Conjunctival Incisions for Glaucoma Drainage Device Implant
Conjunctival Incisions for Glaucoma Drainage Device Implant
Purpose: To determine the effect of conjunctival incision location on the long-term efficacy of nonvalved glaucoma drainage devices.
Materials and Methods: We conducted a retrospective review of patients ≥18 years of age with uncontrolled glaucoma [intraocular pressure (IOP) ≥18 mm Hg] who underwent glaucoma drainage device implantation. A comparison was made of a limbal-based (LB-BGI) versus fornix-based (FB-BGI) conjunctival flap during placement of a 350-mm Baerveldt glaucoma implant (AMO, Santa Ana, CA) in subjects with at least 1 year of follow-up data. The primary outcome measure was IOP; secondary outcome measures were medication burden, visual acuity, and surgical complications.
Results: One hundred sixty eyes of 147 glaucoma patients were included. Two years after surgery, the IOP in the LB-BGI group was 14.3±5.3 mm Hg and in the FB-BGI group 13.1±4.7 mm Hg (P =0.47). Overall success of IOP control was achieved at the final visit (range 1 to 5 y) in 90% of the LB-BGI group and 87% of the FB-BGI group (P =0.63). The medication burden of the 2 groups at 1 and 2 years after surgery was not statistically significantly different. Worsening of visual acuity by more than 2 lines was not statistically different between the groups 2 years after the surgery and at the final visit (P =0.47, P =0.60, respectively). A greater number of eyes developed endophthalmitis and were more likely to undergo subsequent tube revision in the FB-BGI group, but the differences were not significant.
Conclusions: Both incision techniques were equally effective in controlling IOP. Each surgical approach has its advantages and this study suggests that either technique may be used safely and effectively.
Since their introduction in the 1970s, glaucoma drainage devices (GDDs) have generally been reserved for refractory cases of glaucoma. However, in the past decade, they have been used in earlier stages of glaucoma and their use has nearly quadrupled over a 10-year period. GDDs divert aqueous humor to an area remote from the limbus to promote the development of a bleb in healthier conjunctiva. Long-term success for GDDs has ranged from 50% to 88% in aphakia and or pseudophakia and from 61% to 100% in eyes with failed trabeculectomy surgery, 75 to 100% for uveitic glaucoma, 44% to 100% for developmental glaucoma, and 22% to 78% for neovascular glaucoma. Studies to date have not differentiated between the 2 conjunctival surgical approaches used when implanting this device.
The conjunctival flap created during insertion of a GDD can be limbus-based (LB) or fornix-based (FB). Each flap technique has its advantages and disadvantages. The LB incision provides better visualization during placement of the implant's plate and also results in a smoother conjunctival surface at the limbus, promoting patient comfort postoperatively. An LB incision also avoids the destruction of limbal stem cells, which may be deficient in some patients undergoing GDD surgery (eg, aniridia, chemical injury). However, surgical exposure is limited during tube insertion into the anterior chamber and extensive conjunctival scarring may preclude this type of approach. This technique also places an incision in the conjunctival fornix in close proximity to where one might expect the bleb to form, potentially affecting capsule formation and resistance to flow. In contrast, an FB incision allows easier visualization at the limbus during tube insertion and places the incision site away from the area of bleb formation; however, posterior visualization is more difficult, making placement of the implant's plate challenging unless a wide peritomy or radial relaxing incision is created.
The FB conjunctival flap is the more popular incision technique. In the tube versus trabeculectomy (TVT) study, a multicenter, randomized clinical trial designed to prospectively compare the safety and efficacy of nonvalved tube shunt surgery versus trabeculectomy with mitomycin C, 82 of 107 (77%) patients randomized to the tube group had tubes placed via an FB conjunctival flap and 25 of 107 (23%) were placed via an LB conjunctival flap technique. A comparison of outcome measures between these 2 surgical techniques was not assessed by the TVT investigators.
Capsule formation around a GDD implant results from a foreign body reaction to the implant: macrophages and giant cells accumulate at the implant surface followed by fibroblast proliferation and collagen deposition with capillary formation. Stabilization of the implant to the scleral surface, varying the timing and intensity of aqueous flow to the capsule, size and shape of the implant, and the use of antifibrotic agents are all modifications that affect capsule fibrosis and subsequent IOP control. However, it is not known whether the proximity of the conjunctival incision affects capsule fibrosis and IOP control. We therefore conducted a retrospective study to compare the effects of LB versus FB conjunctival flaps on the efficacy of IOP control after GDD surgery. We hypothesized that the intraocular pressure (IOP) would be lower in the FB approach because the incision site is placed away from the site of bleb formation.
