Trabeculectomy is one of the standard surgical methods used to treat glaucoma by creating a drainage pathway for aqueous humor from inside the anterior chamber of the eye to the outside through a newly created opening at the junction of the cornea and sclera. A scleral tissue flap covers the outlet like a door before the aqueous humor drains into the subconjunctival space, appearing as a bleb on the surface of the eye (Figure 1). Some of the fluid in the bleb seeps through the conjunctiva to the outside, mixing with tears, and is eventually absorbed by blood vessels, conjunctival tissues around the vessels, and lymphatic vessels.
Trabeculectomy can reduce intraocular pressure by draining a large amount of fluid at once, allowing for rapid pressure reduction from during surgery to after surgery.
Purpose of trabeculectomy surgery
The purpose is to create a new drainage pathway for aqueous humor when natural drainage is blocked or insufficient, causing the existing glaucoma to worsen.
Indications for trabeculectomy surgery include
- Full treatment with eye drops and/or oral medications to reduce intraocular pressure combined with laser therapy has been applied, but the pressure cannot be controlled to the desired level or the disease progression cannot be slowed.
- The patient is unable to use glaucoma eye drops.
- The patient does not use glaucoma eye drops as prescribed or inconsistently.
- There are side effects in the eyes and/or systemic side effects caused by glaucoma medications.
Goals of trabeculectomy surgery
The goal is to create a drainage pathway that allows an appropriate amount of aqueous humor outflow and to maintain postoperative intraocular pressure that is neither too high nor too low, suitable for the severity of glaucoma in each patient, and to slow the disease progression (degeneration or death of retinal ganglion cells and the optic nerve).
Success of trabeculectomy surgery
Success depends not only on the created opening for aqueous humor drainage from the anterior chamber and the absorption capacity of the bleb on the eye surface but also on surgical techniques and methods to reduce scarring at the surgical site during and after surgery.
There is evidence that 5-Fluorouracil (5-FU) and Mitomycin C (MMC) can help reduce scarring and increase the success rate of trabeculectomy surgery. Some studies have found that Mitomycin C reduces intraocular pressure more effectively than 5-Fluorouracil. Therefore, these agents are routinely used during and/or after trabeculectomy surgery.
In addition to 5-Fluorouracil and Mitomycin C, other devices or substances have been developed to improve surgical success, such as Ologen (ProSys, London, UK), a collagen material derived from pigs used as an implant between tissue layers during surgery and is biodegradable (Figure 2), or Healaflow (Aptissen, Geneva, Switzerland), a special densely cross-linked hyaluronic acid (reticulated hyaluronic acid) gel that is clear and viscous, allowing aqueous humor to flow through and drain normally (Figure 3).
The use of additional devices or substances beyond 5-Fluorouracil and Mitomycin C depends on the surgeon’s discretion and must be considered on a case-by-case basis.
Figure 1 shows a bleb appearing on the surface of the eye and above the cornea (11-1 o’clock) after trabeculectomy surgery combined with Mitomycin C, which is the standard surgical method for glaucoma.
Figure 2 shows a bleb appearing on the surface of the eye and above the cornea (10-2 o’clock) after trabeculectomy surgery combined with Mitomycin C and Ologen, which is placed on the sclera (episclera) and under the conjunctiva.
Figure 3 shows a bleb appearing on the surface of the eye and above the cornea (10-2 o’clock) after deep sclerectomy surgery, which is another standard surgical method for glaucoma, combined with Mitomycin C and Healaflow.
