1. DW.Lee, NC Cho, MJ Kim, EY Kwen
The early hypotony protection effect of intraoperative injection of viscoelastc material in trabeculectomy
DW.Lee, NC Cho, MJ Kim, EY Kwen
Department of Ophthalmology, Chonbuk National University Medical School, Korea

2. Purpose
Despite fewer complication of alternative procedure for glaucoma like deep sclerectomy & argon laser suture lysis, viscocanalostomy,
trabeculectomy has been gold standard surgical procedure for glaucoma because of it’s broad indication & supporting effectiveness.
The viscoelastic substance whould help maintain the anterior chamber, prevent hypotony, reduce hyphema and delay filtering bleb scarring after trabeculectomy.
But, there also has been some reports showing not much difference when not using viscoelastics.
We evaluated the effects of viscoelastic substance on prevention of early postoperative hypotony after trabeculectomy.

3. Method
We prospectively evaluated  40 eyes of 38 patients who underwent trabeculectomy by 1 surgeon from January 2005 to August 2007.
They  were randomized into two groups.(group A and B).
Standard trabeculectomy with 0.3% Mitomycin C was done under retrobulbar anesthesia.

4. Method
In group A of 23 eyes was used about 0.1ml of Viscoat®(Alcon, U.S.A.) to reform the anterior chamber after conjunctival suture.
In the other group B of 17 eyes was used only balanced salt solution(BSS) for anterior chamber reformation at the completion of the procedure.
We compared intraocular pressure & early complications for postoperative 1 week between the 2 groups.
Student’s t-test was used for visual acuity and IOP, chisquared test was used for the evaluation of the complications.

5. Results
The mean age of the patients was 51.8±18.9, 58.1±11.4 in group A and B. The causing diseases were open angle glaucoma 34%, 19%, angle closure glaucoma 21%, 24%, neovascular glaucoma 17%, 29%, and others 26%, 29% respectively in group A and B.
The mean intraocular pressure(mmHg) was 35.9, 38.1 (p>0.01) preoperatively, 14.7, 10.7 (p>0.01) at postoperative 1 day, and 12.4, 11.3 (p>0.01) at posterative 1 week, respectively in group A and B.
Postoperative shallow anterior chamber in 1 eye of group A and 2 eyes of group B, hyphema in 1 eye of group A and 2 eyes of group B and choroidal detachment in 2 eyes of group B. There were no statistical different incidences between the two groups(p>0.01).
Postoperative IOP rise over 30mmHg developed in 2 eyes of group A. There were no statistical different incidences between the two groups(p>0.01).

6. Results Characteristics Group A Group B 23 17 51.8 58.1 35.9 38.1
Eyes 23 17
Mean age
51.8
58.1
Preoperative intraocular
pressure
35.9
38.1
Type of Glaucoma
Primary open angle 8 3
Chronic angle closure 5 4
Neovascular glaucoma
Pseudoexfoliative 1
Uveitis 2
Angle recession & trauma

7. Results Mean intraocular pressure (mmHg)
Group 1
Group 2
P-value
Preoperative
35.9
38.1
P>0.01
Postoperative 1day
14.7
10.7
P<0.01
Postoperative 2day
12.3
10.9
Postoperative 7day
12.4
11.3

8. Results Complications Group 1 Group 2 P-value
Hypotony or shallow anterior chamber
1(4%)
2(12%)
P>0.01
Choroidal detachment
1(6%)
Early intraocular pressure peak
2(8%)
hyphema

9. Conclusion
Viscoat®(Alcon, U.S.A.) was composed of 3% sodium hyaluronate & 4% sodium chondroitin sulfate.
Sodium chodroitin sulfate is viscoelastic biopolymer & removed from anterior chamber after 24~30 hours, unlike sodium hyaluronate that was metabolized.
Viscoat injection after trabeculectomy has been believed that has protective effect for early hypotony since Blondeau reported, fewer early hypotony and anterior chamber shallowing after using viscoat, which were responsible for better visual acuity.
And it also reported that viscoat injection did not ensure more favorable outcomes or decreased incidence of complications.

10. Conclusion
In our survey, injecting some viscoelastic substance into the anterior chamber may help prevent postoperative hypotony & complication to some degree, but statistically significant difference was not demonstrated by between two–group comparison.
This might be substituted by other safer procedures such as more tighter closure of scleral flap with argon laser suture lysis or releasable sutures.