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Year : 1983  |  Volume : 31  |  Issue : 5  |  Page : 615-618

Minimizing filteration surgery failure

Deptt. of Ophthalmology., Medical College, Amritsar, India

Correspondence Address:
Daljit Singh
Deptt. of Ophthalmology., Medical College, Amritsar
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Source of Support: None, Conflict of Interest: None

PMID: 6671775

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How to cite this article:
Singh D, Singh KD, Sood R, Singh J. Minimizing filteration surgery failure. Indian J Ophthalmol 1983;31:615-8

How to cite this URL:
Singh D, Singh KD, Sood R, Singh J. Minimizing filteration surgery failure. Indian J Ophthalmol [serial online] 1983 [cited 2019 Dec 12];31:615-8. Available from:

Table 1

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Table 1

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Failure after filteration surgery for glaucoma is a fairly common experience with every ophthalmologist. The rate of failure varies from surgeon to surgeon and depends mainly upon their ability to follow and document failures.

The sheet anchor of glaucoma treatment in our predominantly rural society is filteration surgery. The economic hardships associated with prolonged medication, coupled with uncertain availability of medicines are other important reasons why more patients will need early surgery. Thus it becomes imperative that we are able to minimize our surgical failures.

A detailed study on the causes of failure in glaucoma has already been reported (Singh et al 1979)[1] . The main causes of failures have been divided into following three groups:

Group 1:

Only one factor is responsible for the surgical failure. It could be a wrong choice of operation (doing peripheral iridectomy where filteration was indicated). The internal opening of the filteration could be blocked by iris, lens matter, vitreous or blood etc. The scleral wound could heal up completely. Further there could be scarring of the subconjunctival tissues which would not allow filteration.

Group 2:

The failure is caused by three types of double combinations:

a) Subconjunctival + intraocular causes.

b) Subconjunctival + scleral causes.

c) Scleral + intraocular causes.

Group 3:

There is a combination of all three factors, i.e. subconjunctival, intraocular and scleral.

The percentage of patients belonging to Groups 1, 2 and 3 has been found to be 24.8%, 62.4% and 12.8% respectively.

The most important causes responsible for filteration failures, either singly or in combina­tion as found were as follows:

1. Blockage of the internal opening by iris tissue: 58%.

2. Scarring under the conjunctiva: 56.8%.

3. Closure at the scleral edges: 32%.

4. Uveitis: 6.9%.

Taking these bugbears into consideration, we have modified the surgical management of our glaucoma cases as follows:

1. A fornix-based flap lifting conjunctiva and Tenon's capsule as one piece. A radial cut is given in the conjunctiva at 10.30 O'clock. The conjunctiva is cut at the limbus with a scissors. The incision is finished with another radial cut at 1.30 O'clock. The fornix based flap is retracted upwards for about 7 mm.

2. Minimum cautery is applied on the surface of the sclera, so as to destroy the blood vessels in the line of proposed scleral incision for pretrabecular-filteration [2] .

3. The thickness of the scleral flap is kept at less than 1/2 scleral thickness. Any bleeding point is cauterized.

4. The cleaning of the surgical field is done mostly with a stream of Lactate Ringer solution. A cotton swab stick is rarely employed.

5. The incision is made with an extremely sharp stainless steel blade developed by one of the authors (DS). The pretrabecular square opening made by this blade has very clean edges.

6. Iridectomy is done by a new technique developed by the author (DS). It is as follows: When the pretrabecular opening has been completed, the iris tissue generally buldges into the opening. It is pushed back into the anterior chamber and all the aqueous is drained out. The iris tissue is then grapsed with a forceps at the posterior edge of the opening and is pulled anteriorly towards the centre of the cornea and is then cut with the scissors [Figure - 1]. The area of the opening is washed with a stream of Lactated Ringer. The size of the iridectomy is rather on the larger side. The pretrabecular opening is inspected for the absence of iris.

7. The scleral flap is closed with a single stainless steel suture.

8. At this stage the anterior chamber is irrigated with Lactated Ringer to wash out any pigment or blood. The anterior chamber gets formed in this process.

9. The conjunctival flap is stitched back with stainless steel at 10.30 O'clock and 1.30 O'clock.

The surgery is done under magnification of 2X, 6X or 10X.

10. Subconjunctival injection of 2 mgm dexamethasone is given.

Post-operatively, local steroids are instilled for one to two weeks.

The technique as described above has been used in 134 eyes of 122 patients. More than half the operations have been done by the residents. The follow up period varies from 2 to 14 months.

