Transciliary fistulization, also known as transciliary filtration or Singh filtration, uses a thermocauterization device called the Fugo blade to create a pore in the posterior chamber of the eye from the sclera through the ciliary body. This procedure reduces intraocular pressure (IOP) in patients with glaucoma by allowing aqueous fluid to seep into the subconjunctival lymphatic system.
Glaucoma is a disease characterized by degeneration of the optic disc. Elevated intraocular pressure has long been thought to be the primary etiology, but the relationship between IOP and optic nerve damage varies among patients, suggesting a multifactorial origin. For example, some patients with clearly elevated IOP will show no damage to the optic nerve, while other patients with marginal or no pressure elevation will, nonetheless, show optic nerve damage. The association between glaucoma and other vascular disorders, such as diabetes or hypertension, suggests vascular factors may play a role in glaucoma. Specifically, it has been hypothesized that reductions in blood flow to the optic nerve may contribute to the visual field defects associated with glaucoma.
For primary-open angle glaucoma (POAG) associated with IOP, a decrease in aqueous outflow through the trabecular meshwork is believed to cause the IOP. However, there are many theories on what causes the decrease in aqueous outflow such as foreign body obstruction, trabecular endothelial cell loss, reduced trabecular pore density, disturbances in neurofeedback mechanisms, or normal phagocytic activity.
IOPs above 21 mm Hg have been shown to increase rates of visual field loss, and conventional management of the patient principally involves drug therapy to control elevated IOP to prevent or delay glaucomatous loss of vision. For POAG, drug therapy may include alpha-agonist, beta-blockers, carbonic-anhydrase inhibitors, miotic agents, and prostaglandin analogs. When the maximum tolerated medical therapy fails to control optic neuropathy, surgical care is considered the next treatment option. Surgical procedures include laser trabeculoplasty, incisional or filtering surgery, such as trabeculectomy or drainage implants, and as a last resort, ablation of the ciliary body.
Transciliary fistulization for the treatment of glaucoma, also known as transciliary filtration or Singh filtration, is a recent approach to filtering surgery. This procedure uses a thermocauterization device called the Fugo blade to create a plasma-ablated pore or filter track from the sclera through the ciliary body to allow aqueous fluid to ooze into the subconjunctival lymphatics from the posterior chamber (behind the iris) of the eye. Plasma ablation with the Fugo blade allows the highly vascular ciliary body to be penetrated with little or no bleeding.
Transciliary fistulization allows aqueous fluid to drain from the posterior chamber of the eye and differs from conventional filtering surgeries, such as trabeculoplasty, trabeculectomy, and drainage implant surgery, in which aqueous fluid is filtered from the anterior chamber of the eye. In the trabeculoplasty procedure, a laser is used to burn small areas of the trabecular meshwork, where normal drainage of the eye occurs, to increase aqueous fluid outflow, thereby lowering IOP. In trabeculectomy (or glaucoma filtration procedure), a portion of trabecular meshwork is surgically removed through a superficial flap of sclera to lower IOP by creating an alternate pathway for the aqueous fluid to flow from the anterior chamber to a bleb created in the subconjunctival space. If trabeculectomy has failed to reduce IOP sufficiently or a patient is considered to be at high risk for trabeculectomy failure, drainage implant surgery may be considered in which a tube is placed in the anterior chamber to shunt aqueous fluid to the subconjunctival space and lower IOP. Both trabeculectomy and drainage implant surgery often result in flat or collapsed anterior chambers and usually require that an iridectomy (placement of a hole in the iris) also be performed. Transciliary fistulization rarely requires an iridectomy and is thought to reduce tissue damage and risk of scarring and other complications associated with trabeculectomy and drainage implant surgery.
The Fugo blade (Medisurg, Ltd.) for glaucoma was given U.S. Food and Drug Administration (FDA) 510(k) marketing clearance in October 2004 for sclerostomy for the treatment of primary open-angle glaucoma for which maximum tolerated medical therapy and trabeculoplasty have failed.