terminology and guidelines for glaucoma ii - Kwaliteitskoepel

3.6.2 - NON PENETRATING GLAUCOMA SURGERY
These techniques have recently been advocated as operations for primary open-angle glaucoma. Two different modifications
are presently used as “non-penetrating” surgery 106-111 .
3.6.2.1 - Deep sclerectomy 111-123
In this technique, a deep lamella of corneosclera underneath the scleral flap is excised thus removing the outer wall
of Schlemm’s canal. The outer layer of the inner wall of Schlemm’s canal is frequently also removed. Percolation of
aqueous occurs through the porosity of the remaining trabecular meshwork, possibly through microperforations.
When the scleral flap is repositioned, a “scleral lake” is created. A collagen implant or a hyaluronic acid device is
often used to keep this scleral lake patent. Usually a filtration bleb forms; long-term IOP control was reported to be
less effective than with trabeculectomy 129 .
3.6.2.2 - Viscocanalostomy
In this technique hyaluronic acid is injected into Schlemm’s canal. The mechanism claimed to increase the outflow is
the widening of Schlemm’s canal and of the collector channels as well as diffusion of aqueous from the “scleral
lake” 124-130 .
3.6.3 - METHODS OF PREVENTING FILTERING BLEB SCARRING
3.6.3.1 - Antimetabolites
(See also Ch. 3.7 and FC XIII)
Antimetabolites such as 5-Fluorouracil (5-FU) and Mitomycin-C (MMC) are now used frequently in patients undergoing
glaucoma filtration surgery in order to reduce scarring and improve drainage. The use of these substances is
being refined, following the outcome of several studies. Indications and technique needs to be carefully adhered
to 131 . Risk factors for scarring include previous ocular surgery, long-term topical medications particularly those that
cause a red eye 35,132 , young age, black race, uveitis, neovascular glaucoma and others. The risk of corneal epithelial
erosions, epitheliopathy, late hypotony, bleb leaks and bleb infections must be considered. New compounds are
being investigated to more specifically target the biological processes causing excessive scarring, with the aim of
reducing complications 133 .
3.6.3.2 - Alternative methods of preventing filtering bleb scarring
Irradiation
Irradiation by various types of radiation was used during the 1970s and has proven to be effective. However, longterm
effects on the lens and on the retinal vessels (radiation retinopathy) have to be considered.
Photodynamic therapy
A dye is injected subconjunctivally at the site of operation, resulting in incorporation of the dye into the fibroblasts
of the filtering bleb area. A blue light is then irradiated that will selectively destroy the fibroblasts.
Inhibition of growth factors
Recently, attention has been turned to the role of cytokines in the process of wound healing. TGFß2 has been identified
as a probable key cytokine in post trabeculectomy wound healing. Human monoclonal anti-TGFß2 antibodies
are being tested and pilot studies have shown promising results 133 . Other approaches are also considered such as
TGFß2 anti-sense nucleotides, suramine and others.
Ch. 3 - 35 EGS