implants for draining neovascular glaucomabritish journalofophthalmology, 1977, 61, 120-125 implants...

British Journal of Ophthalmology, 1977, 61, 120-125

Implants for draining neovascular glaucomaA. C. B. MOLTENO, M. M. B. VAN ROOYEN, AND R. S. BARTHOLOMEW

From the Departments of Ophthalmology of the University of Stellenbosch and Tygerberg Hospital andthe Department of Ophthalmology of Edinburgh University

SUMMARY The implant design, surgical technique, and pharmacological methods of controllingbleb fibrosis, used to treat neovascular glaucoma, are described, together with the results of 14operations performed on 12 eyes.

Established glaucoma with iris neovascularisationand a medically uncontrollable intraocular pressurecarries such a poor prognosis that treatment isusually limited to the retrobulbar injection ofalcohol or enucleation-even in the presence ofslight residual vision. One of us (A.C.B.M.)developed a series of draining implants for use insevere and complex cases of glaucoma (Molteno,1969a, b; 1970; 1973a, b; Molteno et al., 1976a, b).This communication reports the design of implantand the surgical technique currently used to treatcases of neovascular glaucoma at the TygerbergHospital glaucoma clinic and at the University ofEdinburgh.

Principles of implant

Among the first attempts to drain cases of glaucomaby an artificial device was that of Zorab (1912),who connected the anterior chamber to the sub-conjunctival space by means of a silk thread whichacted as a 'conducting wick'. This operation ofaqueoplasty gave long-term control of intraocularpressure in some cases (Martin and Zorab, 1974).This work has been followed by numerous attemptsto drain glaucomatous eyes by a wide range ofdevices, which can be classified as follows:

(1) Translimbal tubes of various materials con-necting anterior chamber to subconjunctivalspace.

(2) Sheets of gel film and other materials placedbeneath the conjunctiva over a conventionaldrainage operation fistula (e.g., cornea-scleraltrephine hole or iridencleisis opening) in orderto promote the formation of a large bleb.

(3) Implants of various materials inserted tomaintain the patency of cyclodialysis clefts.

Address for reprints: Dr A. C. B. Molteno, Faculty of Medicine,University of Stellenbosch, PO Box 63, Tygerberg 7505, Republic ofSouth Africa

(4) Devices draining vitreous from eyes withabsolute glaucoma.

Glaucoma implants are reviewed by Ellis (1960),and other recent publications in this field includethose of Epstein (1959), La Rocca (1962),MacDonald and Pierce (1965), and Blumenthalet al. (1970).

Specifications and mode of action of implants

Our current implant utilises an artificial translimbaltube combined with bleb spreading plate. Thetranslimbal tube of silicone rubber is 16 mm longand has an internal diameter of 0 30 mm and anexternal diameter of 0-63 mm. It is firmly attachedto and opens on to the upper surface of a thincircular acrylic episcleral plate (Stellon brandpolymethyl methacrylate) 13 mm in diameter, whichhas a thickened rim 0 7 mm in height around thecircumference. This rim is perforated for attachmentof the translimbal tube and to allow passage ofsutures which fasten it in position on the globe(Fig. 1).When used to drain a case of glaucoma, the

episcleral plate is sutured to sclera and buriedbeneath a thick flap of Tenon's capsule and con-junctiva. The translimbal tube is trimmed to thecorrect length and inserted into the anterior chamberafter being buried under a lamellar scleral flap.During the first few days after operation the epi-scleral plate becomes surrounded by a thin layer ofvascular connective tissue which impedes the flowof aqueous away from the plate and causes theintraocular pressure to rise. The increasing pressurecauses this fibrovascular 'bleb lining' to becomedistended and to be stretched by a force that isdirectly proportional to the product of intraocular(= to intrableb) pressure and radius of curvatureof the 'bleb lining' (Young, 1805; Laplace, 1807).

Consequently, if this 'bleb lining' can be prevented120

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FIBROVASCULARBLEB WALL

PLATE

Fig. 1 Situation and pr-inciple ofdraining implant

from becoming too thick (by administration of acombination of anti-inflammatory agents), and ifthe radius of curvature of the bleb lining can bemade large through the presence of a large episcleralplate, then a normal intraocular pressure causesprogressive stretching and enlargement of this bleblining until the increased area available for drainageof aqueous so lowers the intraocular (and intrableb)pressure that the bleb lining no longer stretches.This situation results in long-term control of intra-ocular pressure at a level which depends directlyon the area of bleb available for drainage andinversely on the thickness of the fibrous inner bleblining.

