Glaucoma Surgery

Educational Objectives

The goal of this program is to improve the management of glaucoma. After hearing and assimilating this program, the participant will be better able to:

1.   Compare and contrast the safety and efficacy of tube shunts to trabeculectomy for surgical treatment of glau­coma.

2.   Describe the effects of various levels of reduction of intraocular pressure on the rate of progression to glau­coma and set appropriate target pressures.

3.   Recognize the risk factors for progression to glaucoma.

4.   Describe the advantages of selective laser trabeculoplasty.

5.   Apply techniques that reduce the rates of complications and poor outcomes after trabeculectomy.

Faculty Disclosure

In adherence to ACCME Standards for Commercial Support, Audio-Digest requires all faculty and members of the plan­ning committee to disclose relevant financial relationships within the past 12 months that might create any personal con­flicts of interest. Any identified conflicts were resolved to ensure that this educational activity promotes quality in health care and not a proprietary business or commercial interest. For this program, the faculty and the planning committee re­ported nothing to disclose.

Acknowledgements

Dr. Gedde was recorded at New Horizons in Ophthalmology, held March 28-30, 2009, in Vail, CO, and sponsored by the Bascom Palmer Eye Institute of the University of Miami Health System, Miami, FL. Dr. Quigley spoke at Oph­thalmology 2008, held December 12-13, 2008, in San Francisco, CA, and presented by the University of California, San Francisco, Beckman Vision Center, Department of Ophthalmology. The Audio-Digest Foundation thanks the speakers and the sponsors for their cooperation in the production of this program.

Tube Shunt Surgery vs Trabeculectomy: 3-Year Results of TVT Study

Steven J. Gedde, MD, Professor of Ophthalmology, University of Miami, Bascom Palmer Eye Institute, Miami, FL

Trends in glaucoma surgery: numbers of trabeculectomies declined and tube shunts increased »3-fold between 1995 and 2004; optimal procedure for patients with previous ocular surgery remains unclear

Tube vs Trabeculectomy (TVT) Study

Criteria: inclusion  —  18 to 85 yr of age, intraocular pressure (IOP) ³18 mm Hg and £40 mm Hg, previous ocular surgery; exclusion  —  secondary glaucoma (eg, neovascular or uveitic), conjunctival scarring, need for other ocular surgeries

Tube group: 350-mm Baerveldt implant placed superotemporally with complete restriction of flow

Trabeculectomy group: patients underwent superior trabeculectomy with 0.4 mg/mL mitomycin C (MMC) for 4 min

Outcome measures: failure  —  IOP >21 mm Hg or reduced by <20% or £5 mm Hg at 2 consecutive visits after 3 mo; additional glaucoma surgery needed; loss of light perception; qualified success  —  supplemental medical therapy re­quired; complete success  —  no supplemental medical therapy

Baseline characteristics: 212 patients; mean IOP »25 mm Hg, with average of 3 medications; most had primary open angle glaucoma (POAG); average mean deviation -16 decibels; no significant differences between groups

Outcomes: trabeculectomy group had lower IOPs during first 3 mo, but not at ³6 mo; tube group used more adjunc­tive medical therapies during first 2 yr, but not at 3 yr; tube group had lower rate of failure (18% vs 34%); no differ­ence in rate of complete success; tube group had lower cumulative probability of failure at 3 yr (15.1% vs 30.7%)

Post hoc analysis: trabeculectomy group still had higher rate of failure if defined as IOP >17 mm Hg, or even >14 mm Hg

Reasons for failure: inadequate reduction of IOP (both groups); persistent hypotony; one patient had loss of light perception; no difference in distribution of reasons; reoperation  —  6 patients in tube group and 12 in trabeculec­tomy group had reoperations for glaucoma; of these, »50% in tube group received second tube shunt and »50% had cyclodestructive procedures; patients who failed in trabeculectomy group received Baerveldt tubes; one patient in each group had second reoperation (cyclodestructive procedure)

Early (first month) postoperative complications: most transient and self-limited (eg, choroidal effusions, shallow anterior chamber); trabeculectomy group had more wound leaks and early complications

Late postoperative complications: dysesthesia and bleb leaks more frequent in trabeculectomy group; number of patients with late complications similar between groups

