Glaucoma Symposium

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.   Summarize the data supporting early detection and treatment of glaucoma.

2.   Compare the performance of short-wavelength and standard automated perimetry in early detection of glau­coma.

3.   Recognize the risk factors for progression to glaucoma.

4.   Determine which form of surgical intervention is appropriate for individual patients with glaucoma.

5.   Evaluate the advisability of operating a motor vehicle for glaucoma patients on the basis of their degree of vi­sual impairment.

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, Dr. Skuta reported serving as a consultant and speaker for Alcon. He also presents information in his lecture that is related to off-label or investigational use of a therapy, product, or device. Drs. Burney and Callender and the planning committee reported nothing to disclose.

Acknowledgements

Dr. Skuta was recorded at the 32nd Annual UC Davis Ophthalmology Symposium, Pressing Issues in Ophthalmology, held May 15-17, 2009, in Napa, CA, and sponsored by the UC Davis Health System Office of Continuing Medical Education and the Eye Center, Davis, CA. Drs. Burney and Callender spoke at the 27th Annual Meeting: Update for the Comprehen­sive Ophthalmologist 2009, held April 24, 2009, in Cleveland, OH, and presented by the University Hospitals, Case Medi­cal Center, and Case Western Reserve University School of Medicine, Cleveland, OH. The Audio-Digest Foundation thanks the speakers and the sponsors for their cooperation in the production of this program.

Early Gluaucoma Detection: So What?

Gregory L. Skuta, MD, James P. Luton Clinical Professor, Dean A. McGee Eye Institute, Department of Oph­thalmology, University of Oklahoma, Oklahoma City

Preperimetric glaucoma: 30% to 40% of retinal ganglion cells lost before structural loss detected in optic disc and retinal nerve fiber layer; functional damage not detected by standard automated perimetry (SAP) until 25% to 35% localized loss of retinal ganglion cells has occurred

New technologies: optical coherence tomography (OCT), GDx Nerve Fiber Layer Analyzer, and Heidelberg Retinal Tomography (HRT)

Ocular Hypertension Treatment Study (OHTS): confocal laser scanning ophthalmology (CSLO) ancillary study results  —baseline topographic characteristics of optic disc associated with development of primary open angle glaucoma (POAG); positive predictive values of CSLO indices ranged from 14% to 40%; OHTS results  —  changes in optic nerve appeared before of loss of visual field (VF) detected by SAP; risk factors for progression included higher vertical and horizontal cup-to-disc ratios and higher pattern standard deviations; 56% of end points involved optic nerve; assessment of risk important

Short-wavelength automated perimetry (SWAP): blue-on-yellow perimetry may detect damage 3 to 5 yr earlier than SAP; blue-on-yellow used to reduce overlap between receptors; reported to have greater sensitivity and may detect progression earlier; affected more by age and cataracts; has greater range of normality and long-term vari­ability; Swedish interactive threshold algorithms (SITA)-SWAP now available; reduces testing time to 4 to 6 min

Study results: among 450 patients with ocular hypertension (OH), 23 showed conversion to POAG on SAP, but 20 of these did not show earlier conversion on SWAP; in 3 of 23, SWAP showed conversion £18 mo earlier; in 4 of 23, SAP showed earlier conversion, so superiority of SWAP unclear

Early treatment

OHTS results: rate of progression to glaucoma at 5 yr, 4.4% in patients who received medication, vs 9.5% in obser­vation group; more aggressive therapy and lower target intraocular pressures (IOPs) perhaps necessary for patients with detectable damage; OHTS II  —  examining effect of delay in treatment on likelihood of progression

Collaborative Initial Glaucoma Treatment Study (CIGTS): patients randomized to initial treatment with medica­tion or surgery; IOPs 35% to 45% lower in medication arm and ³45% lower in surgery arm; VF scores similar at 5 yr; stratified analysis  —  patients with minimal loss of VF at baseline (mean deviation, -2) responded similarly to medication and surgery; patients in medication arm with mean deviations of ³-10 more likely to progress over 7 to 8 yr than those in surgery arm; greatest degree of progression overall (mean deviation, ³3) occurred in medication arm

Effect of life expectancy: delayed treatment may result in greater lifetime chance for visual impairment because of increasing life expectancy

Cost-effectiveness (OHTS results): treating everyone with OH estimated to cost $4 billion per year; cost-effective to treat patients with IOP ³24 mm Hg and ³2% annual (10% per 5 yr) risk for POAG; appropriate treatment threshold risk of 10% to 15% over 5 yr

Glaucoma risk calculators: based on results of OHTS and European Glaucoma Prevention Study; allow estimate of 5-yr risk of developing glaucoma in ³1 eye

Glaucoma Surgery 2009: Where Are We Now and Can We Do Better?