Abstract and Introduction
Abstract
Purpose: To determine the effect of conjunctival incision location on the long-term efficacy of nonvalved glaucoma drainage devices.
Materials and Methods: We conducted a retrospective review of patients ≥18 years of age with uncontrolled glaucoma [intraocular pressure (IOP) ≥18 mm Hg] who underwent glaucoma drainage device implantation. A comparison was made of a limbal-based (LB-BGI) versus fornix-based (FB-BGI) conjunctival flap during placement of a 350-mm Baerveldt glaucoma implant (AMO, Santa Ana, CA) in subjects with at least 1 year of follow-up data. The primary outcome measure was IOP; secondary outcome measures were medication burden, visual acuity, and surgical complications.
Results: One hundred sixty eyes of 147 glaucoma patients were included. Two years after surgery, the IOP in the LB-BGI group was 14.3±5.3 mm Hg and in the FB-BGI group 13.1±4.7 mm Hg (P =0.47). Overall success of IOP control was achieved at the final visit (range 1 to 5 y) in 90% of the LB-BGI group and 87% of the FB-BGI group (P =0.63). The medication burden of the 2 groups at 1 and 2 years after surgery was not statistically significantly different. Worsening of visual acuity by more than 2 lines was not statistically different between the groups 2 years after the surgery and at the final visit (P =0.47, P =0.60, respectively). A greater number of eyes developed endophthalmitis and were more likely to undergo subsequent tube revision in the FB-BGI group, but the differences were not significant.
Conclusions: Both incision techniques were equally effective in controlling IOP. Each surgical approach has its advantages and this study suggests that either technique may be used safely and effectively.
Introduction
Since their introduction in the 1970s, glaucoma drainage devices (GDDs) have generally been reserved for refractory cases of glaucoma. However, in the past decade, they have been used in earlier stages of glaucoma and their use has nearly quadrupled over a 10-year period. GDDs divert aqueous humor to an area remote from the limbus to promote the development of a bleb in healthier conjunctiva. Long-term success for GDDs has ranged from 50% to 88% in aphakia and or pseudophakia and from 61% to 100% in eyes with failed trabeculectomy surgery, 75 to 100% for uveitic glaucoma, 44% to 100% for developmental glaucoma, and 22% to 78% for neovascular glaucoma. Studies to date have not differentiated between the 2 conjunctival surgical approaches used when implanting this device.
The conjunctival flap created during insertion of a GDD can be limbus-based (LB) or fornix-based (FB). Each flap technique has its advantages and disadvantages. The LB incision provides better visualization during placement of the implant's plate and also results in a smoother conjunctival surface at the limbus, promoting patient comfort postoperatively. An LB incision also avoids the destruction of limbal stem cells, which may be deficient in some patients undergoing GDD surgery (eg, aniridia, chemical injury). However, surgical exposure is limited during tube insertion into the anterior chamber and extensive conjunctival scarring may preclude this type of approach. This technique also places an incision in the conjunctival fornix in close proximity to where one might expect the bleb to form, potentially affecting capsule formation and resistance to flow. In contrast, an FB incision allows easier visualization at the limbus during tube insertion and places the incision site away from the area of bleb formation; however, posterior visualization is more difficult, making placement of the implant's plate challenging unless a wide peritomy or radial relaxing incision is created.
The FB conjunctival flap is the more popular incision technique. In the tube versus trabeculectomy (TVT) study, a multicenter, randomized clinical trial designed to prospectively compare the safety and efficacy of nonvalved tube shunt surgery versus trabeculectomy with mitomycin C, 82 of 107 (77%) patients randomized to the tube group had tubes placed via an FB conjunctival flap and 25 of 107 (23%) were placed via an LB conjunctival flap technique. A comparison of outcome measures between these 2 surgical techniques was not assessed by the TVT investigators.
Capsule formation around a GDD implant results from a foreign body reaction to the implant: macrophages and giant cells accumulate at the implant surface followed by fibroblast proliferation and collagen deposition with capillary formation. Stabilization of the implant to the scleral surface, varying the timing and intensity of aqueous flow to the capsule, size and shape of the implant, and the use of antifibrotic agents are all modifications that affect capsule fibrosis and subsequent IOP control. However, it is not known whether the proximity of the conjunctival incision affects capsule fibrosis and IOP control. We therefore conducted a retrospective study to compare the effects of LB versus FB conjunctival flaps on the efficacy of IOP control after GDD surgery. We hypothesized that the intraocular pressure (IOP) would be lower in the FB approach because the incision site is placed away from the site of bleb formation.