Case selection

We hesitated to operate on eyes with neovascularglaucoma, since a drainage operation with insertionof foreign material (albeit inert plastic) into aninflamed eye containing infarcted retina is a situationwhich, in theory, is likely to cause sympatheticophthalmitis. However, after being forced to operateon two only eyes and on a patient with bilateraldiabetic retinopathy in whom the glaucomatous eyesaw better than the normotensive eye we havegradually relaxed our criteria for operation, so thatwe operate in the presence of a good fellow eye ifthe eye has light perception and if the patientchooses an implant after having the dangers pointedout to him and after having been offered a quick andsafe end to his pain through enucleation.

All 12 eyes drained by implants had iris neo-

vascularisation, corneal oedema, and severe pain.Intraocular pressures on full doses of acetazolamide,glycerol, and gutt. adrenaline tartrate (Epitrate) 2%varied from 42 to 75 mmHg, while in 6 of the casesfree blood was present in the anterior chambers.Visual acuity of these eyes varied from light per-ception only in 9 eyes through counting fingers at2 m (1 eye) at 5 m (1 eye) to 3/60 (1 eye).

In 2 cases the underlying pathology was con-sidered to be chronic angle closure glaucoma withsecondary central retinal vein occlusion. In 5 casesvein occlusions occurred without obvious localcause, while in the remaining 5 cases iris neovascu-larisation was associated with grade IV diabeticretinopathy. Both patients with primary angleclosure glaucoma were healthy, but of the remaining10 cases, 9 patients had serious general diseaseincluding myocardial ischaemia in 3 cases, vascularhypertension in 1 case, and severe diabetes in 5cases. Of the diabetics 3 had markedly elevatedblood urea levels and proteinuria as a result ofadvanced diabetic nephropathy.

Surgical technique

Cases were prepared for operation with a combina-tion of gutt. adrenaline tartrate 20 every 30minutes for 2 hours before operation, acet-azolamide 250 to 500 mg intravenously 1 hour beforeoperation, and mannitol 10%0 solution 100 to 400 mlby slow intravenous infusion. starting 30 minutesbefore operation, to lower the intraocular pressureas much as possible.

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A. C. B. Molteno, M. M. B. Van Rooyen, and R. S. Bartholomew

Fig. 2 Insertion of implant. Adeep lamellar scieral flap has beendissected up to the limbus(patient 8)

Anaesthesia

General anaesthesia was preferred, but when thegeneral condition was poor operations were doneunder neurolept analgesia and local injection of 2%lignocaine retrobulbarly and over the condyle ofthe mandible.

Dissection and placing of implants

After inserting a speculum and passing a suturebeneath the superior rectus muscle near its insertionthe globe was rotated so as to expose the supero-nasal or supero-temporal quadrant. The conjunctivaand Tenon's capsule were separated from the limbusand a large fornix-based flap raised and dissectedposteriorly to expose the insertions of superior andmedial (or lateral) rectus muscles and gain access toTenon's space.

After cleaning sclera and cauterising all bleedingpoints in the exposed quadrant a large squarelamellar flap of sclera was dissected up and reflectedat the limbus, care being taken not to enter theanterior chamber (Fig. 2). The implant was thenplaced in position and the episcleral plate suturedfirmly to sclera, using two anterior suture holes andinterrupted mattress sutures of 7-0 silk. The nextstep was to cut off the tube so that the end over-lapped the cornea by 2 to 3 mm (Fig. 3). Theanterior chamber was entered by a circumferentiallimbal incision under the lamellar flap using a no. 11Bard Parker blade and a broad or large peripheraliridectomy performed without any special precau-

tions to prevent bleeding. The free end of the siliconetube was then inserted into the anterior chamber,and after it was arranged to lie free in the centreof the iridectomy it was firmly fastened in thisposition by means of a 7T0 silk suture passed aroundthe tube, through the lamellar flap, and tied tightlyso as to prevent the tube becoming displacedsideways, being withdrawn from the anteriorchamber, or sliding further into the anteriorchamber and touching the central corneal endo-thelium (Fig. 4).

