SILICONE TUBE SHUNT IN SUPRACHOROIDAL SPACE IN RECALCITRANC

Silicone tube shunt operations to drain the aqueous from the anterior chamber to the suprachoroidal space were performed in 12 different types of refractory glaucomas in which the intraocular pressure ranged from 25 mmHg to 80 mmHg (mean 45.75 mmHg) even after maximally tolerated medical treatment or after conventional glaucoma surgery. The post-silicone tube shunt intraocular pressure ranged from 7 mmHg to 34 mmHg (mean 15. 83 mmHg) after a follow-up period ranging 2 months in some cases to 24 months in others. The intraocular pressure was controlled in all cases postoperatively either with the operation alone or with medical treatment or after repeat operation. The complications were very few except in one case in which there was hyphema as well as vitreous hemorrhage prior to operation because of trauma for which pars plana vitrectomy followed by second silicone tube shunt operation were performed and at the end enucleation had to be done. 1. Kathmandu Medical College, Sinamangal, Kathmandu, Nepal. 2. Institute of Clinical Ophthalmology, Kiryu, Gunma, Japan. Address for correspondence : Dr. K. J. D. Karki Senior Consultant Dept. of Ophthalmology Kathmandu Medical College, Sinamangal, Kathmandu being left to go atrophic either with uncontrolled intraocular pressure or phthisical with heroic cyclodestructive procedures the patients should have a better choice of controlling their intraocular pressure either to improve or maintain the vision or least of all to get rid of those nasty symptoms. Zorab1 was the first to implant a seton in 1912.


INTRODUCTION
Recalcitrant glaucomas that is, glaucomas treated unsuccessfully either with maximally tolerated medical treatment or with conventional glaucoma surgeries have become a challenge to the ophthalmologic community for a long time.Before Molteno' deserves all the credit for arousing the interest in modern day ocular drainage implants.
Krupin et al 3 used valved implants to control the drainage of aqueous.Schocket et al 4 increased the surface area for the diffusion of aqueous by putting the anterior chamber tube shunt to an encircling band.Later Krupin et al used a long tube and a 180 0 scleral explant.Even after such a long history of trials and tribulations of aqueous shunt operations the search for a better, cheaper material and a shorter, easier and effective method still goes on.Herein, we describe our experience with silicone tube shunt in suprachoproidal space in a prospective study carried out in the Institute of clinical opthalmology, Kiryu, Gunma, Japan.I).

The
The overall success with this operation alone was 66.66% and the remaining cases had intraocular pressure controlled with medical treatment or repeat shunt tube operation, the criteria for success rate as laid down in our objective being intraocular pressure 21 mmHg with or without medical and repeat surgical treatment with the improvement or retention of vision.
trabeculectomy is fashioned at the limbus and turned towards the cornea.Two ab externo incisions are made, one along the surgical limbus

