Supra-Tenon Capsule Placement of Baerveldt Implant

Department of Ophthalmology, California Pacific Medical Center, San Francisco, CA

Aileen Sy, MD and H. George Tanaka, MD

Methods• Retrospective chart review was performed on all patients

receiving Baerveldt implants from March 2012 to March 2014. All supra-Tenon GDD were 250 mm2 implants and all infra-Tenon GDD were 350 mm2.

• Information gathered included age, gender, race, type of glaucoma, pre-surgical visual acuity (VA), intraocular pressure (IOP) and number of glaucoma drops, post-surgical visual acuity, intraocular pressure and number of glaucoma drops, follow-up time and complications.

• Baseline demographics were analyzed by implant location with Fisher’s exact test for categorical variables and Wilcoxon rank-sum test for continuous variables. T-test and multilinear regression models were used to analyze outcome measures.

Purpose• To compare the efficacy of supra-Tenon placement of 250

mm2 versus infra-Tenon placement of 350 mm2 Baerveldt glaucoma drainage device (GDD).

Background• Placement of GDDs has traditionally been beneath the

Tenon capsule.

• Tenon capsule has been found to be pro-inflammatory and is thought to contribute to GDD bleb fibrosis and failure.1,2

• Supra-Tenon placement of GDD has been proposed as a means of eliminating fibrosis from Tenon tissue.1,2,3,4

• Supra-Tenon capsule placement of the Molteno (130 mm2) and Molteno 3 (175 mm2) glaucoma implant has been reported in patients failing prior filtration or implant surgery. Results showed effective intraocular pressure control and bleb formation, supporting supra-Tenon placement as a viable surgical option.3,4 Additionally, supra-Tenon placement appeared to offset any benefit from larger plate size.

• No prior studies have investigated supra-Tenon placement of the more commonly used Baerveldt implant in eyes without prior GDD implant.

Conclusions and Future Investigations

References1. Freedman J. Molteno Developments in Traditional Outflow Implants. In: Samples

JR, Ahmed IIK, eds. Surgical Innovations in Glaucoma. New York: Springer Science+Business Media; 2014:209-220.

2. Freedman J, Iserovich P. Pro-inflammatory cytokines in glaucomatous aqueous and encysted Molteno implant blebs and their relationship to pressure. Investigative Ophthalmology & Visual Science. Jul 2013;54(7):4851-4855.

3. Freedman J, Bhandari R. Supra-tenon capsule placement of original Molteno vs Molteno 3 tube implants in black patients with refractory glaucoma: a single-surgeon experience. Archives of Ophthalmology. Aug 2011;129(8):993-997.

4. Freedman J, Chamnongvongse P. Supra-Tenon's capsule placement of a single-plate Molteno implant. The British Journal of Ophthalmology. May 2008;92(5):669-672.

Table 1. Baseline Characteristics

AcknowledgmentsThanks to Pacific Vision Foundation for their support of this research.

Results• No significant difference in age, gender ratio, pre-operative

IOP, pre-operative number of IOP lowering medications, prior surgeries or pre-operative VA was found.

• A shorter follow up in supra-Tenon implant group was noted, but not found to be statistically significant (p=0.40).

• No difference in post-operative IOP was found (p=0.86).

• Fewer IOP lowering medications were required in the supra-Tenon implant group at last follow-up (p=0.09), significant by p<0.1 criteria but not by p<0.05 criteria.

• No difference in post-operative VA was found (p=0.25).

• Time to pulling tube-occluding stent was shorter in the infra-Tenon group, but not statistically significant (p=0.14).

• The most common post-operative complication was hypotony and choroidals (4/26 supra-Tenon, 5/32, infra-Tenon). Other complications in the supra-Tenon group included an encysted bleb restricting extraocular movements and focal tube exposure, one case of each. Infra-Tenon complications included binocular diplopia, flat AC, hyphema, high IOP and exposed plate, one case of each.

• Surgical revisions were required in three (11.2%) supra-Tenon cases and three (9.4%) infra-Tenon cases.

Figure 1. Supra-Tenon Surgical Technique

Table 2. Post-surgical Outcomes

• Supra-Tenon placement of the smaller 250 mm2 Baerveldt implant can effectively control IOP as compared to the larger 250 mm2 infra-Tenon implant placement. It appears supra-Tenon placement negates smaller implant size.

• Rate of complications did not appear to be higher with supra-Tenon placement.

• Supra-Tenon placement of Baerveldt implant may allow for fewer IOP lowering medications than traditional infra-Tenon placement.

• Success of supra-Tenon placement of Baerveldt implant in patients with prior infra-Tenon Ahmed implant is currently being evaluated.

Supra-Tenon (N=26)

Mean (median)

Infra-Tenons (N=32)

Mean (median)

P-value

Age 70 (72) 69.3 (72) 0.94

Gender (M:F) 1:1 1:1 1.00

Prior surgeries (No.)

1.2 (1) 1.3 (1) 0.70

Length of follow-up (months)

9.6 (9) 12.7 (10.5) 0.40

Pre-operative IOP

24.2 (22) 26.0 (23) 0.70

Pre-operative medications (No.)

3.6 (4) 3.4 (4) 0.39

Pre-operative visual acuity (VA, logMAR)

0.71 (0.3) 0.70 (0.3) 0.98

Supra-Tenon (N=26)

Mean (median)

Infra-Tenons (N=32)

Mean (median)

P-value

Post-operative IOP

12.6 (13) 12.3 (12) 0.86

Post-operative medications (No.)

1.08 (0) 1.84 (2) 0.09

Post-operative VA (logMAR)

0.67 (0.3) 0.95 (0.4) 0.25

Time to pulling tube-occluding stent (days)

47.6 (32) 33.4 (28) 0.14

Surgical revision 3 (11.2%) 3 (9.4%)

Second glaucoma procedure

0 1 (3.1%)