetrating keratoplasty. Role of the suture technique. Dot Ophthalmol 1994; 87:331-6. Williams KA, Muehlberg SM, Lewis RF, Coster DJ. How successful is cornea1 transplantation? A report from the Australian Cornea1 Graft Register. Eye 1995;9:219-27. Dingeldein SA, Klyce SD, Wilson SE. Quantitative descriptors of cornea1 shape derived from computer-assisted analysis of photokeratographs. Refract Cornea1 Surg 1989;5: 372-8. Wilson SE, Klyce SD. Quantitative descriptors of cornea1 topography. A clinical study. Arch Ophthalmol 1991; 109:349-53. Wilson SE, Klyce SD. Advances in the analysis of cornea1 topography. Surv Ophthalmol 1991;35:269-77. Lin DTC, Wilson SE, Reidy JJ, et al. An adjustable single running suture technique to reduce postkeratoplasty astig-

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19. 20.

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matism. A preliminary report. Ophthalmology 1990;97: 934-8. Khong AM, Mannis MJ, Plotnik RD, Johnson CA. Computerized topographic analysis of the healing graft after penetrating keratoplasty for keratoconus. Am J Ophthalmol 1993; 115:209-15. Serdarevic ON, Renard GJ, Pouliquen Y. Randomized clinical trial of penetrating keratoplasty. Before and after suture removal comparison of intraoperative and postoperative suture adjustment. Ophthalmology 1995; 102:1497-503. Musch DC, Meyer RF, Sugar A, Soong HK. Cornea1 astigmatism after penetrating keratoplasty. The role of suture technique. Ophthalmology 1989;96:698-703. Van Meter WS, Gussler JR, Soloman KD, Wood TO. Postkeratoplasty astigmatism control. Single continuous suture adjustment versus selective interrupted suture removal [published erratum appears in Ophthalmology 199 1; 98:1005-71. Ophthalmology 1991;98:177-83. Mader TH, Yuan R, Lynn MJ, et al. Changes in keratometric astigmatism after suture removal more than one year after penetrating keratoplasty. Ophthalmology 1993; 100:119-26. Serdarevic ON, Renard GJ, Pouliquen Y. Randomized clinical trial comparing astigmatism and visual rehabilitation after penetrating keratoplasty with and without intraoperative suture adjustment. Ophthalmology 1994; 101:990-9. Filatov V, Steinert RF, Talamo JH. Postkeratoplasty astigmatism with single running suture or interrupted sutures. Am J Ophthalmol 1993; 115:715-21. Assil KK, Zarnegar SR, Schanzlin DJ. Visual outcome after penetrating keratoplasty with double continuous or combined interrupted and continuous suture wound closure. Am J Ophthalmol 1992;114:63-71.

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