Glaucoma Surgery in Resource-Poor Settings

From Kahook's Essentials Of Glaucoma Therapy
Primary authors
  • Nathan Congdon, MD, MPH

Glaucoma is the world’s leading cause of irreversible blindness, affect-ing an estimated 60.5 million persons and responsible for vision loss among 8.4 million in 2010.[1] This chapter deals with case identification and manage-ment of this condition in areas of limited resources.

Case Identification

Traditional screening tests—Goldmann tonometry, automated visual fields, and evaluation of the disc—are limited in their ability to detect glaucoma,[2][3] and there is little to suggest that newer devices[4][5][6][7] will improve screening performance soon. No trial evidence currently supports the benefit of screening for open-angle glaucoma (OAG)[8] or angle-closure glaucoma (ACG)[9], which may not be cost-effective in the developed[10][11][12][13] or developing[14][15] world. Case finding in the clinic is the best current strategy to detect glaucoma in areas of limited­ resources.[16]

Expense and poor accuracy among inexperienced patients[13][17] render field machines impractical in resource-poor areas. Examination of the optic nerve is better-suited to these settings and will likely identify patients at risk for blindness, the key target for case identification.

Primary angle-closure glaucoma has a greater risk of blindness com-pared with OAG[18] and definitely benefits from early treatment with peripheral iridectomy (PI).[19] Thus, routine assessment of the anterior chamber angle is important, particularly in areas with high angle-closure prevalence. Simpler tests, such as oblique illumination of the eye, lack diagnostic accuracy,[20][21] whereas slit-beam assessment of the peripheral angle[22] requires a slit lamp and is as resource-demanding as gonioscopy, although it may be quicker and require less training. Poor specificity limits newer imaging­ technologies,[9][23] which are not suited for use in poor areas. Gonioscopy appears to provide the best accuracy for modest resources in characterizing the angle.

Examination of the optic nerve and angle both presuppose significant training efforts in areas of limited resources. Few studies have examined the impact of training on accuracy in optic nerve assessment[24][25] or gonioscopy.[26]

Treatment

Medical therapy for glaucoma involves long-term use of therapies that may be expensive, difficult to obtain, and poorly tolerated, and is thus not well-suited for use in resource-poor areas. Glaucoma surgery may cause lens opacity[27] and vision loss[28] and is thus most appropriate for persons with vision-threatening disease.

Many patients at risk for glaucoma may also have concurrent cataract, and cataract extraction may be definitive therapy for those with ­narrow angles, angle closure, and possibly ACG. Trabeculectomy could be utilized for those with OAG and potentially advanced cases of ACG in which cataract extraction alone might not provide safe levels of pressure control. Few trials of glaucoma surgery have been carried out in the developing world,[29] but randomized trials in richer areas suggest generally equivalent safety and efficacy for strategies involving trabeculectomy, laser trabeculoplasty, and tube shunts.[28][30] Although laser devices are too expensive for resource-poor areas, the manufacture of high-quality, low-cost intraocular lenses (IOLs) in India and elsewhere provides a model for cheap seton devices. The recent Tube Versus Trabeculectomy Study (TVT)[28] and clinical experience suggest that tubes are at least as effective and safer than trabeculectomy, and may be more appropriate for less-experienced surgeons and more tolerant of limited follow-up and compliance with postoperative medications in poor settings.

Key points

  • A combination of clinic-based case detection and surgery for severely-affected cases may be the most appropriate and sustainable approach to combatting glaucoma blindness in resource-poor settings
  • While trabeculectomy and/or cataract surgery may be appropriate for many patients, as inexpensive, locally-produced tube shunts and potentially new devices for implantation into Schlemm’s canal become available, these may play an increasing role in surgical treatment.

