Transcorneal erbium laser sclerostomy: towards a guarded laser sclerostomy technique.

PURPOSE

To attempt transcorneal laser sclerostomy with the erbium laser and to control the flow of aqueous through this sclerostomy with a suture ligature.

METHODS

A contact erbium laser was used to create sclerostomies through small corneal incisions in both eyes of eight rabbits. Prior to surgery, a Merocel sponge soaked in mitomycin-C (0. 4 mg/cc) was applied to the conjunctiva at the operative site in one eye of each rabbit for 5 min. In the perfused human autopsy eye, following the creation of transcorneal erbium laser sclerostomy, a ligature suture was placed at the limbus around the sclerostomy opening to limit fluid flow.

RESULTS

Using the erbium laser probe and the transcorneal approach, patent sclerostomies were created in all eyes. Intraocular pressures were significantly lower in mitomycin-C-treated eyes up to four months postoperatively (p = 0. 05). Eyes not treated with mitomycin-C demonstrated failure of filtering blebs by 1 month postoperatively (mean bleb survival = 9. 3 days). All mitomycin-C-treated eyes showed evidence of bleb formation up to 4 months postoperatively. Histologic examination of transcorneal sclerostomies in rabbit eyes showed patent sclerostomies at 1 day postoperatively with minimal adjacent thermal damage. In perfused human autopsy eyes, intraocular pressure was maintained near preoperative levels following placement of a ligature suture around the sclerostomy and decreased with release of the suture.

CONCLUSIONS

These results demonstrate that functional filtering blebs can be created via small transcorneal incisions using the erbium laser. Transconjunctival mitomycin-C produces lower postoperative intraocular pressures and prolongs bleb survival. Aqueous flow through the sclerostomy was controlled with a suture ligature.