Clinical Evaluation Of The Ahmed Glaucoma Valve Implantation For Treatment Of Refractory Glaucoma

Refractory glaucoma refers to the glaucoma that the intraocular pressure is difficult to control in the normal range even the conventional filtration surgery or with adjunctive antimetabolites, as well as auxiliary and maximum tolerance of anti-glaucoma drugs are used. It includes the neovascular glaucoma(NVG) caused by various reasons; secondary glauco- ma caused by aphakic or pseudophakic, uveitis, keratoplasty, pars plana vitrectomy, etc.; primary glaucoma and pediatric glaucoma after several failed filtration surgery; traumatic glaucoma and iridocorneal endothelial syndrome, and so on.Modern ophthalmic microsurgery technology makes the success rate of most glaucoma filtration surgery achieve 70% to 90%, but for refractory glaucoma, as difficult to establish an effective filtering channel owing to the fibrotic effect around bleb, the success rate is only 11% -52%. At present, the treatment of refractory glaucoma consists of trabeculectomy with adjunctive antimetabolites, cyclodestruction surgery (such as cryotherapy on ciliary,laser cyclophotocoagulation or ultrasound treatment) and glaucoma drainage device implantation. Trabeculectomy with adjunctive antimetabolites sometimes still has difficulty in forming a functional filtering bleb. Cyclodestruction surgery is mainly applied to refractory glaucoma of absolute period or near absolute period.Because of the froward quantity of operation, the strong inflammatory effects after surgery, the serious complications, the patient suffer from a great pain, moreover, because of the potential possibility of hypotony and phthisis bubli resulted from excessive destruction of the ciliary body, it should be carefully used on patients with good visual acuity or monocular visual acuity. The appearance of glaucoma drainage devices(GDDS) provides a new and effective alternative for the treatment of refractory glaucoma. Nearly a dozen years, because of a large disc, easily-inserted drainage tube, with a one-way pressure regulator valve, lower rate of early hypotony and correlative complications, the Ahmed glaucoma valve(AGV) are widely used in the clinical treatment of refractory glaucoma. This paper analysed the efficacy evaluation and complications of the 30 patients(31 eyes) with refractory glaucoma who underwent Ahmed glaucoma valve implantation operation in our hospital to guide future clinical treatment.A retrospective chart view of consecutive patients who underwent placement of an AGV with adjunctive mitomycin-C(MMC) in the ophthalmic department of the second hospital of Jilin University from October 2002 to November 2007 was performed. There were 30 patients (31 eyes), 16 males (16 eyes), 14 females (15 eyes). The mean age was 52.6 years(range: 18-75 years). There were 24 cases(24 eyes) of neovascular glaucoma (77.4%),3 cases(4 eyes)of aphakic1 case,2 eyes of failed filtration surgery, 1 eye of traumatic glaucoma who underwent pars plana vitrectomy one and a half months before. According to whether partially ligating the tube during the operation, we divided all patients into Group A (no ligation,16 eyes)and Group B(with ligation,15 eyes). According to whether using the allogenic sclera in the operation or not, we divided all patients into Group C (didn't use,20eyes)and Group D(used,11 eyes).The average preopertive intraocular pressure(IOP) was (48.6±10.1)mmHg (range: 27-60mmHg,1mmHg=0.133kPa). The mean preoperative medication species were 3.4±0.5. 12 eyes were absent of light perception, 10 eyes had light perception, 5 eyes could see fingers movement, 2 eyes could identify finger count, and 2 eye had visual acuity of 0.02-0.1. All patients were followed up for 6 to 16 months with an average of 11 months. Surgical evaluation criteria are as follows: success criteria: 6 mmHg≤IOP≤21 mmHg. There are researchers also including post-operative visual acuity decreased to no more than 2 lines (Snellen). Complete success: without medication; qualified success: with one or more medication; failure criteria: IOP>21mmHg or IOP < 6 mmHg, additional glaucoma surgery, removal or replacement of the GDDS, or devastating complications (including endophthalmitis, chronic hypotony, malignant glaucoma, retinal detachment, severe choroidal detachment), the loss of light perception or phthisis bulbi. All patients in this group didn't have significant vision change nor devastating complications, so the success rate is measured in terms of the control level of intraocular pressure.On the last visit, IOP of 18 eyes were controlled in the normal range,2 of which(all are NVG) were controlled well after excision of encapsulated belb 6 months postoperatively. IOP of 10 eyes can be controlled in the normal range with one or more medication. The total success rate of first operation was 83.9%. IOP of 3 eyes still couldn't be controlled in the normal range with medications, which were considered failure.The average IOP of Group B on the first day, first week, first month, third month, sixth month, last visit were (8.73±3.04) mmHg, (13.55±5.37) mmHg, (18.45±5.20) mmHg, (17.27±5.24) mmHg, (15.91±2.55) mmHg, (15.82±2.86) mmHg, respectively. Compared with the average preoperative IOP of Group B (48.18±11.18) mmHg (with paired t test), t = 14.04,13.05,9.11,10.24, 11.34,11.36 respectively, P <0.001, the difference was statistically significant. The average kinds of medication of Group B on the first day, first week, first month, third month, sixth month, last visit were 0,0,0.4±1.0,0.8±1.0,1.0±1.2,1.0±1.3 respectively. On the first week, first month, third month, sixth month,the complete success rate were 100%,80.0%,73.3%,66.7% respectively,the qualified success rate were0,13.3%,13.3%,20.0% respectively。The average IOP decreased significantly in the first week, and after a peak IOP at the first month, the average IOP decreased to 6 months postoperatively, then IOP stabilized. At the same time, the kinds of medication gradually increased from 1 month postoperatively. The success rate decreased slightly over time extended.There was no significant change in visual acuity of all patients. Of 24 eyes of NVG, neovascularization gradually disappeared in 2-4 weeks postoperatively in 19 eyes whose IOP were controlled well. The other 5 eyes also reduced to different degrees.Postoperative complications: In Group A, 5 eyes(31.3%) had early shallow anterior chamber, 3 of which with hypotony, and 1 occurred shallow anterior chamber ofⅢdegree. In Group B,3 eyes(20.0%) had early shallow anterior chamber, 1 of which with hypotony, and noⅢdegree shallow anterior chamber; 5 eyes of 4 cases in Group B occurred hypertensive phase from 1 month postoperatively;2 cases in Group C that didn't use allogeneic sclera in the operation, the drainage tube exposed after 3 months, while there wasn't in Group D; Encapsulated bleb occurred in 5 eyes, and IOP of 2 eyes were with good control after excision of encapsulated bleb at the sixth month.Conclusion:1. AGV implantation is a simple, less pain, less trauma, feasible and effective method on treating refractory glaucoma.2. Using allogeneic sclera to cover drainage tube in the AGV implantation operation can play a positive role in preventing exposure .3. Partially ligating the drainage tube using absorbable suture during the AGV implantation operation can play a positive role in preventing early postoperative hypotony and shallow anterior chamber.4. AGV implantation has a high rate of hypertensive phase and bleb encapsulation, which has a great impact on the success rate. This underscores the importance of close follow-up and timely processing of complications during early postoperative period after placement of an AGV.