|Year : 1997 | Volume
| Issue : 1 | Page : 37-41
Releasable suture technique for trabeculectomy
R Thomas, P Jacob, A Braganza, A Mermoud, J Muliyil
Schell Eye Hospital, Christian Medical College, Vellore, India
Schell Eye Hospital, Christian Medical College, Vellore
A retrospective review of 154 trabeculectomies with releasable sutures was performed to assess the effect of suture release on intraocular pressure (IOP) at various postoperative periods. Release of the suture was necessary in 38% of cases. The immediate reduction in IOP was significant (p <0.01) when the suture was released during the first three postoperative weeks. Seventy percent of eyes had a reduction in IOP more than 5 mmHg if released within the first week compared to 20% after the third week. With suture release after the third postoperative week, there was no clinically significant decrease in IOP. The decrease in IOP was similar in eyes undergoing trabeculectomy alone or when cataract extraction through a separate corneal incision was undertaken simultaneously. The period during which release of suture was effective was not prolonged by use of antimetabolites. Complications included a typical windshield-wiper keratopathy (18 eyes), failure to release the suture (13 eyes), epithelial abrasion (6 eyes) and a sub-conjunctival bleed (1 eye).
Keywords: Trabeculectomy, Releasable suture, 5-Fluorouracil, Mitomycin-C
|How to cite this article:|
Thomas R, Jacob P, Braganza A, Mermoud A, Muliyil J. Releasable suture technique for trabeculectomy. Indian J Ophthalmol 1997;45:37-41
|How to cite this URL:|
Thomas R, Jacob P, Braganza A, Mermoud A, Muliyil J. Releasable suture technique for trabeculectomy. Indian J Ophthalmol [serial online] 1997 [cited 2014 Aug 21];45:37-41. Available from: http://www.ijo.in/text.asp?1997/45/1/37/15026
To decrease the complications of early postoperative over-filtration after trabeculectomy, a tightly sutured scleral flap is widely recommended.Titration of filtration in the postoperative period is currently attempted with digital massage,, laser suturolysis or a releasable suture technique. Laser suturolysis is generally done within two weeks after trabeculectomy and successfully reduces IOP by enhancing filtration., Laser suturolysis, though effective, requires access to an argon laser and a Hoskin's or equivalent lens which enables compression of the filtration area during the procedure. These and other disadvantages have led to the use of releasable suture techniques.
The pressure lowering effect of suture release as a function of time after surgery has not been adequately reported. We evaluated this effect in 154 consecutive trabeculectomies with and without cataract extraction. Further, we studied whether antimetabolite therapy extended the period in which suture release was clinically effective in reducing IOP.
| Materials and methods|| |
The records of all patients undergoing primary trabeculectomy with releasable suture technique with or without cataract extraction from January to December 1992 were reviewed.
A fornix based conjunctival flap was used for all cases and trabeculectomy was performed using the technique described by Cairns. In no case was a tenonectomy performed. In 14 eyes daily sub-conjunctival injections of 5 mg of 5-fluorouracil (5-FU) were given postoperatively 180° away from the trabeculectomy site for 5 to 7 days (mean dose 30 mg). In another 54 eyes 0.4 mg/ml mitomycin C was applied intraoperatively for three minutes under the conjunctiva before dissecting the scleral flap. The antimetabolites were used with primary surgery, the most common indication being poor socio-economic status with demonstrable noncompliance with medications and anticipated problems with follow-up. None of the eyes which had antimetabolites were re-operations. The releasable suture technique used was a modification of the method described by Cohen. Following excision of the trabeculectomy block the corners of the rectangular scleral flap were sutured down and a releasable suture was applied halfway along one vertical edge of the flap. A 10-0 monofilament nylon suture on a spatulated needle was passed intrastromally through the cornea, onto the scleral flap, and looped out. The scleral flap suture was then passed. The suture end "a" was tied to the loop "b" with four throws to form a slip knot [Figure - 1]. The corneal end was trimmed to 3 mm. This technique was not varied between cases. Postoperatively, to effect release, the corneal end was grasped with a pair of forceps and pulled gently.
Seven surgeons in all performed the operations. The level of experience of the surgeons varied from third year residents to senior consultants. All followed the similar operative technique, which forms the standard protocol in our center.