Serious complications: number requiring reoperation or loss of ³2 Snellen lines of visual acuity (VA) similar be­tween groups; 3 patients in both groups had penetrating keratoplasty for persistent corneal edema; 6 in tube group had pars plana vitrectomy (2 for vitreous obstruction, 2 for aqueous misdirection, 1 for endophthalmitis, and 1 for retinal detachment); 4 had revision of Baerveldt with patch graft; 3 in trabeculectomy group had bleb revisions (2 for bleb leaks and 1 for hypotony maculopathy); some patients had drainage of choroidal effusions and one had drainage of suprachoroidal hemorrhage; no significant difference in rate of reoperation between groups

Visual acuity: Early Treatment Diabetic Retinopathy Study (ETDRS) and Snellen VA similar between groups; no significant difference in rate of loss of ³2 Snellen lines; reasons for loss of VA  —  glaucoma, macular disease, and reasons unrelated to procedures, eg, anterior ischemic optic neuropathy, diabetic retinopathy, and central retinal vein occlusion (CRVO)

Cataract progression: 24 patients in tube and 21 in trabeculectomy group had phakic eyes at enrollment; no differ­ence in rates of progression or cataract surgery between groups

Pearls and Myths From Clinical Trials in Glaucoma

Dr. Gedde

Pearl 1

Lowering IOP by ³30% delays or prevents worsening of glaucoma in patients with OAG

Collaborative Initial Glaucoma Treatment Study (CIGTS): found both medication and surgery effective in reduc­ing IOP, but reductions greater in surgery arm; both groups had stable visual field (VF) scores during 5-yr trial

Collaborative Normal Tension Glaucoma Study (CNTGS): treated patients whose IOP decreased by 30% had lower rate of progression than those in observation arm; effect of higher rate of cataracts in treatment arm masked full benefit

Advanced Glaucoma Intervention Study (AIGS): post hoc analysis  —  patients who maintained IOP <18 mm Hg on every visit had no progression of VF loss (mean IOP 12.3 mm Hg); greater rates of progression observed in pa­tients with shorter periods in which IOP <18 mm Hg  

Early Manifest Glaucoma Treatment Trial (EMGT): lowering IOP by <30% resulted in greater rates of progres­sion of glaucoma; patients in treatment group with average reduction in IOP of 25% had relatively rapid rate of pro­gression

Myth 1

All patients must have IOP <18 mm Hg at each visit or average IOP 12.3 mm Hg to prevent progression; however, pa­tients in AGIS had average IOP of 26 mm Hg, therefore reduction to £17 mm Hg represented 35% change

Pearl 2

Lowering IOP by 20% in patients with ocular hypertension (OHT) reduces risk of developing POAG by 50%

Ocular Hypertension Treatment Study (OHTS): compared rate of conversion from OHT to glaucoma in observa­tion arm to arm receiving topical medication that lowered IOP by 20%, to £24 mm Hg; conversion rate higher in observation arm

Pearl 3

Important to repeat VF evaluations; OHTS found glaucomatous abnormalities confirmed in only 14% of patients after retest of VF; CNTGS also found high rate of false-positive results from single confirmatory VF test

Myth 2

Diabetes protects patients with OHT from developing glaucoma

OHTS: factors predictive of progression included older age, higher IOP, larger cup-to-disc ratios, higher pattern stan­dard deviation, and thinner central corneal thicknesses; patients with self-reported diabetes appeared at lower risk; however, patients with diabetic retinopathy excluded; several epidemiologic studies show diabetes either weak risk factor or not risk factor for glaucoma, but not protective

European Glaucoma Prevention Study (EGPS): protective effect of diabetes disappeared when data pooled with those of OHTS

Target IOP: speaker aims to lower IOP by 20% for patients with OHT, by 30% for patients with mild glaucoma (de­termined by VF), by 40% for moderate glaucoma, and by 50% or to £15 mm Hg for severe glaucoma

Selective Laser Trabeculoplasty

Dr. Gedde

Advantages of laser trabeculoplasty: argon laser trabeculoplasty (ALT) and selective laser trabeculoplasty (SLT) effective in most patients with OAG and not dependent on patient compliance