Table No. 1 shows age and sex distribution,

The various types of glaucoma were as follows

1. Chronic simple glaucoma 26.1%

2. Acute congestive glaucoma 17.2%

3. Chronic conjestive glaucoma 13.4%

4. Lens induced glaucoma 22.4%

5. Aphakic glaucoma 13.4%

6. Secondary glaucoma 4.5%

7. Absolute glaucoma 1.5%

8. Neovascular glaucoma 0.75%

9. Buphthalmos 0.75%

Immediate post-operative complications were as follows:

Shallow anterior chamber .. 5.2%

Hyphema .. 2.2%

Iritis .. 1.5%

  Observations Top

The ocular tension was brought under control, (less than 21 mm. Hg.) in 91.5% of the patients. Another 6% were further controlled with local pilocarpine drops. Only 2.5% were advised reoperation.

  Discussion Top

The selection of a filteration procedure is a matter of personal choice by individual surgeon, his surgical training and his own experience. But it will not be wrong to say that a modern glaucoma operation would involve the making of a filtering track under a scleral flap. Trabe­culectomy and pretrabecular-filteration are examples of this trend.

Let us discuss the various points mentioned by us regarding minimizing surgical failures:

1. Conjunctival flap: A limbus based conjunc­tival flap cuts the conjunctiva as well as the conjunctival vessels going towards the limbus. The flap is thus devoid of circula­tion for some time atleast. This to our mind is one reason for getting avascular thin blebs that are so prone to infection.

A limbus based flap also mutilates the Tenon's capsule. It is not possible to bring the Tenon's capsule back to its original place at the end of operation. Cutting the Tenon's capsule stimulates scarring and strangulation of capillaries that are important for drainage.

A limbus based conjunctival flap in a heavily trachomatous population like ours is prone to excessive scarring. When there is shrinkage of the fornix, even the making of such a flap is unsatisfactory.

The closure of the limbus based conjunctival flap is not complete with 2 or 3 stitches as is the usual practice. The removal of sutures is also tedious.

A fornix based conjunctival flap has all the plus points: the ease of making a flap even under the most difficult circumstances including the shrinkage of conjunctiva, no damage to the Tenon's capsule and a beautiful replacement of the flap back to the original site. There is no interference with the vascular supply of the flap.

2. Excessive cautery and the use of cotton tipped swabs over the sclera are important causes of scar formation. A fornix based flap is less trouble some in terms of bleeding. Lactated Ringer used as a steady flow of drops helps keep the field clean without leaving any contamination as can occur with cotton.

3. A sharp blade not only makes a clean cut in the sclera, but also makes a pretrabecular opening safely. Ragged scleral incision will cause excessive bleeding as also injure the tissues unnecessarily. A blunt pointed knife is not easy to manage, since the amount of pressure cannot be regulated. Such a knife may make a sudden entry into the anterior chamber and may pierce through not only the iris but also the lens, causing untold miseries to the surgeon as well as to the patients. The superb stainless steel blade introduced by the author (DS) overcomes all these difficulties.

4. Iridectomy: If it is realized that more than half of the failures of filteration surgery are caused by faulty iridectomy, resulting in the iris plugging the internal hiatus, the importance of a more reliable iridectomy will be readily appreciated.

The way iridectomy is generally done is like this.:

a) The iris is lifted out of the opening and cut.

b) The iris is pulled posteriorly and cut. Most surgeons tend to do small iridectomies.

The new way to do iridectomy as described in step 6.

5. Stainless steel suture used to close the scleral flap makes an extremely small knot which does not eroded through the overlying conjunctival flap. Further it is the only totally inert suture material.

6. Washing the anterior chamber with Lactate Ringer solution removes any loose pigment released by iridectomy and other manipulations. It is well known that pigmented races show a higher tendency to post-operative uveitis and subconjunctival scarring. Thus it would be wiser to clear away as much of the loose pigment as possible.

It would thus appear that the subject of filteration surgery for glaucoma is stil very much open for further research. The little innovations introduced in our filteration surgery have improved results even in the hands of less experienced residents, who did more than half the present series of cases. A wider use of these little points might prove useful at other centres too.

  Summary Top

For minimizing the failure in filteration surgery, the role of a fornix based conjunctival flap, extremely sharp blade minimal scleral cautery and the use of Lactate Ringer to clean the field of surgery and to wash the anterior chamber are discussed. A new way to do iridectomy has been discussed. The iris is held at the posterior edge of the opening and is pulled anteriorly before being cut. This step clears the area of internal hiatus of all iris tissue and ensures free flow of aqueous into the filteration opening.

  References Top

Singh, D. Verma, A. and Singh, M., All India Ophthalmology Society Under Publication, 1979.   Back to cited text no. 1
Singh, D., Nirankari, M.S. and Singh, M., Pro­ceedings of All India Ophthalmology Society, Vol. 33, p. 161, 1977.  Back to cited text no. 2


  [Figure - 1]

  [Table - 1]


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