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Year : 1999  |  Volume : 47  |  Issue : 2  |  Page : 117-119

The role of tenonectomy in trabeculectomy

1 VST Center for Glaucoma Care L.V. Prasad Eye Institute, Hyderabad, India
2 Public Health Ophthalmology Service, L.V. Prasad Eye Institute, Hyderabad, India

Correspondence Address:
Chandra G Sekhar
L.V. Prasad Eye Institute, L.V. Prasad Marg, Banjara Hills, Hyderabad 500 034
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Source of Support: None, Conflict of Interest: None

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Purpose: To assess the effect of tenonectomy in further lowering the intraocular pressure (IOP) when combined with trabeculectomy.
Methods: The outcomes and complications in 54 eyes of 54 consecutive patients who underwent trabeculectomy with tenonectomy (group I), and 47 eyes of 47 patients who underwent trabeculectomy without tenonectomy (group II) with matching pre-operative variables were analysed. Results: With a mean follow up of 14.7 8.1 months in group I and 17.4 9.5 months in group II, the post-operative mean IOP in the former group was lower by 2.2 mmHg compared to the latter group (p=0.024). Complications seen were conjunctival buttonhole (one in each group), encysted bleb (two in group I and one in group II), one persistent choroidal detachment, and one ciliary block glaucoma in group I. Conclusion: Tenonectomy when combined with trabeculectomy, results in a lower IOP

Keywords: Trabeculectomy, tenonectomy, intraocular pressure

How to cite this article:
Raihan A, Sekhar CG, Naduvilath TJ, Dandona L. The role of tenonectomy in trabeculectomy. Indian J Ophthalmol 1999;47:117-9

How to cite this URL:
Raihan A, Sekhar CG, Naduvilath TJ, Dandona L. The role of tenonectomy in trabeculectomy. Indian J Ophthalmol [serial online] 1999 [cited 2023 May 30];47:117-9. Available from: https://journals.lww.com/ijo/pages/default.aspx/text.asp?1999/47/2/117/22783

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Pharmacological modulation of wound healing in filtering surgery to lower the intraocular pressure (IOP) is an established practice.[1] The favoured procedure currently seems to be the intra-operative use of Mitomycin-C.[2] Because of the high complications rate, caution has been advocated in the use of Mitomycin-C and attempts have been made to identify the appropriate dosage.[2]

There have been conflicting reports regarding the role of tenonectomy in trabeculectomy. While some studies reported a lower IOP with tenonectomy[3],[4] others did not find any beneficial role of tenonectomy.[5],[6] The purpose of this study was to retrospectively analyse the effect of tenonectomy in further lowering the IOP when combined with trabeculectomy.

  Materials and Methods Top

All patients in this study were subjected to trabeculectomy with or without tenonectomy as primary surgery by one of us (GCS) during the period August 1991-March 1995 at LV Prasad Eye Institute, Hyderabad, India. Patients who had uncontrolled primary open-angle glaucoma (POAG) or chronic angle-closure glaucoma (ACG) were included in this study. Patients were excluded from the study if they had secondary glaucoma, if Mitomycin-C was used, or if follow up was less than 6 months. Patients who had received previous laser treatment such as trabeculoplasty or peripheral iridotomy were not excluded from the study.

A total of 74 of cases were identified in group I (with tenonectomy). Seventeen cases were excluded because of follow up of less than 6 months. Group II (without tenonectomy) cases were identified from the patient database so that the preoperative variables matched with group I. Patient charts were reviewed for age, gender, glaucoma diagnosis, IOP, visual acuity (VA), anti-glaucoma medications, cup-to-disc ratio, visual field status, and follow-up duration.

The surgical procedure was identical in both groups except for the fact that group I had tenonectomy done during trabeculectomy. A limbus-based conjunctival incision was made superiorly 8 mm behind the limbus. The incision was carried through the Tenon's capsule down to the episclera. The incision was then extended laterally and medially for 2-3 clock hours and the Tenon's capsule was dissected from the underlying episclera up to the limbus. Dissection was then carefully proceeded to separate the Tenon's capsule from conjunctiva and then it was excised (group I). In both groups, the remainder of the trabeculectomy was performed in a standard fashion, which included a triangular, half-thickness scleral flap measuring 5x5 mm, and 1x3 mm deep block excision and peripheral iridectomy. The scleral flap was closed with three 10-0 nylon interrupted sutures, one at the apex of the triangle and one at the middle of each side of the triangle. The conjunctival incision was closed with an 8-0 polyglactin suture in a horizontal running mattress fashion.

The postoperative care consisted of topical betamethasone 6 times a day in the first week, tapered off in the next 3 weeks, and topical 1% cyclopentolate 3 times a day for 2 weeks. The postoperative visits were at 1, 3 and, 5 weeks and later 3-monthly or more frequently depending on the clinical condition. At each visit Snellen visual acuity and IOP by Goldmann applanation tonometry were recorded and a detailed slitlamp examination was carried out. Fundus evaluation was carried out with Volk 78 D lens and visual field examinations with Humphrey field analyzer. Visual field scoring was as follows.

