|Year : 1985 | Volume
| Issue : 5 | Page : 277-279
A clinical study of filtering blebs
Manoj Shukla, Nasir Jamal
A.M.U. Institute of Ophthalmology Aligarh, India
A.M.U. institute of Ophthalmology, Aligarh
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Shukla M, Jamal N. A clinical study of filtering blebs. Indian J Ophthalmol 1985;33:277-9
The success of surgical intervention in glaucoma primarily depends on the functional integrity of the filtering bleb. The aim of the present investigation was to study the different morphological and functional aspects of the filtering bleb after surgery for primary glaucoma.
| Material and methods|| |
The present study includes 56 eyes having uncontrolled open angle glaucoma (51 eyes) and acute congestive glaucoma (5 eyes). Posterior lamellar sclerectomyPLS (Pretrabecular Filteration), was undertaken in 50 eyes while Schie's procedure was attempted in 6 eyes. Postoperatively the eyes were examined for inflammation, depth of the anterior chamber and a special attention was paid to study the character of the filtering bleb. Intraocular pressure was recorded by Schiotz tonometer and a detailed morphological evaluation of the filtering bleb was made 8-10th day after surgery under slit lamp. Any further change in the morphological character of the filtering bleb was noted on subsequent follow up visits in 42 eyes available for periodic observations from periods varying from 8 weeks to 2 years. The late morphological appearance of the bleb was correlated with the intraocular pressure measurements.
| Observations|| |
The following observations were made in the present study.
1. Site of Bleb
In general, the site of the bleb was between 11.30-12.30 O'clock It was closer to limbus in Schie's procedure while it was located slighty away from limbus in PLS in a large majority of the eyes.
2. Size of Bleb
In eyes operated for PLS, the size of the bleb as seen 8-10th day after surgery varied between 5-10 mm [Figure - 1] while in Schie's procedure it varied from 2.5-5 mm [Figure - 2] On three months follow up examination which was available for most of the eyes, the size of the bleb was found to be markedly reduced to 4-6 mm and 2-4 mm-respectively.
3. Shape of Bleb
The bleb was cystic and globular in eyes operated for Schie's procedure while it was diffuse, non-cystic and more or less round in PLS. The surface and interior of the blebs were examined under high power by focal illumination, On follow up examination (after 3 months), the bleb became smaller and was seen as a tiny elevation at the limbus in Schie's operation and a relatively flatter looking area at the limbus in PLS. In some of the eyes operated for PLS where follow up examination was available for more than six months, it was rather difficult to identify the filtering bleb by a naked eye examination alone although the intraocular pressure was nicely controlled (below 20 mm of Hg).
4. Condition of Conjunctiva and Tenon's Capsule
In early postoperative period there is chemosis, conjunctival congestion and episcleral congestion. These are more prominent in PLS than Schie's procedure. In both the procedures, conjunctival edema and congestion become progressively less marked with passage of time and the area of the bleb typically appears more or less anaemic although some congestion around this anaemic area can be seen being more marked in PLS than Schie's procedure.
5. Anterior Chamber Depth
In eyes operated for PLS, the anterior chamber remained formed in all but three eyes postoperatively. In 5 eyes operated by Schie's procedure the anterior chamber remained shallow in four eyes postoperatively. The anterior chamber subsequently formed in both the groups following medical treatment.
6. Intraocular Pressure
Intraocular pressure was controlled in all but one eye (30 mm PLS) as recorded 8-10th day after surgery. 4 eyes bad intraocular pressure between 20-25 mm of Hg while the remaining 51 eyes had a intraocular pressure less than 20 mm of Hg. Follow up examination (8 weeks to 2 years, average 3 months) was available in 42 eyes which revealed excellent control of intraocular pressure (10-20 mm of Hg in 36 eyes and less than 10 mm of Hg in 6 eyes).
7. Abnormal Morphological changes in the bleb
Except for changes in shape, size and consistency of the bleb, we did not observe infection, rupture or cystoid cicatrisation of the bleb on follow up examinations. Although in 17 eyes operated for PLS, the area of the bleb appeared more or less flat [Figure - 3], the intraocular pressure was nicely controlled.
| Discussion|| |
The development and application of scleral flap surgery in the management of glaucoma has greatly reduced the complications associated with the filtering bleb. The complications like infection, rupture, sclerosis and cystoid cicatrisation of the bleb as seen frequently after conventional filtering surgery like Schie's procedure, iridencleisis and trephine are never seen Further, delayed or non formation of the anterior chamber is perhaps rarely seen in contrast to its frequent occurence after conventional filtering surgery. The most important factor undoubtedly is a scleral support to filteration which is responsible for the diffuse nature of the bleb after surgery. Generally speaking, the bleb undergoes morphological changes in size, shape and consistency with passage of time as the filteration becomes controlled. Even with a flatter looking PLS bleb, the intraocular pressure remains nicely controlled. Accordingly it should be emphasised that a flatter looking filtering bleb after a scleral flap filtering operation does not necessarily mean a surgical failure. The functional status of the filtering bleb is also related to the postoperative use of oral short acting steroids in low doses. In the present series nearly all the eyes operated by PLS received oral prednisolone (10 mg) daily for one week postoperatively. This was perhaps another reason for a reasonably good filtering bleb and control of intraocular pressure in these eyes. When we compared, these results with a group of eyes (unpublished data) operated by PLS where no oral steroids were given postoperatively, there was a definite statistical evidence that the functional integrity of the bleb was superior in the former group of eyes. The use of systemic steroid possibly has a beneficial effect vis-a-vis patency of the filtering cleft by virtue of their inhibitory effect on the process of wound healing. We are currently performing a double blind randomised clinical trial to know precisely the role of systemic steroids following scleral flap surgery for primary glaucoma. The beneficial effects of topical and systemic steroids in achieving a good functional filtering bleb after filtering surgery has been reported by other authors., In this connection, the postoperative use of subconjunctival injections of steroids is also worth evaluating.
In light of observations made in this study, we would strongly recommend that posterior lamellar sclerectomy or pretrabecular filteration or trabeculectomy should be undertaken as a routine for the surgical management of adult primary glaucoma in view of excellent control of intraocular pressure on account of different advantages afforded by the filtering bleb.
| Summary|| |
The filtering blebs in 56 eyes operated for adult primary glaucoma were critically analysed in the present study. Various early and late morphological changes observed in the bleb have been described and discussed. The functional aspect of the filtering blebs was studied vis-a-vis control of intraocular pressure. It is emphasised that a filtering bleb after a scleral flap glaucoma surgery is definitely superior, both morphologically and functionally to that seen after conventional glaucoma surgery.
| References|| |
Ahuja. O. P. and Shukla, M, 1980, J, of Ophthalmol, U.P. 8 : 1.
Singh, D., Nirakari, M.S. and Singh, M, 1977, Proc. All Ind; Ophthalmol Conf.
Kronfeld, P, 1961, Trans. Amer. Ophtal. Soc. 62:375.
Lowe, R, 1966, Trans. Ophthal. Soc. Aust.. 25:39.
[Figure - 1], [Figure - 2], [Figure - 3]