Closure

After the scleral flap had been sutured into positionby 4 interrupted sutures of 6-0 silk, Tenon's capsulewas drawn forward over the episcleral plate of theimplant and sutured to sclera near the limbus, whilethe conjunctiva was held in apposition to the limbusby a 7-0 silk suture at each corner of the flap. Theoperation was completed by injecting a mixture ofgentamycin, cephalosporin, and methylprednisolone(Depot Medrol) beneath the conjunctiva away fromthe implant.

Postoperative management

The operated eye only was padded, and patientswere mobilised the following day in spite of thepresence of a hyphaema in every case.

Local medication consisted of gutt. atropin. 1%,gutt. adrenaline tartrate 2%, and gutt. dexamethason.0I1% all given 3 times a day for 6 weeks, after

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Fig. 3 The implant has beensutured to sclera and the siliconetube laid across the eye so as tocut off the end, 2 mm insidethe limbus

which atropine and dexamethasone were stoppedwhile adrenaline tartrate was continued in twicedaily dosage until the intraocular pressure fell below15 mmHg.

All patients received a combination of a steroid,fluphenamic acid, and colchicine to control inflam-mation and limit fibrosis round the implant. Asmany of these patients were unable to tolerate largedoses of systemic steroids and others had severelyreduced renal function, our usual regimen ofprednisone 10 mg t.i.d., fluphenamic acid 200 mgt.i.d., and colchicine 0-25 to 0-5 mg t.i.d. for 6 weeks

was modified where necessary by replacing systemicsteroids by a weekly subconjunctival injection of0-25 ml of methylprednisolone and adjusting thedose of fluphenamic acid and colchicine accordingto renal function.

Postoperative behaviour of intraocular pressure

After insertion of an implant the eyes remained softfor up to 3 weeks, after which the intraocularpressures rose gradually to a peak of between 35and 60 mmHg (6 to 9 weeks after operation) and

Fig. 4 Eye of Patient 8, 7months after operation, showingbroad iridectomy and distendedbleb over implant (intraocularpressure 15 mmHg on adrenalinetartrate 2% b.d.)

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A. C. B. Molteno, M. M. B. Van Rooyen, and R. S. Bartholomew

Table 1 Effect of implants on IOP

Present/finalPatient Sex Age Preop. IOP IOP Treatment Follow-up Rentarks

(months)

1 Male 45 60 10-30 E 38 Late bleb thickeningSecond implant after 24 monthsRecurrent vitreous haemorrhage

2 Male 54 64 30 E 16 Iris blocked tubeSecond implant after 3 monthsPersistent low-grade iritis

3 Male 82 45 10 16 Eye quiet

4 Male 72 55 30 E 14 Eye quiet

5 Female 55 53 15 14 6/12 visionEye quiet

6 Female 70 42 5 10 Bleb perforationImplant removed after 8 monthsPoor general state due to rheumatoid arthritis

7 Female 68 67 12 E 8 Eye quietDied at 8 monthsUraemia and diabetes

8 Female 58 75 15 E 9 Eye quiet

9 Female 42 50 18 E 9 No rubeosisEye quiet

10 Male 70 30 E A 9 Eye quiet

11 Male 48 80 20 E 8 Ectropion uveaEye quiet

12 Female 55 52 17 E A S 6 Eye quiet

E=Epitrate (adrenaline tartrate). A Atropine. S=Sofradex (framycetin, dexamethasone, and gramicidin)

then fell rapidly at first and then more gradually toa stable value some 3 to 6 months after operation.The 'stable stage' pressures of 11 eyes with implantsare between 10 and 20 mmHg in 6 eyes and between20 and 30 mmHg in 5 eyes, while follow-up variesfrom 6 months to 38 months (Table 1).

Visual results

The visual acuity improved from 3/60 to 6/12 inone patient whose central vein occlusion wasprecipitated by chronic angle closure glaucoma.However, in the remaining cases, although measur-able improvement did not occur, all patients butone have retained their preoperative vision so far.