The variables in the two groups were compared using the t-test for continuous variables like age, IOP, visual acuity (Snellen acuity converted to logMAR), and follow-up duration, and the Mann-Whitney U test for ranked variables like visual field and medication score. Categorical variables were compared using the chi-square test.

  Results Top

A total of 101 eyes of 101 patients were included in the study. Of these, 54 eyes of 54 patients were in group I (with tenonectomy) and 47 eyes of 47 patients were in group II (without tenonectomy). [Table - 1] shows the preoperative matching between the two groups. There was no statistically significant difference for any variable between the two groups.

Data from the final postoperative visit is shown in [Table - 2]. The mean post-operative IOP in group I (13.32 mm Hg, 95% CI = 12.28-14.36) was significantly less (p=0.024) than the mean postoperative IOP in group II (15.47 mm Hg, 95% CI = 13.89-17.05). Though the mean percent reduction of IOP in group I (42.4, 95% CI = 36.76-48.08) was more than in group II (34.88, 95% CI = 27.35-42.41) it did not reach statistical significance (p=0.115). The number of eyes with a final IOP≤

14 mmHg were significantly more (p=0.042) in group I (64.8%) compared to those in group II (44.7%).

Complications encountered were conjunctival buttonhole (one in each group), encysted bleb (two in group I and one in group II), one ciliary block glaucoma in group I and one persistent choroidal detachment that needed choroidal tapping. The conjunctival buttonholes were managed by suturing with 10-0 nylon. The other complications were successfully managed without affecting the IOP control or the final visual outcome.

  Discussion Top

The search for a safe and effective method of controlling IOP continues. Currently, pharmacologic modulation of wound healing is the preferred technique, but this is not without complications.[1] Tenonectomy has been tried in the past to enhance the success of trabeculectomy with variable results. The purpose of current study was to re-evaluate the possible role of tenonectomy in additional lowering of IOP when combined with standard trabeculectomy without pharmacologic modulation. It was also considered that tenonectomy would also make laser suturolysis easier.

With comparable pre-operative variables in the two groups [Table - 1] the mean post-operative IOP in group I with tenonectomy was significantly lower (p=0.024) than in group II [Table - 2]. This difference of 2.2 mmHg in mean IOP is clinically significant as any additional reduction of IOP protects the optic nerve so long as hypotony is not caused. Since in many clinical situations the target IOP is around 14 mmHg, we looked at the prevalence of IOP≤

14 mm Hg in the two groups postoperatively. This IOP was achieved more frequently with tenonectomy than without, and this difference was statistically significant (p = 0.042). The magnitude of IOP reduction and the percentage of IOP reduction are probably more important than the final IOP in the context of target IOP. Both these parameters were higher in group I as compared to group II, but did not reach statistical significance [Table - 2].

Tenonectomy has in the past been reported to be both beneficial [3, 4] and not beneficial [5, 6] in greater IOP reduction. One would expect a greater chance for conjunctival buttonholing in group I. However, conjunctival buttonholing was encountered once in each group.

Persistent choroidal detachment in one patient and ciliary block glaucoma in another in group I may be incidental as both these are rare complications. Alternatively, the lower IOP in group I may have predisposed the patient to choroidal detachment. Both these complications did not affect the IOP control or the visual outcome.

Thin blebs are produced with pharmacological modulation; therefore, one should avoid tenonectomy in filtering surgery along with pharmacologic modulation.

This study, however, does have certain limitations. With a retrospective study design, changes like bleb appearance could not be recorded accurately. Although in this study, the groups were matched for pre-operative variables, pre-operative randomisation would be a better study design. There is a possibility that the marginally lower IOP in group I is secondary to the shorter follow up in this group.

This study demonstrates a further lowering of IOP in trabeculectomy when combined with tenonectomy as compared to trabeculectomy without tenonectomy.

  References Top

Skuta GL. Wound healing in glaucoma filtering surgery. Surv Ophthalmol 1987;32:139-70.  Back to cited text no. 1
Megevand GS, Salmon JF, Schaltz RP, Murray ADN. The effect of reducing the exposure time of Mitomycin-C in glaucoma filtering surgery. Ophthalmology 1995;102:84-90.  Back to cited text no. 2
Kietzman B. Glaucoma surgery in Nigerian eyes: a five year study. Ophthalmic Surg 1976;7:52-58.  Back to cited text no. 3
Ben Sira I, Ticho U. Excision of tenon's capsule in fistulizing operations on Africans. Am J Ophthalmol 1969;68:336-40.  Back to cited text no. 4
Maumenee AE. Mechanism of filtration of fistulizing glaucoma procedures. In: Symposium on Glaucoma. Transactions of the New Orleans Academy of Ophthalmology. St. Louis: CV Mosby, 1981. p 280-88.  Back to cited text no. 5
Kaptenasky FM. Trabeculectomy, or trabeculectomy plus tenonectomy:a comparative study. Glaucoma 1980;2:451-53.  Back to cited text no. 6


  [Table - 1], [Table - 2], [Table - 3]


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