In the first three postoperative weeks, the suture was released when IOP was more than 16 mmHg or at lower pressures if the target pressure for the individual patient was not achieved. If the target pressure was achieved, suture release was delayed beyond 3 weeks. We assumed that 3 weeks was the critical period after which release of the suture would not produce any significant effect. Hence, after this period we attempted to release all sutures; if they could not be released, the corneal end was trimmed.
| Results|| |
From January 1992 a releasable suture technique was used for all patients undergoing primary trabeculectomy or combined cataract extraction in this institution. One hundred and thirty-seven patients (154 eyes) underwent trabeculectomy or combined lens extraction and trabeculectomy. There were 78 males and 59 females. The mean age of the patients was 57 years (S.D. 13.9; range 7 to 85 years). Diagnostic categories of glaucoma are shown in [Table - 1]. Fifty-five eyes underwent trabeculectomy alone while in 99 eyes trabeculectomy was combined with cataract extraction performed through a separate corneal incision [Table - 2]. The mean decrease in IOP following suture release was similar (p = 0.99) in eyes with trabeculectomy alone (mean 6.2 ± 6.7 mm Hg) and in eyes in which a cataract extraction was added (mean 6.4 ± 5.0 mmHg). The distribution of patients according to decrease in IOP for the day of release is shown in [Table - 3]a[Table - 3]b. Although a larger proportion of patients in the trabeculectomy group had less than a 5 mmHg decrease in IOP following suture release, this difference was not significant (p < 0.3; Chi Square test with Yates' correction). For this reason both types of surgery were grouped together in reporting the results.
Of the 154 eyes studied, in 59 (38.3%) the suture was released within 21 days. In 13 eyes (8.4%) where suture release was attempted during this critical period, the suture broke or could not be released. In 82 eyes (53.2%) where the target IOP was achieved, suture release was attempted after 21 days. In 15 of these eyes release was achieved; in the remaining eyes the suture had to be trimmed.
The mean drop in IOP when the suture was released during various postoperative periods is shown in [Table - 4]. If the suture was released within the first 21 postoperative days the mean drop in IOP was 7.0 mmHg,, (S.D. 5.7) (mean pre-release IOP 23.0 ± 9.4 mmHg ; mean post-release IOP 16.0 ± 8.4 mmHg). This decrease in IOP was statistically significant (p<0.01). However, the fall in IOP when the suture was released after 21 days was only 2.3 ± 2.5 mmHg (mean prerelease IOP 13.3 ± 4.8 mmHg ; mean post-release IOP 11.0 ± 3.7 mmHg).
[Figure - 2] shows the distribution according to time of release and fall in IOP. When the suture was released within 1 to 7 days - 70% had a decrease in IOP of more than 5 mmHg; with release after 21 days only 20% had more than a 5 mmHg decrease in IOP.
The mean reduction in IOP with or without the use of antimetabolites is shown in [Table - 5]. Seven of the eyes which underwent trabeculectomy with mitomycin C had sutures released after 21 days. The mean decrease in IOP in these eyes was 1.5 ± 2.2 mmHg. Four of these eyes were released after 28 days with a mean drop in IOP of 0.75 ± 1.5 mmHg.
The complications of the releasable suture technique that we encountered included a windshield wiper keratopathy in 18 (11.6%) eyes [Figure - 3], failure to release the suture during the critical period in 13 (8.4%) eyes, epithelial abrasions in 6 (3.8%) eyes and a sub-conjunctival bleed following release in one (0.6%) eye. The follow-up ranged from 162 days to over two years with a mean of 193 days. None of the operated eyes showed any evidence of bleb infection at the last follow-up.
| Discussion|| |
The advantages of a tightly sutured scleral flap with postoperative titration of filtration after trabeculectomy have led to the development of laser suturolysis and releasable suture techniques. Wilson described a mattress-type scleral flap suture which was externalised with the knot on the cornea. Postoperatively the suture could be cut or removed. Shin fashioned a scleral flap suture utilizing a releasable knot which was passed through the conjunctival bleb. This technique risked subsequent wound leakage. The technique described by Cohen allows ready access to the suture which can easily be removed postoperatively at the slit lamp with minimal cost, pain or inconvenience.
In our series, where eyes required cataract extraction in addition to filtering surgery, this was performed through a separate corneal incision; the construction of the scleral flap and the suture was thus similar to trabeculectomy alone. Also, as the mean fall in IOP and the distribution of such reduction against the day of release was similar in the two groups eyes undergoing trabeculectomy alone and those where trabeculectomy was combined with cataract extraction were considered together for analysis.
The most obvious disadvantage of our study is the fact that a number of surgeons of differing levels of experience performed the operations. A standard technique was followed by all surgeons with no deviation from the established protocol. When we analyzed the fall in IOP following suture release for each surgeon in the first three weeks, we could not detect any statistical difference between surgeons. Thus, we feel that the results are valid and statistically sound. In fact, the number of surgeons makes it similar to a "real-life" situation.
Another possible drawback was the fact that several diagnostic categories of glaucoma were included. Conditions such as glaucoma secondary to trauma where significant inflammation may have affected the outcome of the trabeculectomy could have biased the results. Fortunately, the numbers in these categories are small [Table - 1] and excluding them from the analysis does not change the overall picture that emerges.
