The efficacy of Ahmed glaucoma valve drainage ...

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forceps which we find greatly facilitates insertion of the Ahmed glaucoma valve (AGV) tube in to the AC. The tube inserter. Figure 1: Tube insertion forceps.

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The efficacy of Ahmed glaucoma valve drainage devices in cases of adult refractive glaucoma in Indian eyes Dear Editor We read with interest the article by Parihar et al. [1] We congratulate the authors for their study and wish to make a few observations. While the authors have mentioned that tube insertion into the anterior chamber (AC) is done through a paracentesis track made with a 22-G needle and also that the use of viscoelastic through this needle track assists tube insertion there is no mention of the use of a special tube inserter forceps which we find greatly facilitates insertion of the Ahmed glaucoma valve (AGV) tube in to the AC. The tube inserter

(New World Meditec Inc, CA) is a stainless steel forceps with a serrated grip and notched tip [Fig. 1] which provides rigidity to the AGV tube for easy insertion into the anterior or posterior chamber unlike any other serrated or tying forceps which may kink or damage the tube. In situations where there is extensive conjunctival scarring and in revision surgeries the use of preserved scleral allograft obtained from an eye bank is suitable for covering the tube. It is biocompatible and can be trimmed to any size or shape. Ethanol-preserved sclera should be soaked in balanced salt solution for about 20 min before use. The use of such allografts has not been discussed by the authors. The authors have enlisted many complications noted in their study following the use of the AGV in refractive glaucoma. Tube retraction is another complication which has been encountered by us in some cases. Tube retraction [Fig. 2a] refers to the retraction of the tube from the AC either into the scleral tunnel which had been fashioned for tube placement or into the subconjunctival space. This results in failure of aqueous drainage and resultant elevation in IOP. When this occurs and the tube is too short to be re-inserted the options for management include replacement with another AGV,

Figure 2a: Tube retraction following AGV Figure 1: Tube insertion forceps

Figure 2b: Tube extender

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Figure 2c: Tube extender inserted into the AC and sutured

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Indian Journal of Ophthalmology

reinsertion of the tube into pars plana (a pars plana clip may be used) or a tube extender[2] can be used to lengthen the tube. The tube extender (New World Meditec Inc, CA) is made of medical grade silicone with a length of about 24 mm and outer diameter of 0.635 mm. The proximal end can be attached to the existing AGV tube after removing it from the AC while the distal end can be inserted into the AC through a new paracentesis opening made with a 22-G needle. The tube extender is then sutured to the underlying sclera. We have used a tube extender in such situations [Figs. 2b and 2c] with good results.

Vol. 58 No. 3

The tube extender is well reported in the literature[2] and has been used in situations as quoted by the authors. We have not had an occasion to use the extender as yet as none of our

Ariga Murali Swamy Eye Clinic, 11 South Mada Street, Villivakkam, Chennai-600 049, India Correspondence to: Dr. Ariga Murali, Swamy Eye Clinic, 11 South Mada Street, Villivakkam, Chennai 600049, India. E-mail: [email protected]

References 1. Parihar JK, Vats DP, Maggon R, Mathur V, Singh A, Mishra SK. The efficacy of Ahmed glaucoma valve drainage devices in cases of adult refractive glaucoma in Indian eyes. Indian J Ophthalmol 2009;57:345-50.

Figure 1: Modified AGV tube insertion forceps

2. Sarkisian SR, Netland PA. Tube extender for revision of glaucoma drainage implants. J Glaucoma 2007;16:637-9. DOI: 10.4103/0301-4738.62667 

PMID: ***

Authors' reply Dear Editor, We thank and highly appreciate Murali for his interest in our article[1] and their insightful and well-articulated comments. Their observation regarding the insertion forceps is absolutely correct. In fact insertion forceps facilitate insertion of tube through 22/23 gauze needle track with precision and ease. Although we have not commented on it specifically, the insertion forceps have been used in all cases. In fact one of the photograph [Fig.6] in the original article, shows this instrument in use.[2] In our practice we found the insertion forceps designed by Dr Ahmed to be a little cumbersome while in use under moderate to high magnification of operating microscope. The author feels that these forceps are more heavy and large in size as compared to other microsurgical instruments being used in this surgery. Considering this observation, we have modified the insertion forceps which is manufactured by OVATION International, Jaipur (Rajasthan) India [Fig. 1]. This modified tube insertor forceps is made up of titanium, weighing 8g as compared to 22 g of the original forceps. The groove of the forceps is further modified to hold and insert the tube much more conveniently. Over and above, the forceps are much smaller in size, having a length of 110 mm as compared to 120 mm, while also retaining all the privileges of the original insertion forceps designed by Dr Ahmed [Figs. 2 and 3].

Figure 2: Modified AGV tube insertion forceps compared with Dr Ahmed's original forceps

Figure 3: Insertion of AGV tube with the help of modified tube insertion forceps

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