Are There Problems with Non-penetrating Glaucoma Surgery?
Figure 1: Qualitative Comparison of Tonometric Success Rates Between Trabeculectomy and NPGS
controlled glaucoma in a patient undergoing cataract surgery who wishes to avoid medication; and
patient unhappy on topical hypotensives. n Hypotony Target IOP Trabeculectomy + MMC
DC = deep sclerectomy; IOP = intraocular pressure; MMC = mitomycin C; NPGS = non-penetrating glaucoma surgery; VC = viscocanalostomy.
What Does the Lead Author Do?
With limited although similar experience in both VC/PhacoVC and trabeculectomy surgery, the lead author’s preferred surgical techniques are indicated as follows.
Trabeculectomy and MMC for: • • • •
uncontrolled open-angle glaucoma with severe damage;
open-angle glaucoma with damage occurring at modest IOP levels; neovascular glaucoma that is quiescent;
severe chronic angle-closure glaucoma with separate-site phacoemulsification; and • abnormal-angle anatomy.
PhacoVC/VC for: •
uncontrolled open-angle glaucoma with moderate damage;
• uveitic glaucoma (to reduce post-operative hypotony and inflammation);
chronic angle-closure glaucoma with moderate damage; patient who would otherwise undergo phacotrabeculectomy;
• only eye; • split fixation; • uncontrolled ocular hypertension;
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9. Carassa R, Bettin P, Fiori M, Brancato R, Viscocanalostomy Conclusions in 2012
As the level of evidence is mainly moderate to weak, it would be dangerous to conclude too much. Regarding DS, the addition of an implant improves the longevity of success rates; the concomitant use of MMC may further improve success rates, but with the risk of late bleb leaks; concomitant phacoemulsification may also improve success rates. With VC, tight suturing of the scleral flap may be beneficial to success rates, along with same-site phacoemulsification.Th
e best mid-term success rates were obtained by Wishart and Dagres28
PhacoVC (three-year success rate of 89 %). The best long-term results were obtained from Bissig et al.16
with DSI (10-year success rate of 48 %).
VCc offers an alternative to VC and DS, but with it comes a significant equipment cost. Attention to surgical technique appears crucial to determine whether or not the procedure works ‘in your hands’ and when comparing results between studies. n
versus trabeculectomy in white adults affected by open-angle glaucoma. A 2-year randomized controlled trial, Ophthalmology, 2003;110:882–7.
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13. Stegmann R, Pienaar A, Miller D, Viscocanalostomy for open- angle glaucoma in black African patients, J Cataract Refract Surg, 1999;25:316–22.
14. Khairy HA, Green FD, Nassar MK, Azuaro-Blanco A, Control of intraocular pressure after deep sclerectomy, Eye, 2009;20:336–40.
15. Chiselita D, Non-penetrating deep sclerectomy versus trabeculectomy in primary open-angle glaucoma surgery, Eye, 2001;15:197–201.
16. Bissig A, Rivier D, Zaninetti M, et al., Ten years follow-up after deep sclerectomy with collagen implant, J Glaucoma, 2008;17:680–6.
17. Kozobolis V, Christodoulakis E, Tzanakis N, Zacharopoulos I, et al., Primary deep sclerectomy versus primary deep sclerectomy with the use of mitomycin C in primary open-angle glaucoma, J Glaucoma, 2002;11:287–93.
18. Guedes R, Guedes V, Chaoubah A, Does phacoemulsification affect the long-term success of non-penetrating deep sclerectomy? Ophthalmic Surg Las Imaging, 2010;41:228–35.
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22. Ang G, Varga Z, Sharaawy T, Postoperative infection in penetrating versus non-penetrating glaucoma surgery, Br J Ophthalmol, 2010;94:1571–6.
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24. Johnson D, Johnson M, How does nonpenetrating glaucoma surgery work? Aqueous outflow resistance and glaucoma
When very low IOP is the target, augmented trabeculectomy surgery offers the best chance of success. The question is not whether trabeculectomy can achieve lower IOPs; the question is, lower IOP at what cost in terms of risk of complications? By offering surgery earlier in the course of the disease (when possible) when the target IOP might be higher, it is possible to choose a safer alternative to trabeculectomy. If the target IOP is higher, then the success rate of any surgery is higher. Figure 1 summarizes these points. By adopting this paradigm, more patients would undergo glaucoma surgery earlier in their disease process. Whereas, a lot of the time, trabeculectomy is a necessity, VC or DS may be an option.
PhacoVC/VC could be offered earlier in the course of the disease, even when glaucoma is not progressive; if a stable glaucoma patient requires cataract extraction, the patient could be offered PhacoVC in an attempt to discontinue topical hypotensives. If the patient does not like using topical hypotensives, PhacoVC/VC can be considered.
While a low target IOP and/or inability to consider ongoing hypotensives argues for augmented trabeculectomy, post-operative complications that might be visually dangerous support VC and DS as options.
US OPHTHALMIC REVIEW
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