Glaucoma Marc Töteberg-Harms, MD,1,2
Endoscopic Goniotomy Peter P Ciechanowski, MD,2
and Jens Funk MD, PhD3
1. Research Fellow, Massachusetts Eye and Ear Infirmary, Harvard Medical School; 2. Resident, Department of Ophthalmology, UniversityHospital Zurich; 3. Professor, Department of Ophthalmology, UniversityHospital Zurich
Abstract
Usually an elevated drainage resistance is responsible for elevated intraocular pressure (IOP) in glaucoma, while aqueous humor production is still normal. Therefore, currently there are great efforts to develop surgical techniques that enhance the conventional outflow through the trabecular meshwork and Schlemm’s canal and into the episcleral veins. One of these techniques is excimer laser trabeculotomy (ELT). ELT is easy to perform at the end of cataract surgery. The duration of cataract surgery is only prolonged by 2–3 minutes. IOP can be reduced by up to 34.7 %. It is known that the effect of IOP reduction is constant over time, unlike argon or selective laser trabeculoplasty. The procedure is also very safe. If required later, filtering surgery is not compromised because there is no conjunctival touch during ELT and therefore no scarring of the conjunctiva is induced. For a selected cohort of glaucoma patients, this procedure may avoid the need for trabeculectomy.
Keywords
Glaucoma, glaucoma surgery, trabecular meshwork, phacoemulsification, excimer laser trabeculotomy, excimer laser trabeculostomy, phaco-excimer laser trabeculotomy, trabecular outflow, goniopuncture, goniotomy
Disclosure: The authors have no conflicts of interest to declare. Received: October 15, 2011 Accepted: January 15, 2012 Citation: US Ophthalmic Review, 2012;5(1):33–6 Correspondence: Jens Funk, MD, PhD, Department of Ophthalmology, UniversityHospital Zurich, Frauenklinikstrasse 24, 8091 Zurich, Switzerland. E:
jens.funk@usz.ch
Glaucoma is a chronic and progressive neurodegenerative disorder causing loss of retinal ganglion cells and their axons.6 Characteristic ‘cupping’ of the optic disc is seen with corresponding loss of visual field. Elevated intraocular pressure (IOP) is a causative risk factor for the development and progression of glaucoma, and lowering IOP is the mainstay of treatment. Besides IOP, other risk factors are well-known, e.g. age, family history, and race (e.g. African descent).7
Glaucoma is a leading cause of preventable and irreversible blindness.1–5
The balance of aqueous humor production (inflow) and drainage (outflow) determines the IOP. The pathophysiology of elevated IOP in primary open-angle glaucoma (POAG) is dysfunctional drainage, specifically through the trabecular meshwork (TM).8,9
The exact mechanisms that
control drainage through the TM are not fully understood, but changes in the extracellular matrix (ECM) are one of the reasons. Furthermore, pathological accumulations of certain ECM structures within the TM have been described as causative in eyes with POAG.
In managing glaucoma patients, lowering the IOP is the only available treatment with a significant body of supporting evidence.10–20 reduction of IOP is the first line of therapy in most cases.12,21,20
Medical If medical
treatment fails, there are several well-established surgical procedures to reduce IOP.
Trabeculectomy (TE) as it is performed today was introduced in 1968 by Cairns23
and at the same time by Linner.24 © TOUCH BRIEFINGS 2012 It is still the gold standard in
glaucoma surgery. The aqueous flows via a scleral flap from the anterior chamber into the subconjunctival space.25 long-term IOP reduction.26,27
provides an even better long-term success.28–34
The greatest outflow resistance is at the location of the juxtacanalicular TM (JCT) and inner wall of Schlemm’s canal. Schlemm’s canal communicates with the episcleral veins. The drainage of aqueous outflow through the TM into Schlemm’s canal and later on into the episcleral veins is called the trabecular outflow (83–96 %, ‘conventional’ pathway), the remaining 5–15 % of the aqueous humor is drained via the uveoscleral pathway (‘alternative’ pathway).35,36
The JCT region, which includes the inner wall of
Schlemm’s canal and the underlying TM, is thought to be the region where regulation of aqueous humor outflow takes place.37–39
The JCT region
has the highest resistance to outflow, especially under conditions of elevated IOP.39–42
Although TE remains the mainstay of surgical glaucoma treatment, it remains feasible to enhance aqueous outflow through the conventional pathway. Several surgical approaches have been tried, e.g. ab interno TE with the Trabectome™,43,44
performed with or without endoscopy.
This paper focuses on another technique, excimer laser trabeculotomy (ELT, also known as excimer laser trabeculostomy). First, goniotomy and goniopuncture are discussed briefly.
33
TE is very effective in The use of antimetabolites during surgery
goniotomy, and goniopuncture, which can be
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