Behaviour of iris neovascularisation

The abnormal neovascular formations on the irispersisted as long as the intraocular pressure waselevated, but once it fell towards normal values (below35 mmHg) the vessels collapsed and became veryinconspicuous. However, they did not disappear, forwhere the intraocular pressure again became elevated

or if the anterior chamber became active (Table 1)they filled with blood and became obvious oncemore. I

Early complications

The postoperative course of these eyes was character-ised by a hyphaema in every case ranging from asmall collection of blood that took 6 days to clearto a full hyphaema which took 3 weeks to clear.The presence of blood in these cases did not alterthe treatment in any way and was not associatedwith severe pain or elevation of pressure.A more serious complication was iris blocking

the drainage tube. This occurred in 3 of the earliercases and was cleared surgically in 1 while in theremaining 2 cases a second implant was inserted.

Late complications

In 1 patient with severe rheumatoid arthritis andabnormally fragile tissue the anterior chamberremained very shallow with hypotony for 8 months,after which the implant became partially exposed

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by breakdown of the overlying conjunctiva and wasremoved. The only other late complication has beena late rise in pressure associated with recurrentmassive vitreous haemorrhages. This occurred 2years after insertion of the initial implant and wastreated by insertion of a second implant, which hasgiven reasonable control of pressure up to the timeof writing (14 months).Our results can be summed up by the statement

that after 14 operations carried out on 12 eyes withneovascular glaucoma all 12 eyes are pain-free andhave a pressure of less than 30 mmHg without anysystemic hypotensive medication.

Discussion

The use of implants to treat thombotic glaucoma isthe culmination of a long series of animal experi-ments and clinical investigations, during which theimplant technique has been extended to treatincreasingly severe and complex cases of glaucoma sothat a series of more than 330 operations with upto 10 years' follow-up is available for study. Inspite of this experience the authors have found thetreatment of neovascular glaucoma a difficult anddemanding field, because, in general, the patient'sstate is poor, the use of steroids, fluphenamic acid,and colchicine is essential for control of blebfibrosis, and the postoperative behaviour of theseeyes is stormy. However, the ultimate results aresurprisingly good, and even better results will beobtained in future now that the need for a broadiridectomy to remove iris from the vicinity of thetube is recognised. Many more cases are needed toassess the risks of sympathetic ophthalmitis and todecide the ultimate visual prognosis of these eyes.

However, at present we consider that insertion ofan implant with pharmacological control of blebfibrosis is the treatment of choice for neovascularglaucoma in only eyes, in cases with bilateral pre-disposing disease, and where significant vision ispresent in the glaucomatous eye.

The authors thank the Herbert Goosen Trust forfinancial support.

References

Blumenthal, M., Harris, L. S., and Galin, M. A. (1970).British Journal of Ophthalmology, 54, 62.

Ellis, R. A. (1960). American Journal of Ophthalmology, 50,733.

Epstein, E. (1959). British Journal of Ophthalmt7ology, 43, 641.MacDonald, R. K., and Pierce, H. F. (1965). AmzericanJournal of Ophthalmology, 59, 635.

Laplace, P. S. (1807). Traite de me'canique ce'leste (Supplementau xe livre), i.e., Supplement a la theorie de l'actioncapillaire. Paris, Courcier.

Martin, J. P., and Zorab, E. C. (1974). British Jourmial ofOphthalmology, 58, 536.

Molteno, A. C. B. (1969a). British Jouirnal of Ophthalmology,53, 161.

Molteno, A. C. B. (1969b). British Journal of Ophthalmology,53, 606.

Molteno, A. C. B. (1971). British Journal of Ophthalmology,55, 28.

Molteno, A. C. B. (1973a). South African Archives ofOphthal-mology, 1, 55.

Molteno, A. C. B. (1973b). South African Archives ofOphthal-mology, 1, 125.

Molteno, A. C. B., Straughan, J., and Ancker, E. (1976a).South African Medical Journal, 50, 881.

Molteno, A. C. B., Straughan, J., and Ancker, E. (1976b).South African Medical Journal, 50, 1062.

Young, T. (1805). Philosophical Transactions of the RoyalSociety of London, 95, 65.

Zorab, A. (1912). Transactions of the OphthalmologicalSocieti' of the United Kingdom, 32, 217.

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