|Year : 1971 | Volume
| Issue : 2 | Page : 52-54
Failure of filtering bleb after threphination and its management
Eye Surgeon, ESI Hospital, Coimbatore, India
Eye Surgeon, ESI Hospital, Coimbatore
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Sivaramasubramanyam P. Failure of filtering bleb after threphination and its management. Indian J Ophthalmol 1971;19:52-4
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Sivaramasubramanyam P. Failure of filtering bleb after threphination and its management. Indian J Ophthalmol [serial online] 1971 [cited 2021 May 12];19:52-4. Available from: https://www.ijo.in/text.asp?1971/19/2/52/34992
In wide angle glaucoma, the main accepted fact is that the filtering angle is affected, but why or how is not yet clearly known. So non-specific operations which produce filtering blebs or decrease the secretion are attempted. The usual filtering operations done are trephination, iridencleisis or Schie's operation. Such varied procedures devised indicate that no single procedure can claim 100 % results.
The average of success that is a reduction of intraocular pressure, taken from a number of stastical reports is 73%. In the remaining 27% reoperations are required, the operation may have to be repeated a second, third or fourth time (Stellard).
Following trephination, a good filtering bleb is usually noted. It is dome-shaped, cystic and extends for 2 to 3 mm all round the trephine hole. But a nonfiltering bleb, on the other hand, is solid, white and flat and does not extend beyond the trephine hole. It is associated with a well formed anterior chamber and increased intraocular pressure.
The causes of failure of fitering blebs following trephination are as follows:
(a) Intraocular causes - Plugging of the trephine hole by iris, ciliary processes, lens or vitreous.
(b) Scleral causes: - Closure of the scleral hole by fibrous tissue.
(c) Subconjunctival causes. - Scarring and condensation of Tenon's capsule.
Proper precautions taken during the operation increases the success rate. Since the closure is associated with the sticking of the conjunctiva and episclera, the Tenon's capsule should be opened at a different level, 4 mm from the limbus, while the conjunctival incision is made near the fornix. The Tenon's capsule can be displaced so that it covers the trephine hole. This prevents the closure of the wound by the conjunctva. Werner suggested the use of a small thin gel film of the size of 6 mm X 4 mm X 0.075 mm over the trephine hole. The posterior end of the gel film is tucked behind the Tenon's capsule. The gel film is non-antigenic and gets absorbed within 6 months.
To prevent incarceration of iris, the trephine blade should be slowly removed after trephination so that the aqueous does not sweep the iris forward as it gushes out of the trephine hole. After the operation, the iris is replaced back in position by gently stroking the cornea with a spatula till the pupil is round. Incarceration by ciliary processes, lens or vitreous are uncommon in limbal trephination of sugar. Also the premedication with glycerol and diamox facilitates by lowering the intraocular pressure to operative level.
Once a filtering bleb is found to be non-functioning, then the cause can easily be detected by gonioscopy and the management of the case depends upon the cause of failure and the duration of raised intraocular pressure. The methods followed by Fitzgerald and Macarthy are simple and successful.
If a well elevated diffuse bleb is not seen upto 2 weeks, the easy procedure of springing of the wound edges can be attempted. This can be done manually with fingers or with sterile glass rods. In quite a number of cases this procedure works well.
If the case is seen between 2 to 4 weeks, needling of the flattened bleb can be done in order to establish external filtration. Under local anaesthesia, the needle knife is passed beneath the conjunctiva to enter sub-conjunctivally a few millimeters from the temporal margin of the flattered bleb and directed horizontally along its interior margin. This then is passed superiorly upwards along the superior margin. Though this is a blind method, it works well in a few cases. Care should be taken to avoid injury to the filtering mechanism.
If this manouvre fails, the exploration of the original operative site is indicated. A limbal based conjunctiral flap is turned down. If the original wound has closed, no leakage of aqueous occurs. Gentle separation of the wound edges will result in drainage of aqueous. The incision is enlarged with a sharp knife and an additional sclerectomy of the anterior lip and/or diathermy of the posterior lip are done. Conjunctiva and Tenon's facia are closed in 2 seperate layers.
If the case is seen after the 16th week, reoperation by another fistulising procedure is necessary. If the trephine hole is blocked by iris tissue, exploration of the wound followed by excision of iris tissue reforms a good filtering bleb.
The following cases operated at the Erskine Hospital, Madurai, illustrate the procedures adopted in a few cases.
| Report of Cases|| |
Case: 1 (gl. No. 3402/69). On 6-9-69 a male patient attended the glaucoma clinic. He had open angle glaucoma with an intraocular tension of 50 mm Schiotz. Trephination was done on 7-9-69. Review on 25-9-69 showed that the intraocular pressure was 28 mm and gonioscopy indicated that the iris was blocking the trephine hole. On 26-9-69 the wound was explored following a limbal based conjunctival flap. The iris plugging the hole was excised and air put in the anterior chamber. The conjunctival flap was sutured. The tension fell to 14.6 mm Schiotz and was maintained.
Case: 2 (gl. No. 2902/69). On 30-1-69 trephination was done for this case of wide angle glaucoma seen on 24-1-69, The initial intraocular pressure of 32.2 mm Schiotz rose to 50 mm post-operatively. Gonioscopy revealed closure of the trephine hole by fibrous tissue. Hence on 18-2-69 under glycerol and diamox, an exploration of the wound was done. The wound was extended on either side for 2 mm with a sharp knife and anterior sclerectomy was done. The wound was closed in layers. The intraocular pressure was maintained normal post-operatively.
Case:3 (gl. No. 2982/69). This patient first visited the glaucoma clinic on 10-2-69. She had open angle glaucoma with an intraocular pressure of 43.4 mm Schiotz. Trephination was done on 13-2-69. Review on 8-3-69 showed that the trephine hole was closed by fibrous tissue and the intraocular pressure was 30.4 mm. Reopening of the wound was followed by extending the hole by 2 mm on either side. This was followed by cauterisation of the posterior lip of the wound with cautery as in Schie's operation. The tension was normalised and maintained.
| Summary|| |
The management of faulty filtering blebs following Trephination is discussed and their causes enumerated. The simple procedure of bleb surgery is illustrated with cases.
| References|| |
FITZGERALD J. R. and MC CARTHY J. L.: Surgery of the filtering blebs, Arch. Ophthal. (Chicgo) 68, 453-467 1962.
MC CULLOCH, C: The incision of inadequate filtration blebs, Trans. Canad. Ophthal SOC 10: 45, 1958.
SUGAR, H. S.: The glaucomas, Hoebar inc. Medical book New York, p 411, 1957.
STELLAND H. B.: Eye Surpery, John wright & Sons Ltd., Bristol pp. 644-645 (1958).