Dr. Skuta

Risk factors: family history  —  OHTS found self-reported family history of POAG insignificant predictive factor; 8.5% of participants with family history developed POAG compared to 7.3% who did not; 42% of participants re­ported family history of glaucoma; speaker still considers family history in making treatment decisions; black ethnicity  —  apparent predictive factor in univariate but not multivariate analyses

Trabeculectomy: gold standard; success rates high, especially if antifibrotic agents used; can titrate flow with laser suture lysis and releasable sutures; creates diffuse, ischemic but not avascular filtering bleb; indications  —  documented progression despite medical therapy with or without laser surgery or anticipated damage based on IOP; data from CIGTS showed earlier surgical intervention appropriate for patients with advanced damage

Wound healing: higher success rates achieved with 5-fluorouracil (5-FU) in high-risk eyes during filtering surgery and primary trabeculectomies; study of mitomycin vs 5-FU in high-risk eyes showed similar overall rates of suc­cess, but lower pressures achieved with mitomycin at 6 and 32 mo; in primary trabeculectomies, outcomes simi­lar (ie, decreased IOP, minimal hypotony maculopathy with both); slightly higher proportion of patients receiving mitomycin achieved lower IOP goals

American Glaucoma Society Survey 2002: use of mitomycin increasing in primary trabeculectomy (68%) and combined cataract glaucoma filtering surgery (83%)

Inferior trabeculectomy: no longer performed because of 7-fold greater risk for infection compared to superior tra­beculectomy

Hypotony maculopathy: risk factors include young age (average 50 yr), myopia (refractive error »-3), and male sex (similar to risk factors for pigmentary glaucoma); these individuals had lower risk for choroidal effusion

Complications of antifibrotic therapy: hypotony, wound and bleb leaks, and infection, including endophthalmitis; resulted in increased use of tubes vs trabeculectomy, except in patients with previous phacoemulsification, in whom 95% to 96% of clinicians still use trabeculectomy

Surgical Innovations

Deep sclerectomy: collagen implant placed in nonpenetrating window to achieve flow through Descemet’s window; studies show trabeculectomy generally achieves lower IOPs

Tubes and shunting devices: Tube Versus Trabeculectomy (TVT) study randomized patients with uncontrolled glau­coma after previous trabeculectomy, cataract surgery, or both to Baerveldt 350-mm² implants or trabeculectomy with mitomycin; patients had baseline mean IOPs in mid 20s (mm Hg) and significant loss of VF (mean deviations of -16); patients in trabeculectomy arm had lower IOPs at 1 mo; by 1 yr, groups had similar IOPs; patients in tube arm required more medication; trabeculectomy arm had higher overall rates of failure as well asmore complete successes (no medication required); failures due to hypotony (more common after trabeculectomy)

Serious complications: similar but trending toward more visual loss at 1 yr in trabeculectomy arm; at 3 yr, IOPs and number of medications needed similar (1.3 medications for tube arm 1.0 for trabeculectomy arm); rate of failure remained higher in trabeculectomy arm because of inadequate control of IOP and persistent hypotony; visual outcomes similar (loss of ³2 Snellen lines) P=0.92; early surgical complications more common with trabeculec­tomy; similar rates of late and serious complications

