Gelatin implants in glaucoma filtering surgery

The critical role of the conjunctiva in glaucoma filtration surgery

This review considers the critical role of the conjunctiva in determining the success or failure of glaucoma filtration surgery. Glaucoma filtration surgery can be defined as an attempt to lower intraocular pressure (IOP) by the surgical formation of an artificial drainage pathway from the anterior chamber to the subconjunctival space. Many types of glaucoma filtration surgery have been developed since the first attempts almost 180 years ago. The wide range of new techniques and devices currently under investigation is testament to the limitations of current techniques and the need for improved therapeutic outcomes. Whilst great attention has been paid to surgical techniques and devices to create the drainage pathway, relatively little attention has been given to address the question of why drainage from such artificial pathways is often problematic. This is in contrast to normal drainage pathways which last a lifetime. Furthermore, the consequences of potential changes in aqueous humour properties induced by glaucoma filtration surgery have not been sufficiently addressed. The mechanisms by which aqueous fluid is drained from the subconjunctival space after filtration surgery have also received relatively little attention. We propose that factors such as the degree of tissue damage during surgery, the surrounding tissue reaction to any surgical implant, and the degree of disruption of normal aqueous properties, are all factors which influence the successful formation of long term drainage channels from the conjunctiva, and that these channels are the key to successful filtration surgery. In recent years it has been suggested that the rate of fluid drainage from the subconjunctival space is actually the determining factor in the resultant IOP reduction. Improved knowledge of aqueous humour induced changes in such drainage pathways has the potential to significantly improve the surgical management of glaucoma. We describe for the first time a novel type of drainage surgery which attempts to minimise surgical trauma to the overlying conjunctiva. The rationale is that a healthy conjunctiva allows drainage channels to form and less opportunity for inflammation and scar tissue formation which are a frequent cause of failure in glaucoma filtration surgery. Successful drainage over extended periods of time has been demonstrated in monkey and rabbit eyes. Long lasting drainage pathways were clearly associated with the presence of lymphatic drainage pathways. A new philosophy in glaucoma drainage surgery is proposed in which minimisation of surgical trauma to the conjunctiva and the encouragement of the development of conjunctival drainage pathways, particularly lymphatic pathways, are central pillars to a successful outcome in glaucoma filtration surgery.

Trabeculectomy and gelatin implants. A retrospective, long-term follow-up study

In a retrospective follow-up study including 60 eyes with simple or capsular glaucoma, the results obtained by using a gelatin implant under the scleral flap during trabeculectomy were compared with those obtained without such implants. One month postoperatively the mean IOP was significantly lower in the gelatin group than in the control group (15.0 mmHg and 17.9 mmHg, respectively) (p = 0.024). At the long-term follow-up, however, the mean IOP in the two groups were very similar (13.6 mmHg and 14.8 mmHg, respectively).

Glaucoma filtering surgery, a retrospective study of 300 operations

The results of 300 consecutive glaucoma filtering procedures, which were performed in our clinic between January 1982 and September 1985, are described. The overall combined success rate (complete + qualified) was 66.5% (Heuer's classification). This is in good agreement with other glaucoma referral centers. The peak of the age distribution curve at the time of operation was between 70 and 75 years. Nevertheless, 30% of operations was performed on patients under 50 years of age. Relatively poor success rates were obtained in operations following prior unsuccessful filtering surgery (50.5%) or other surgery (47%), in patients under 50 years of age (61%) and in some types of secondary glaucoma. In aphakia/pseudophakia the success rate was 33%. The posterior capsule was intact only 13% of this category at the time of surgery, in 56% previously unsuccessful filtering surgery had been performed, and the age at operation was relatively young (53 yr). These factors have an unfavorable influence on the results of filtering surgery. The success rate in phakic primary open angle glaucoma was 85% and in phakic primary angle closure glaucoma 73%. The combination with a cataract extraction (in 28%) and a peripheral iridectomy, if this had not been performed previously, (in 31%) may have contributed to the relatively favorable surgical results in phakic primary angle closure glaucoma. Relatively high intraocular pressures were found in the early postoperative period; the peak of the pressure-curve was between 20 and 25 mm Hg, 10 mm Hg higher than at the end of follow-up. Postoperative progression of glaucomatous visual field defects was noted in 7%. The most disturbing complication was flat anterior chamber, causing or enhancing cataract formation (in 4 out of 8 phakic patients) and corneal dystrophy (in 2 out of 12 patients). A review of literature is given concerning methods of improving filtration, when the surgical prognosis is poor.