Differences: argon laser used for ALT and frequency-doubled yttrium aluminum garnet (YAG) laser for SLT; spot size larger and duration  of irradiation shorter in SLT; energy levels differ; spot size  —  in ALT, 50-mm spot focused at junction between pigmented and nonpigmented trabecular meshwork (TM); SLT produces 400-mm spot span­ning TM; ALT  —  improves aqueous outflow and alters extracellular matrix and glycosaminoglycans; SLT  —  uses selective photothermolysis (selectively targets pigmented TM cells); generates confined heat with short pulse; does not cause coagulative necrosis and damage to adjacent tissue; both ALT and SLT stimulate division and migration of trabecular endothelial cells

Autopsy study: better preservation of normal architecture of TM after SLT

Outcomes: ALT  —  produces 65% to 95% rate of initial success, with 20% to 30% reduction in IOP; effect deterio­rates by 5% to 10% per year; after 5 yr, benefit persists in only »50% of patients; SLT  —  »80% rate of response, with 20% to 30% reduction of IOP; comparison studies show no difference in reduction of IOP or loss of effect over time

Retreatment: ALT had lower rate of success for repeat treatment, and IOP may even rise after retreatment; rate of success with repeat SLT similar to initial SLT; SLT had significant benefit over ALT in eyes previously treated with ALT

Indications: inadequately controlled IOP despite maximum tolerated medical therapy; patients who comply poorly with medical therapy; considered appropriate as initial therapy

Laser trabeculoplasty as initial therapy: Glaucoma Laser Trial (GLT)¾ one eye treated with 360° of ALT and oth­ereye treated with stepped medical regimen beginning with timolol; better control of IOP in ALT eyes; study of SLT as primary therapy  —  showed 30% reduction of IOP in patients treated initially with SLT

How to Stay Out of Trouble Doing Trabeculectomy

Harry A. Quigley, MD, A. Edward Maumenee Professor of Ophthalmology, Johns Hopkins University School of Medicine, and Director, Dana Center for Preventive Ophthalmology, Wilmer Eye Institute, Johns Hopkins Uni­versity, Baltimore, MD

Trabeculectomy blebs: presence of microcysts similar to guttata indicates adequate water percolating through con­junctiva; poor blebs symptomatic and can lead to dellen

Recommendations: center trabeculectomies just off 12 o’clock; fornix-based flaps preferred (fewer bleb symptoms, leaks, and infections); dissect posteriorly (almost to orbital septum); speaker uses antifibrosis only in patients with previous failed filters or in whom fellow eye failed, in young patients with secondary glaucoma, and in those who need low target IOP (ie, about 70% of speaker’s patients)

Mitomycin C (MMC): apply under conjunctiva with cut piece of Wexel sponge; MMC increases likelihood of thin and leaky blebs and hypotony (trade-off situation)

Technique: aim to close scleral flap to make it almost water-tight; insert paracentesis track; enter chamber; make one Kelly punch bite in center, leaving ledge on both sides so flap tamponades hole; full-thickness procedure if opened all way across; speaker uses iridotomy (previously did not use in pseudophakic filters, but saw 2% rate of iris clos­ing hole); place flap back down and iris into center; check for positive pressure to determine whether >3 sutures needed in scleral flap (eyes with angle closure and small eyes more likely to have iris and lens come out because of choroidal expansion); place sutures with slip knots; reform chamber and check for leakage; if none, loosen slip knot; if too much leakage, tighten knots; if 3 insufficient, place 5, 7, or 9 sutures; make one knot tight, one medium, and one loose; aim tight suture toward 12 o’clock position to give direct aqueous flow; push to verify iris not in hole and no blood clot present

Suture lysis: technique  —  press down gently with lens; cut suture directed at 12 o’clock, where it enters sclera; push to make sure bleb pops up; if it does not and pressure remains too high, cut second suture; use spot parameters of 0.1 sec, 50 mm, 500 mWatt; avoid lysis on first day; if IOP very high, perform gonioscopy on first day to look for clot in hole; disadvantages  —  requires laser; if blood under conjunctiva blocks view, use krypton laser; advantages  —  3 sutures allow flexible control of IOP; not necessary to remove sutures