DISCUSSION
Ocular drainage implants known in ophthalmic terminology as setons were tried to facilitate drainage of the aqueous humour from the anterior chamber into the subconjunctival and orbital spaces.The first perilimbal shunt coined 'Aqueoplasty' by Zorab was a silk thread drawn through a wound to create a tract or fistula between the anterior chamber and the subconjunctival space perilimbally.As this opened a door for the pioneers in this field, they tried to improve the materials as well as methods to shunt the aqueous away from the anterior chamber to a suitable site so that the intraocular pressure of a recalcitrant glaucoma could be lowered without any serious complication.The material has gone through a series of tests and trials so that a material which does not cause fibrosis around the distal end and block the aqueous from the anterior chamber could be found.7] To prevent fibrosis biologically inert materials were searched upon and translimbal shunts were designed. 2,3,16The problem of limited surface area for the diffusion of aqueous around the distal end of the shunt, was still there.However, this problem could be avoided by placing the distal end of the shunt tube either on a plate or an encircling band to create a reservoir and then placing it over the equatorial region of the sclera. 4,5,15,191][22] The highest 5 year life-table surgical success rate achieved after one plate in the updated study was in patients with aphakic/pseudophakic glaucoma (46%), followed by those with glaucoma in childhood (26%), glaucoma's with failed filters (25%) and patients with neovascular glaucoma 25%.The placement of a second plate increased the success rate 21 to 53%, 71%, 40% and 56% in patients with aphakic/pseudophakic glaucomas, those with failed filters, those with neovascular glaucoma's and those with glaucomas who were less than 13 years of age respectively.
To increase the surface area for diffusion of aqueous fluid, anterior chamber tube shunt to an encircling band (ACTSEB) procedure was first described in 1982.The reported success rates have varied with intraocular pressure control in 71% of eyes in unresponsive patients with an ACTSEB device. 23itially, Krupin-Denner device had a short perilimbal seton of a supramid tube sealed to a silicone rubber tube with a slit like valve.They modified it and added a long tube to the valve and drained the aqueous equatorially.Krupin et al reported intraocular pressure control in 68% of eyes with neovascular glaucoma.These different types of aqueous drainage implants have significant differences in their physical construction but they employ the same basic principle of draining aqueous from the anterior chamber to tho equatorial region translimbally.The Molteno implant procedure is the easiest to perform but the Schochet system is the least expensive.However the Molteno implant produced a statistically lower IOP at 6 months compared with the Schochet shunt. 24Hasan at el compared the effectiveness of glaucoma control between two drainage implants, the Baerveldt Model 350 and the Ahmed glaucoma valve (AGV), in patients with refractory glaucoma.They concluded that there is no significant advantage in glaucoma control over a 1-year period following surgery. 25e complications were similar in variety and nature in all these aqueous shunt operations.They included hyphema, hypotony, flat anterior chamber, corneal decompensation, Cataract., uveitis, Tenon's cyst, blocked tube, erosion of the tube and plate, choroidal detachment, retinal detachment and phthisis bulbi.
The material in the study is a simple silicone tube easily available everywhere.The operation is easy and takes a very short time to perform as this procedure does not need dissection to reach the equatorial region.The supra-choroidal space is a very large potential space for the diffusion of the aqueous and it should not be created by dissection.Moreover, the fibrous capsule formation and thereby blockage of the distal end of the shunt tubes as noticed in other procedures are not present in this procedure.The operation is performed in one stage and it can be repeated at the other quadrant of the limbus if the first operation does not control IOP.The complications like hypotony, hyphema, corneal decompensation, iritis, cataract and choroidal detachment were not noticed.The encouragement to explore this potential space to shunt the aqueous from the anterior chamber comes from the trabeculocyclostomy or trabeculostomy procedure by which the IOP is controlled and the choroidal detachment which is the most dreaded complication was never noticed. 25The chances of shunt tube erosion and late infection are absent as the tubes are put in a closed space.The parameters of success and failures of such types of operations are as varied as the diagnosis.age, sex and condition in which the operation is performed.

CONCLUSION
Looking at the complexities of recalcitrant glaucomas in which the silicone tube shunt operations were performed, being the easiest, cheapest and shortest operation without any serious complication that was expected therefrom and comparing the success rates of percentage from other shunt operations the silicon tube shunt operation in suprachoroidal space needs serious consideration, thought and future study.
nature of the operation was discussed with the patient and informed consent obtained.The study included 12 different cases of recalitrant glaucomas with uncontrolled intraocular pressure either with maximum tolerated single drug or multiple drugs medical treatment or after single or multiple conventional glaucoma surgeries or combined medical and surgical treatment.The operation is done under peribulbar anesthesia.A 6-7 mm limbus based conjunctival flap with or without Tenon's capsule is dissected at either the upper nasal or upper temporal quadrant of the limbus.A quadrangular 4 x 4 mm half thickness scleral flap as in

Fig. 4 :
Fig. 4 : One End of Silicone Tube Inserted in Anterior Chamber and the other end inserted in Suprachoroidal Space

Fig. 5 :
Fig. 5 : The Tube Sutured to the Scleral Bed