References

  1. ↑ Quigley HA, Broman AT. The number of people with glaucoma worldwide in 2010 and 2020. Br J Ophthalmol. 2006;90:262-267.
  2. ↑ Stoutenbeek R, de Voogd S, Wolfs RC, et al. The additional yield of a periodic screening programme for open-angle glaucoma: a population-based comparison of incident glaucoma cases detected in regular ophthalmic care with cases detected during screening. Br J Ophthalmol. 2008;92:1222-1226.
  3. ↑ Tielsch JM, Katz J, Singh K, et al. A population-based evaluation of glaucoma screening: the Baltimore Eye Survey. Am J Epidemiol. 1991;134:1102-1110.
  4. ↑ Healey PR, Lee AJ, Aung T, et al. Diagnostic accuracy of the Heidelberg Retina Tomograph for Glaucoma: a population-based assessment. Ophthalmology. 2010;117: 1667-1673.
  5. ↑ Zheng Y, Wong TY, Lamoureux E, et al. Diagnostic ability of Heidelberg Retina tomography in detecting glaucoma in a population setting: the Singapore Malay Eye Study. Ophthalmology. 2010;117:290-297.
  6. ↑ Iwase A, Tomidokoro A, Araie M, et al. Performance of frequency-doubling technology perimetry in a population-based prevalence survey of glaucoma. The Tajimi Study. Ophthalmology. 2007;114:27-32.
  7. ↑ Wang YX, Xu L, Zhang RX, et al. Frequency-doubling threshold perimetry in predict-ing glaucoma in a population-based study: the Beijing Eye Study. Arch Ophthalmol. 2007;125:1402-1406.
  8. ↑ Hatt S, Wormald R, Burr J. Screening for prevention of optic nerve damage due to chronic open angle glaucoma. Cochrane Database Syst Rev. 2006:CD006129.
  9. ↑ 9.0 9.1 Yip JL, Foster PJ, Uranchimeg D, et al. Randomised controlled trial of screening and prophylactic treatment to prevent primary angle closure glaucoma. Br J Ophthalmol. 2010;94:1472-1477.
  10. ↑ Blanco A, Zangwill LM. Is there an appropriate, acceptable and reasonably accurate screening test? In: Weinreb R, Healey P, Topouzis F, eds. Glaucoma Screening: 5th Consensus Report World Glaucoma Association. Amsterdam, The Netherlands: Kugler; 2008:33-50.
  11. ↑ Burr JM, Mowatt G, Hernandez R, et al. The clinical effectiveness and cost-effectiveness of screening for open angle glaucoma: a systematic review and economic evaluation. Health Technol Assess. 2007;11:iii-iv, ix-x, 1-190.
  12. ↑ Mowatt G, Burr JM, Cook JA, et al. Screening tests for detecting open-angle glaucoma: systematic review and meta-analysis. Invest Ophthalmol Vis Sci. 2008;49:5373-5385.
  13. ↑ 13.0 13.1 Hirneiss C, Niedermaier A, Kernt M, et al. Health-economic aspects of glaucoma screening. Ophthalmologe. 2010;107:143-149.
  14. ↑ Thomas R, Sekhar GC, Parikh R. Primary angle closure glaucoma: a developing world perspective. Clin Exp Ophthalmol. 2007;35:374-378.
  15. ↑ Thomas R, Sekhar GC, Kumar RS. Glaucoma management in developing countries: medical, laser, and surgical options for glaucoma management in countries with limited resources. Curr Opin Ophthalmol. 2004;15:127-131.
  16. ↑ Maul EA, Jampel HD. Glaucoma screening in the real world. Ophthalmology. 2010;117:1665-1666.
  17. ↑ Iwase A, Tomidokoro A, Araie M, et al. Performance of frequency-doubling technology perimetry in a population-based prevalence survey of glaucoma. The Tajimi Study. Ophthalmology. 2007;114:27-32.
  18. ↑ Foster PJ, Johnson GJ. Glaucoma in China: how big is the problem? Br J Ophthalmol. 2001;85:1277-1282.
  19. ↑ Lam D, Tham C, Congdon N. Peripheral iridectomy for angle-closure glaucoma. In: Shaarawy TM, Hitchings RA, Crowston JG, eds. Glaucoma: Medical Diagnosis & Therapy. Vol 2. Philadelphia, PA: Saunders/Elsevier; 2009:61-70.
  20. ↑ He M, Huang W, Friedman DS, et al. Slit lamp-simulated oblique flashlight test in the detection of narrow angles in Chinese eyes: the Liwan eye study. Invest Ophthalmol Vis Sci. 2007;48:5459-5463.
  21. ↑ Thomas R, George T, Braganza A, et al. The flashlight test and van Herick’s test are poor predictors for occludable angles. Aust N Z J Ophthalmol. 1996;24:251-256.
  22. ↑ Nolan WP, Aung T, Machin D, et al. Detection of narrow angles and established angle closure in Chinese residents of Singapore: potential screening tests. Am J Ophthalmol. 2006;141:896-901.
  23. ↑ Lavanya R, Foster PJ, Sakata LM, et al. Screening for narrow angles in the singapore population: evaluation of new noncontact screening methods. Ophthalmology. 2008;115:1720-1727.
  24. ↑ Abrams LS, Scott IU, Spaeth GL, et al. Agreement among optometrists, ophthalmologists, and residents in evaluating the optic disc for glaucoma. Ophthalmology. 1994;101:1662-1667.
  25. ↑ Quigley HA, West SK, Munoz B, et al. Examination methods for glaucoma prevalence surveys. Arch Ophthalmol. 1993;111:1409-1415.
  26. ↑ Congdon NG, Spaeth GL, Augsburger J, et al. A proposed simple method for measurement in the anterior chamber angle: biometric gonioscopy. Ophthalmology. 1999;106:2161-2167.
  27. ↑ AGIS Investigators. The Advanced Glaucoma Intervention Study: 6. Effect of cataract on visual field and visual acuity. Arch Ophthalmol. 2000;118:1639-1652.
  28. ↑ 28.0 28.1 28.2 Gedde SJ, Schiffman JC, Feuer WJ, et al. Treatment outcomes in the tube versus trabeculectomy study after one year of follow-up. Am J Ophthalmol. 2007;143:9-22.
  29. ↑ Robin AL, Ramakrishnan R, Krishnadas R, et al. A long-term dose-response study of mitomycin in glaucoma filtration surgery. Arch Ophthalmol. 1997;115:969-974.
  30. ↑ AGIS Investigators. The Advanced Glaucoma Intervention Study: 7. The relationship between control of intra-ocular pressure and visual field deterioration. Am J Ophthalmol. 2000;130:429-440.
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