Late bleb needling

Surgical manipulation of the trabeculectomy bleb has become a recognised postoperative procedure to increase the success of glaucoma surgery. The first needling revision of a glaucoma drainage bleb was described in 1941¹ and there are several reports of the successful restoration of failing blebs within the first 3 years following trabeculectomy.^2–6

We report the results of five cases of late bleb needling with 5-fluorouracil (5-FU) where trabeculectomy had been performed between 8 and 30 years earlier.

Case reports

The demographic details of all cases are summarised in Table 1.

Table 1.

Demographic details of patients

Case no			Drainage procedure	Delay to needling (years)	No of needlings	No of 5-FU injections
1	72	M	Bilateral Scheie’s	31	2	4
2	88	F	Left ECCE+trabeculectomy	10	4	5
3	80	F	Right trabeculectomy	12	1	4
4	35	M	Right trabeculectomy	8	1	2
5	71	M	Bilateral trabeculectomy	13	1	2

ECCE = extracapsular cataract surgery.

Glaucoma surgery had taken place between 8 and 31 years before bleb needling and in no case had antimitotics been used at the original surgery. Before bleb needling the average intraocular pressure (IOP) among the patients was 29.4 mm Hg (range 19–58). Each patient showed glaucomatous deterioration despite being on maximum tolerated medical therapy, taking on average three ocular hypotensive agents, and in two cases oral acetazolamide. In all cases an open sclerotomy was confirmed by gonioscopy.

All procedures were performed in the outpatient clinic, by either a consultant or associate specialist, using a slit lamp. The eye was anaesthetised with amethocaine eye drops 1%, and phenylephrine eye drops 2.5% were used for vasoconstriction. After several drops of chloramphenicol the conjunctiva was entered several millimetres from the flap site with a 27 gauge needle mounted on an insulin syringe. In one case aqueous flow was established after perforating scar tissue around an encysted bleb, whereas in the others it was necessary to dissect beneath the scleral flap and enter the anterior chamber. After creating a bleb and confirming a reduction in IOP by applanation tonometry, 5 mg 5-FU (25 mg/ml) were injected into the subconjunctival space around the bleb. After needling, all hypotensive therapies were stopped and replaced by intensive topical steroids and chloramphenicol. The steroid was titrated, and repeat injections of 5-FU with or without needling were given, according to the IOP and appearance of the bleb.

After 12 months’ follow up from the last needling (Table 2), average IOP was reduced to 14 mm Hg (range 9–17). There was no change in the patients′ visual acuity. Two cases developed a mild corneal epitheliopathy that healed within 8 weeks. There were no other complications from the needling procedure.

Table 2.

Results of pre-bleb and post-bleb needling with a 12 month follow up period

Case no	Age (years)	Sex	IOP (mm Hg)		No of medications
			Pre	Post	Pre
1	72	M	19	9	3+ acetazolamide	0
2	88	F	25	14	3	1
3	80	F	20	17	3	1
4	35	M	58	12	2+ acetazolamide	0
5	71	M	25	16	2	0

Comment

Although trabeculectomy is the preferred glaucoma drainage procedure, only 67% of patients may achieve an adequate target pressure after 1 year.⁵

In recent years glaucoma surgery has developed with the use of antimitotics and intense postoperative surveillance with bleb manipulation. Reports show that bleb needling used in combination with subconjunctival 5-FU injections can rectify a failing bleb in the early postoperative phase but there are few reports confirming its effect in the late postoperative period.^2,3 Some studies have indicated that the success of bleb needling is unrelated to the time lapsed from the original surgery^2,3 though in these studies the maximum interim period was less than 4.5 years.

The patients presented in this study had had their original glaucoma surgery at least 8 years previously and bleb needling was carried out before listing the patient for a repeat trabeculectomy with mitomycin C. The only adverse effect noted was a temporary corneal epitheliopathy, probably related to toxicity of the 5-FU. Other reported adverse events after bleb needling include hyphaema, bleb leak, shallow anterior chamber, choroidals effusion and endophthalmitis, but there are no reports of long term hypotony as has been described following mitomycin C trabeculectomy.

These case reports indicate that bleb needling may be successful in achieving a long lasting IOP reduction even several years after the original surgery. The procedure does not require dextrous skills beyond that of a trained general ophthalmologist. It appears at least as safe as trabeculectomy and avoids a formal operation. If it does fail the surgical field is still intact for a “redo” trabeculectomy.