Other options: cyclophotocoagulation  —  study of 92 patients receiving primary diode laser cyclophotocoagulation showed modest decrease in IOPs (only 67% had decline, and only 47% achieved decline of ³20%); final IOP of <22 mm Hg achieved in only 48%; atonic pupils found in 25% of eyes; Ex-Press shunts  —  previously, insertion un­der conjunctiva without placement under scleral flap unsuccessful because of erosions, hypotony, and flat cham­bers; placement beneath scleral flap causes less hypotony and choroidal effusions, compared to trabeculectomy; eye stent and Eyepass glaucoma implant  —modest reductions of IOP from mid to high 20s (mm Hg) to mid to high teens; canalplasty  —  dilates canal of Schlemm to rejuvenate outflow system; IOPs dropped from mid 20s (mm Hg) to mid teens in one study, with 70% to 80% rate of success; Trabectome  —  creates trabeculotomy ab interno; ab­lates overlying trabecular meshwork in canal of Schlemm; achieves pressures in mid teens

Gluaucoma Shunts

Edward N. Burney, MD, Professor, Department of Ophthalmology and Visual Sciences, Case Western Reserve University/University Hospitals of Cleveland, and Director of Ophthalmology, Cleveland Veterans Affairs Med­ical Center, Cleveland, OH

Refractory glaucoma: studies suggest shunts or tube devices give better control of IOP for patients with this condi­tion

Blebs: histologic data show similar blebs created by trabeculectomy and tube shunts; aqueous from eyes with glau­coma contains inflammatory factors that promote healing or excessive formation of scar tissue; to promote forma­tion of good blebs, protect eye from excessive inflammation (eg, use of diclofenac recommended when adjunct agent, such as mitomycin, not used) and reduce exposure of bleb to aqueous

Device types: single- or double-plated with or without valves; presence or absence of valve and size of reservoir main criteria for selection of implant

Valves: valved implants  —  in Ahmed, Krupin, and Molteno-3, valves set to vent at IOP of 8 to 11 mm Hg to reduce hypo-tony; increases risk for obstruction; nonvalved  —  vent to equilibrium; produce more hypotony but less ob­struction; recommendation  —  use valved implant or ligating suture  

Reservoir size: 2 studies found higher incidence of diplopia with double plates; recommendation  —  use single plate device for similar range of IOP with less chance of diplopia

Ex-press mini shunt: 3 mm stainless steel tube with external diameter of 400 µ and internal diameter of 50 or 200 µ; preloaded; study of 50 eyes showed IOP reduced from 27 to 14 mm Hg

Molteno-3: more flexible, with lower-profile plate; in corneal transplants, elevation can occur close to limbus, with trabeculectomy causing lifting of lid and formation of dellens in front of bleb; tubes allow placement of plate more posteriorly; comparison of 44 Molteno-3 vs 44 Molteno double-plated devices found no difference in re­duction of IOP

Procedure: create limbal-based flap, dissect posteriorly, and anchor device; place plate ³8 to 10 mm from limbus; during paracentesis for tube, penetrate 1 to 2 mm from limbus, and pass into anterior chamber, pointing away from ciliary body and iris, but not too close to cornea; use cover (eg, freeze-dried pericardium) to minimize erosion

Procedure for Ex-press mini shunt: dissect, apply mitomycin, punch with 25 gauge or 27 gauge needle, insert de­vice at angle of »30° to avoid vaulting of posterior portion of implant, and stitch; speaker does not find checking flow predictive

Complications: intraoperative  —  placement too far anteriorly or not far enough posteriorly can cause tear film ab­normalities; if placed at inappropriate angle, tube can interfere with endothelium and cause localized corneal edema; postoperative  —exposure of tube occurs most often in patients with dry eye; extrusion may occur more of­ten if tube placed above Tenon’s fascia under conjunctiva; speaker recommends against using enhancement agent if tube placed under conjunctiva alone, but consider using agent if tube placed under Tenon’s fascia; failure  —  defined by many parameters; inadequate control of IOP; cyst formation and encasement (may use 30-gauge needle to per­forate cyst); infection (rare because of posterior position); hemorrhage (rare); extrusion and erosion (common); diplopia (more common in patients with double-plated implants)

Tube shunts vs trabeculectomy: study compared 105 trabeculectomies with mitomycin to 107 tubes in patients with refractory glaucoma; found trabeculectomies produced lower pressure early, but had more long-term complications and failures; concluded tube shunts more effective in these patients

Postoperative management: use of agents to suppress inflammation recommended; aqueous suppressants more ben­eficial than aqueous outflow agents to reduce pressure in early phases

Should This Glaucoma Patient Be Driving?

