Magnetic Resonance Imaging Study on Blebs Morphology of Ahmed Valves
Joana Ferreira, Fernando Fernandes, Madalena Patricio, Ana Brás, Cristina Rios, Ingeborg Stalmans, Luís Abegão Pinto
Keywords :
Glaucoma, Intraocular pressure, Bleb morphology, Ahmed valve, Magnetic resonance imaging
Citation Information :
Ferreira J, Fernandes F, Patricio M, Brás A, Rios C, Stalmans I, Pinto LA. Magnetic Resonance Imaging Study on Blebs Morphology of Ahmed Valves. J Curr Glaucoma Pract 2015; 9 (1):1-5.
Purpose: To determine the morphometric parameters of filtration blebs of a valved aqueous humor drainage device.
Materials and methods: Orbital magnetic resonances imaging (MRI) was taken after implantation of an Ahmed valve (FP7 model). Outcomes of the analysis were intraocular pressure (IOP) and the bleb's morphometric analysis (volume, height, major and minor axis). Associations between IOP and the imaging-related study variables were explored by Spearman's correlation test.
Results: Eleven patients underwent orbital MRI examination. Recordings were taken after a mean of 2.7 months (1-6 months) after surgery. IOP was significantly lower than its preoperative values (17.6 ± 6.4 mm Hg vs 36.1 ± 6.4 mm Hg, p < 0.01). Mean bleb volume was 856.9 ± 261 mm3 and its height, major and minor axis were 5.77 ± 1.9, 14.8 ± 2.9 and 8.14 ± 3.6 mm, respectively. A positive correlation was detected between IOP and mean height (r = 0.77, p = 0.048) and major axis (r = 0.83, p = 0.03). Interestingly, the overall bleb volume was related to IOP levels immediately prior to surgery (r = 0.75, p < 0.01). Additionally, the posterior part of the plate was found to be displaced from the scleral surface in five cases (45%).
Conclusion: Ahmed valve's bleb morphology seems to correlate with both the pre- and postoperative IOP, which might suggest a clinical benefit of administering aqueous suppressants pre- as well as postoperatively. The plate of the device may show a significant dislocation from its initial surgical implantation site.
Minckler DS, Francis BA, Hodapp EA, Jampel HD, Lin SC, Samples JR, Smith SD, Singh K. Aqueous shunts in glaucoma: a report by the American Academy of Ophthalmology. Ophthalmology 2008 Jun;115(6):1089-1098.
Minckler DS, Vedula SS, Li TJ, Mathew MC, Ayyala RS, Francis BA. Aqueous shunts for glaucoma. Cochrane Database Syst Rev 2006 Apr;19(2):CD004918.
Desai MA, Gedde SJ, Feuer WJ, Shi W, Chen PP, Parrish RK 2nd. Practice preferences for glaucoma surgery: a survey of the American Glaucoma Society in 2008. Ophthalmic Surg Lasers Imaging 2011 May-Jun;42(3):202-208.
Minckler DS, Shammas A, Wilcox M, Ogden TE. Experimental studies of aqueous filtration using the Molteno implant. Trans Am Ophthalmol Soc 1987;85:368-392.
Wilcox MJ, Minckler DS, Ogden TE. Pathophysiology of artificial aqueous drainage in primate eyes with Molteno implants. J Glaucoma 1994;3(2):140-151.
Molteno AC, Fucik M, Dempster AG, Bevin TH. Otago glaucoma surgery outcome study: factors controlling capsule fibrosis around Molteno implants with histopathological correlation. Ophthalmology 2003 Nov;110(11):2198-2206.
Loeffler KU, Jay JL. Tissue response to aqueous drainage in a functioning Molteno implant. Br J Ophthalmol 1988 Jan;72(1):29-35.
Classen L, Kivela T, Tarkkanen A. Histopathologic and immunohistochemical analysis of the filtration bleb after unsuccessful glaucoma seton implantation. Am J Ophthalmol 1996 Aug;122(2):205-212.
Clarke CK, Minassian D, Khaw PT. The more flow surgery study: the effect of intraoperative 5FU on IOP control and trabeculectomy bleb appearance using the moorfields bleb grading system. IOVS 2005;46:E-Abstract 1221.
Wong TT, Mead AL, Khaw PT. Prolonged antiscarring effects of ilomastat and MMC after experimental glaucoma filtration surgery. Invest Ophthalmol Vis Sci 2005 Jun;46(6):2018-2022.
Detorakis ET, Engstrom RE, Straatsma BR, Demer JL. Functional anatomy of the anophthalmic socket: insights from magnetic resonance imaging. Invest Ophthalmol Vis Sci 2003 Oct;44(10):4307-4313.
Detorakis ET, Maris T, Papadaki E, Tsilimbaris MK, Karantanas AH, Pallikaris IG. Evaluation of the position and function of aqueous drainage implants with magnetic resonance imaging. J Glaucoma 2009 Aug;18(6):453-459.
Pirouzian A, Scher C, O'Halloran H, Jockin Y. Ahmed glaucoma valve implants in the pediatric population: the use of magnetic resonance imaging findings for surgical approach to reoperation. J AAPOS 2006 Aug;10(4):340-344.
Molteno AC, Suter AJ, Fenwick M, Bevin TH, Dempster AG. Otago glaucoma surgery outcome study: cytology and immunohistochemical staining of bleb capsules around Molteno implants. Invest Ophthalmol Vis Sci 2006 May;47(5): 1975-1981.
Molteno AC, Thompson AM, Bevin TH, Dempster AG. Otago glaucoma surgery outcome study: tissue matrix breakdown by apoptotic cells in capsules surrounding molteno implants. Invest Ophthalmol Vis Sci 2009 Mar;50(3):1187-1197.
Kadri OA, Wilcox MJ. Surface tension controls capsule thickness and collagen orientation in glaucoma shunt devices. Biomed Sci Instrum 2001;37:257-262.
Wilcox M, Kadri OA. Force and geometry determine structure and function of glaucoma filtration capsules. Ophthalmologica 2007;221(4):238-243.
Tsai JC, Johnson CC, Dietrich MS. The Ahmed shunt versus the Baerveldt shunt for refractory glaucoma: a single-surgeon comparison of outcome. Ophthalmology 2003 Sep;110(9): 1814-1821.
Lai JS, Poon AS, Chua JK, Tham CC, Leung AT, Lam DS. Efficacy and safety of the Ahmed glaucoma valve implant in Chinese eyes with complicated glaucoma. Br J Ophthalmol 2000 Jul;84(7):718-721.
Eibschitz-Tsimhoni M, Schertzer RM, Musch DC, Moroi SE. Incidence and management of encapsulated cysts following Ahmed glaucoma valve insertion. J Glaucoma 2005 Aug;14(4):276-279.
Pakravan M, Rad SS, Yazdani S, Ghahari E, Yaseri M. Effect of early treatment with aqueous suppressants on Ahmed glaucoma valve implantation outcomes. Ophthalmology 2014 Sep;121(9):1693-1698.