The maximum postoperative period during which suture release remains effective has not been previously established. Using laser suturolysis, Savage et al demonstrated a maximum effect at 2 weeks and a moderate effect at 3 to 4 weeks. Other authors have noticed no effect beyond 10 days and some prefer suturolysis within 2 to 3 days after surgery.
In the 59 (38.3%) eyes where the suture was released within the "critical" 21 days, the decrease in IOP following release was significant (mean 7.0 ± 5.7 mmHg; p <0.01). The immediate effect was similar whether the suture was released within the first, second or third week. However, if released within the first week, 70% of eyes had a decrease in IOP of more than 5 mmHg. This decreased to approximately 50% in the second and third postoperative week. If the suture was released within 14 days postoperatively, the reduction in IOP persisted at 1 month.
The optimum time for releasing the suture to obtain an immediate effect is longer in our udy (3 weeks) than that reported for laser suturolysis by Liebermann, who suggested less than two weeks postoperatively, or Melamed who prefers 3 days. A decrease in IOP more than 5mmHg is most likely to be achieved if the suture is released within the first week. This persists at one month after suture release [Table - 4] and supports early release, specifically Melamed's advice of suturolysis within 2 to 3 days for maximum effect.
As we attempted to release all sutures after 21 days, we could obtain some additional information on the effect of release in the late postoperative period. Between 21 and 28 days, the mean reduction in IOP was 2.2 ±2.4 mmHg. This was not statistically significant. Although a statistically significant result was achieved beyond 28 days, the numbers are small and the actual fall in IOP (2.3 ± 2.4 mmHg) is unlikely to be clinically significant. However, there may be individual cases where any further decrease in IOP, however minimal, may help achieve the desired target IOP.
The use of antimetabolites such as mitomycin C or 5-FU during or after trabeculectomy greatly delays normal wound healing., Pappa and associatesshowed a definite clinical effect with laser suturolysis performed 7 to 21 days post-operatively in 5 eyes with adjunctive use of mitomycin C. 5-FU did not seem to have a similar effect. Analysing eyes receiving mitomycin and 5-FU together we could not demonstrate a significant difference in the pressure lowering effect between the eyes with or without adjunctive antimetabolite use. The patients usually received antimetabolites for socio-economic considerations and problems with follow-up rather than for the usual indication of refractory glaucoma. However, the two groups could have varied with respect to other characteristics which may have masked any possible effect of antimetabolites. On suture release within 21 days, eyes receiving mitomycin seemed to have a greater mean decrease in IOP (7.6 ± 5.7 mmHg) compared to eyes receiving 5-FU (5.3 ± 7.7 mmHg). However, the difference was not statistically significant (p = 0.465). Further studies are needed to establish the period of effectiveness of releasable sutures in trabeculectomies with antimetabolites.
Argon laser suturolysis is useful, but has limitations: failure of laser suturolysis due to thick overlying Tenon's capsule; postoperative inflammation; sub-conjunctival hemorrhage and button-holing of the conjunctiva with leakage from the bleb site and secondary hypotony. Savage and co-workers reported that of 38 eyes which underwent argon laser suturolysis, 3 needed surgical reformation of the anterior chamber.
The releasable suture technique for trabeculectomy has the advantage of technical ease and of not requiring a laser. Further, a shallow anterior chamber following suture release was not noted in our series. This could be related to the absence of a "massage effect" created by the lens used to release the suture during laser suturolysis. Releasable suture technique however, has limitations such as inability to release the suture during the critical period which occurred in 13 eyes in our series. It should be remembered, however that laser suturolysis still remains an option in these cases.
Another frequent complication was the windshield wiper keratopathy which occurred due to the rubbing of the suture on the cornea with the movement of the lids. This is a distinctive wedge-shaped keratopathy which resembles the pattern left on a car windshield by the wiper blade and occurs with or without the use of antimetabolites. Although this keratopathy resolves with release or trimming of the suture, there is a potential for infection, and techniques have been described to avoid this complication. Finally, as a track remains when the suture is trimmed, there is always the risk of bleb infection which, however, was not seen to the maximum duration of follow-up in our series.
In our experience, the releasable suture technique is an effective method of titrating postoperative filtration, with maximum effect within the first 3 postoperative weeks. We found the use of antimetabolites did not extend the effective period for suture release. The technique is effective even when a cataract extraction (through a separate corneal incision) is added to the trabeculectomy.
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[Figure - 1], [Figure - 2], [Figure - 3]
[Table - 1], [Table - 2], [Table - 3], [Table - 4], [Table - 5], [Table - 6]