TAG Sandwich Technique- Novel Single-Stage Scleral Reinforcement for glaucoma drainage

This article published by Faisal Ahmed and Nada G. Mohamed described a novel TAG sandwich technique to strengthen scleral thinning and implant glaucoma drainage device in a single-staged operation. Pericardial tutoplast was used for scleral reinforcement of thin sclera ("bottom layer of sandwich") followed by implantation of a GDD on top of the scleral reinforcement ("middle tube layer of sandwich") followed by gluing of another pericardial TutoplastTm graft on top of the tube ("top layer of sandwich"), in a complex case of refractory primary open-angle glaucoma with generalized thin sclera.

Case Report

The patient was a 29-year-old lady with Ehler-Danlos syndrome, with uncontrolled advanced open-angle glaucoma. She had previously lost vision in the right eye after an unsuccessful retinal detachment repair. Her only seeing left eye had thinned blue sclera which was considered to be an ocular manifestation of Ehler-Danlos syndrome.

Other ocular features that were present in this case included bilateral microcornea, which was reported with Ehler-Danlos type VI but to a lesser extent than Keratoglobus. The patient also has pathological myopia which is also seen in Ehler-Danlos patients.

Despite maximum medical therapy, and attempted micropulse cyclophotocoagulation (to avoid intraocular surgery), her intraocular pressure remained uncontrolled. Her IOP maintained at 26 mmHg on full topical intraocular pressure-lowering drops, in addition to oral: acetazolamide 250 mg three times a day, and unfortunately, the patient was symptomatic with deteriorating visual fields and vision.

The patient's axial length in this eye was 29.84 mm, and horizontal corneal diameter as shown by white-to-white measurement was 9.83 mm. Her visual acuity preoperatively was 6/36, with a refraction of -11.75 sphere and -1.00 cylinder axis 95 degrees. Her central corneal thickness was 443 microns (thin cornea), and she had grade 4 on Van Herick and AC depth of 3.04 mm as evident from her biometry.

Other Ehler-Danlos-related systemic manifestations in patient included mitral valve prolapse, which reduced her ASA (American Society of Anesthesiologists classification) rating. The decision was made to implant a glaucoma drainage device. However, scleral reinforcement was required as generalized blue sclera made tube implant challenging.

Although the senior author FA had already described a two-step procedure of scleral reinforcement with pericardial TutoplastTm surgery initially with glaucoma tube implant as a second procedure 1 month later, this would have meant 2 anesthetics and delay in IOP control. Therefore, it was decided to perform a one surgery scleral strengthening and tube surgery—using the "TAG sandwich technique" under general anesthetic.

The first part of the procedure consisted of a superior peritomy, a 7/0 silk corneal traction suture was used to enhance visualization, and care on taking the suture was made to allow enough depth and not too much traction to avoid cheese wiring of the suture. Reinforcement of the existing thin sclera ("bottom layer of sandwich") from the limbus with a double layer of pericardial TutoplastTm was then performed, and the TutoplastTm was glued onto the sclera with Tisseel fibrin sealant. The sclera under the plate was also reinforced by gluing a single layer of pericardial TutoplastTm to it as a precaution.

The second part of the procedure was to place a (nonvalved) BaerveldtR BG 101-250 GDD over the TutoplastTm ("middle tube layer of sandwich"), and the plate was then sutured successfully to an area of sclera that did not show thinning on visualization using 9/0 Prolene suture on a spatulated needle. This was to ensure the plate was secured in place and minimize its movement. The tube was fixed to the TutoplastTm to avoid perforating the sclera as the rest of the anterior sclera showed bluish discoloration and thinning.

The GDD lumen was occluded via a 3/0 Supramid suture to avoid postoperative hypotony, and the tube was inserted into the anterior chamber through a superotemporal limbal tunneled incision. The free end of the Supramid suture was then tucked to the inferior fornix. Another double layer of pericardial TutoplastTm was glued over the tube, and the conjunctiva was placed over the graft ("top layer of patch graft tube sandwich"). Conjunctival closure was achieved via suturing and gluing at the limbus only.

Postoperatively, the intraocular pressure was controlled by full topical intraocular pressure-lowering drops, in addition to systemic acetazolamide, until the Supramid suture was removed 6 weeks after the original surgery to allow for the formation of the fibrous capsule around the tube to avoid hypotony.

This was performed by instilling topical anesthesia, making a small conjunctival incision with Westcott scissors at the free edge of the Supramid suture which was placed in the inferior bulbar conjunctiva. Once the free end of the Supramid was exposed, the whole suture was held with Moorfield forceps and pulled out. The patient had completed 11 months of follow-up, her intraocular pressure was controlled at 7 mmHg on no intraocular pressure-lowering medications, her pinhole vision was 6/36 in that eye before posterior subcapsular cataract started to develop, for which the patient underwent a cataract surgery about a year after her tube surgery, and her current best corrected vision was 6/24.

In this refractory glaucoma patient with thinned sclera who required a glaucoma drainage device to control her intraocular pressure, it was important to strengthen the sclera below the GDD to reduce the risk of scleral perforation.

Another solution to avoid the need for scleral reinforcement is to find areas of more normal sclera and thus change the usual supertemporal site of GDD implantation; however, inferior placed tubes carry increased risk of exposure, which may increase the risk of endophthalmitis. In particular, this patient had generalized scleral thinning, and there was no advantage to position the GDD elsewhere as scleral reinforcement was required wherever authors had placed the GDD.

"Our combined "TAG sandwich" technique allowed most of the suturing to be into the TutoplastTm avoiding suturing directly into the sclera, ensuring safe plate fixation. A two-staged procedure was described earlier by the senior author FA in cases with scleral thinning, to achieve scleral strengthening. This novel combined procedure has the advantage of minimizing the number of procedures required under general anesthetic and implanting the GDD immediately for more timely intraocular pressure control.

We believe our combined "TAG sandwich" technique provides another option in high-risk refractory glaucoma patients with thin sclera or scleromalacia who require filtration surgery. This procedure allowed a safe and effective outcome for our young refractory glaucoma patient with generalized scleral thinning in one surgery, avoiding complications associated with multiple surgeries as well as systemic risks."

Source: Hindawi Case Reports in Ophthalmological Medicine Volume 2021

https://doi.org/10.1155/2021/6698919