Low IOP after trabeculectomy: causes  —  overfiltration, inflammatory hyposecretion, bleb leaks, cyclodialysis (rare), cross-over effect of medication from fellow eye or systemic beta-blockers, retinal detachment, or carotid insufficiency; Seidel test  —  use fluorescein drops rather than strips; symptoms include metamorphopsia, unclear vision, and decompression hemorrhage accompanying sudden loss of IOP

Treatment: Place shield on eye and limit physical activity; bleb leaks may heal spontaneously; otherwise, surgically remove leaking area and advance conjunctiva forward by dissecting into fornix and attaching to limbus; for large, painful blebs, remove that part of conjunctiva; speaker does 5% rate of trabeculectomy revision for control of IOP; 70% of patients improve after removing part of bleb; to perform bleb repair, remove conjunctiva and ad­vance conjunctiva from fornix, place small nick in cornea, insert 10-0 Vicryl as mattress suture into slit in cornea, take out through conjunctival flap once, back through flap again, up through cornea, up through slit, and tie 2=1=1 surgeon’s knot; pull two single wing 10-0 polyglactin 10 sutures to tighten across limbus

Blebitis: long-term risk (1 per 1,500 per year follow-up); risk factors include use of MMC, history of bleb leak, long-term use of chronic antibiotics on patients with blebs, and contact lenses; treatment  —  for blepharitis, use local lid hygiene ; tobramycin and dexamethasone (TobraDex) not recommended; for red eye with no pus or anterior cham­ber cells, observe without treatment or use topical fluoroquinolone every 6 hr; if aqueous cells present, treat with fluoroquinolone (eye drops every hour and orally), and examine daily; if vitreous inflammation present, inject anti­biotics into eye hourly and consider hospitalization

Hemorrhagic choroidal detachment: may occur intraoperatively or at any time postoperatively (usually early); if eye phakic, chamber shallow or flat; lower IOP immediately and delay drainage for 5 days; rate of complex retinal detachment high because of evulsion of vitreous base and retinal base; prognosis guarded; if patient has had this in first eye, preplace 10-0 nylon sutures on scleral flap, fill chamber with viscoelastic (eg, Healon), enter, punch, per­form iridectomy, and close within 30 sec to minimize choroidal expansion

Suggested Reading

Feldman RM, Tabet RR: Needle revision of filtering blebs. J Glaucoma 17:594, 2008; Gedde SJ et al: Three-year follow-up of the tube vs trabeculectomy study. Am J Ophthalmol Aug 10, 2009 [Epub ahead of print]; Hau S, Barton K: Corneal com­plications of glaucoma surgery. Curr Opin Ophthalmology 20:126, 2009; Hong BK et al: Repeat selective laser trabeculo­plasty. J Glaucoma 18:180, 2009; Law SK et al: Long-term outcomes of repeat vs initial trabeculectomy in open-angle glaucoma. Am J Ophthalmol Jul 9, 2009 [Epub ahead of print]; Murthy S, Latina MA: Pathophysiology of selective laser tra­beculoplasty. Int Ophthalmol Clin 49:89, 2009; Nguyen QH: Primary surgical management refractory glaucoma: tubes as ini­tial surgery. Curr Opin Ophthalmol 20:122, 2009; Palanca-Capistrano AM et al: Long-term outcomes of intraoperative 5-fluorouracil versus intraoperative mitomycin C in primary trabeculectomy surgery. Ophthalmology 116:185, 2009; Radh­krishnan S et al: Outcomes of surgical bleb revision for complications of trabeculectomy. Ophthalmology Jul 28, 2009 [Epub ahead of print]; Rauscher FM et al: Motility disturbances in the tube versus trabeculectomy study during the first year of fol­low-up. Am J Ophthalmol 147:458, 2009; Realini T: Selective laser trabeculoplasty: a review. J Glaucoma 17:497, 2008; Sarkisian SR Jr: Tube shunt complications and their prevention. Curr Opin Ophthalmol 20:126, 2009; Singh K, Shrivastava A: Early aggressive intraocular pressure lowering, target intraocular pressure, and a novel concept for glaucoma care. Surv Ophthalmol 53 (Suppl 1):S33, 2008; Singh M et al: Utility of bleb imaging with anterior segment optical coherence tomogra­phy in clinical decision-making after trabeculectomy. J Glaucoma 18:492, 2009.