Odette V. Callender, MD, Assistant Professor, School of Medicine, University of Maryland, and Chief of Oph­thalmology, Veterans Affairs Medical Center, Wilmington, DE

Association of accidents with glaucoma: elderly population performed more poorly in traffic and driving simulator tests; multiple studies show glaucoma associated with increased risk for accidents in traffic or driving simulators; failure to yield to pedestrians most common problem; one study reported no increased association with accidents, but noted that glaucoma patients tended to avoid driving under difficult conditions; severity of visual impairment unknown

Loss of VF: drivers with mean horizontal field diameter 84° ±35° had diminished ability to maintain lane position; patients with restricted VF (»123°) performed poorly in some driving tasks; patients with milder loss of VF (»130°) showed no impairment in driving skills

Driving avoidance: study showed avoidance not sufficient to prevent accidents

Assessing VF: Humphrey 24-2 test results not well correlated with driving performance; patients with <110° of total field or <100° in better eye (as determined by Goldmann test) more likely to have simulator accident

Other options: binocular Esterman test standard in United Kingdom; advanced glaucoma intervention scoring (AGIS) used in Humphrey test for worse eye; integrated VF (IVF) test still in research phase, agrees with Ester­man; useful field of view (UFOV) test  —  high sensitivity and specificity in predicting risk for automobile acci­dents, but not practical for widespread screening

Suggested Reading

Da Pozzo S et al: Scanning laser polarimetry – a review. Clin Experiment Ophthalmol 37:68, 2009; Fiscella RG et al: Cost of illness of glaucoma: a critical and systematic review. Pharmacoeconomics 27:189, 2009; Hau S, Barton K: Corneal complications of glaucoma surgery. Curr Opin Ophthalmol 20:131, 2009; Ivandic BT et al: Early diagnosis of ocular hy­pertension using a low-intensity laser irradiation test. Photomed Laser Surg Jun 10, 2009 [Epub ahead of print]; Lin AP et al: Management of chronic open-angle glaucoma in the aging US population. Geriatrics 64:20, 2009; Naka M et al: Com­parison of mean deviation with AGIS and CIGTS scores in association with structural parameters in glaucomatous eyes. J Glaucoma 18:379, 2009; Ng M et al: Comparing the gull-threshold and Swedish interactive thresholding algorithms for short-wavelength automated perimetry. Invest Ophthalmol Vis Sci 50:1726, 2009; Nguyen QH: Primary surgical manage­ment refractory glaucoma: tubes as initial surgery. Curr Opin Ophthalmol 20:122, 2009; Nomoto H et al: Detectability of glaucomatous changes using SAP, FDT, flicker perimetry, and OCT. J Glaucoma 18:165, 2009; Pagliara MM et al: The role of OCT in glaucoma management. Prog Brain Res 173:138, 2008; Ramulu PY et al: Driving cessation and driving limitation in glaucoma: the Salisbury eye evaluation project. Ophthalmology Jul 8, 2009 [Epub ahead of print]; Ramulu P: Glaucoma and disability: which tasks are affected, and at what stage of disease? Curr Opin Ophthalmol 20:92, 2009; 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; Sarkisian SR Jr: Tube shunt complications and their prevention. Curr Opin Ophthalmol 20:126, 2009; Schrems WA et al: Comparison of scanning laser polarimetry and optical coherence tomography in quanti­tative retinal nerve fiber assessment. J Glaucoma Apr 15, 2009 [Epub ahead of print]; Singh K, Shrivastava A: Early ag­gressive intraocular pressure lowering, target intraocular pressure and a novel concept for glaucoma care. Surv Ophthalmol 53 (Suppl1):S33, 2008; Sit AJ, Liu JH: Pathophysiology of glaucoma and continuous measurements of intraocular pres­sure. Mol Cell Biomech 6:57, 2009; Zhong Y et al: Blue-on-yellow perimetry and optical coherence tomography in patients with preperimetric glaucoma. Clin Experiment Ophthalmol 37:262, 2009.