br Discussion Glaucoma drainage implants

Discussion
Glaucoma drainage implants have been used successfully for the treatment of complicated glaucomas including NVG; aphakic and pseudophakic glaucoma; glaucomas with multiple filtering procedures; post penetrating keratoplasty glaucoma; pediatric glaucoma; and uveitic glaucoma. One of the common early postoperative complications is overdrainage resulting in shallow AC, hypotony, and choroidal detachment. There are various types of glaucoma drainage implants available in the market. Some of them have a set resistance mechanism to minimize over-drainage in the early postoperative period. Those without set resistance mechanism may require either a two staged procedure or ligature technique. The AGV implant employs a built in Venturi valve to provide resistance to aqueous flow.
In our study, the AGV implant was able to decrease the mean (SD) preoperative IOP from 37.0±12.1mmHg to 18.4±10.7mmHg at 3months and 18.0±14.1mmHg at 1year postoperatively. The success rate achieved was 79%. Most case series reported success rates between 67% and 94%, depending on their criteria for success.
The overall success rate in this study compares favorably with the success rates of other glaucoma drainage devices. The Baerveldt implant had a success rate of 72%, and the Molteno implant showed 58–95% success rate, all of the these glaucoma drainage implants divert aqueous from the eye to the tenon space posterior to the limbus, which may explain similar success rates with different implants.
Hypotony and complications of hypotony are common during the immediate postoperative purchase NCT-501 after nonvalved glaucoma drainage implants. The most common complications after the Baerveldt implant were hypotony (32% of eyes), in the current study, we found complications associated with hypotony in the immediate postoperative period less frequently (18%). No eyes in our study required surgical anterior chamber reformation.
Neovascular glaucoma was the most common preoperative diagnosis (42.4%) in our series and it also carries the highest failure rate in our study (54.5%). No other types of glaucoma were found to have associated with such a high failure rate in our series. It has been well shown that NVG is associated with a much higher risk of failure than other types of glaucoma.
The hypertensive phase reported to be as high as 20–40% incidence in other implant series was not distinct in our series. Although the mean IOP at 3months was slightly higher than that in 1year, it might have been modified by the medications.
Tube obstruction occurred in 6 cases (18%) it was due to blood in 3 cases, iris or cornea in 2 cases and the last case had presumed obstruction manifested by increases in intraocular pressure during the first postoperative week, with an apparently patent tube on slit lamp examination. The IOP returned to normal spontaneously or with digital pressure in all the cases. We did not observe any instances of tube occlusion by the posterior capsule or irreversible valve membrane adhesion which may be described in eyes with AGV implants.

Conclusion

Introduction
Glaucoma is a multifactorial optic neuropathy known to cause progressive loss of retinal ganglion cells and their axons. Evaluation of the retinal nerve fiber layer (RNFL) and optic nerve head (ONH) is a crucial step in diagnosing and monitoring glaucoma. It has been suggested that early detection and treatment of glaucomatous optic neuropathy may reduce the incidence of blindness from glaucoma.
Staging glaucomatous damage into broad categories of damage such as, mild, moderate, and advanced enhances management. It promotes careful assessment and documentation of clinical damage, thereby facilitating monitoring for stability versus progression and provides a common language for both clinical and research purposes.
Automated computerized devices can discriminate between normal and glaucomatous eyes, objectively with good results. These include scanning laser ophthalmoscopy, scanning laser polarimetry and optical coherence tomography (OCT). Each can analyze and quantify the optic nerve and RNFL thickness allowing broad staging of structural damage. However these expensive and sophisticated technologies are evolving faster than clinical assessment of their utility.