Glaucoma
Table 1: Summary of the Studies Presented Study
Technique
Khairy et al., 200914 Chiselita, 200115
Bissig et al., 200816
Kozobolis et al., 200217 Guedes et al., 201018 Anand et al., 201120 Sunaric-Mégévand
and Leuenberger, 200125 Carassa et al., 20039 Lüke et al., 200226 O’Brart et al., 200427 Tanito et al., 200229 Park et al., 200530
Wishart and Dagres, 200628 Anand and Anand, 200832 Anand and Anand, 200832 Guedes et al., 201018 Grieshaber et al., 201137 Lewis et al., 201138 Lewis et al., 201138
DS DS
DSI
DSMMC DSMMC DSIMMC VC
VC VC
VCMMC PhacoVC PhacoVC PhacoVC PhacoDS
PhacoDSMMC PhacoDSMMC VCc VCc
PhacoVCc
Patients Number Definition of Achieving
of Patients
Success (%) 37 45 48 50 58 78 59
76 30 60 95 61 89 60 76 56 94 40 78
43 17 52 40
285 146 17
19 30 25 18 84 80 48 48 41 25 89 27
Success
(IOP mmHg) <22 <21 ≤21 <22 <21 <19 ≤20
≤21 <22 <21 <21 <21 ≤21 <22 <19 <21 ≤21 ≤21 ≤21
Follow-up (Years)
2
1.5 10 3 3 3 3
2 1 1 1 2 3 2 2 3 1 3 3
GP (%)
4.6
60 0
13 63 9
4.5 12 23 §
25 (5-FU) 29 (5-FU)
Post-operative 5-FU/MMC (%)
71 62 12 24
21 § (5-FU/MMC) 18 § (5-FU/MMC)
5-FU = 5-fluorouracil; DS = deep sclerectomy; DSI = DS + implant; DSMMC = DS + mitomycin C; GP = goniopuncture; IOP = intraocular pressure; MMC = mitomycin C; Phaco = phacoemulsification; VC = viscocanalostomy; VCc = VC + canaloplasty; VCMMC = VC + mitomycin C; § = plus needling procedure.
ndividual nuances. Originally, the only version of NPGS was DS. As surgical techniques have evolved, there are now several variations of the original DS. In 1980, George Spaeth10
commented on comparing
results between different surgical techniques: “This is not really surprising when one considers the vast variety of techniques entitled… trabeculectomy.” The historical term NPGS has stuck, but is no longer relevant and its use should be discouraged to avoid confusion between the different techniques. The many variations of NPGS make it difficult to compare meaningfully results of trabeculectomy surgery and between surgeons. The multiple variations in surgical technique lead to confusion, even among glaucomatologists. For example, Fyodorov is often credited as one of the fathers of NPGS, yet the operation he described, DS,11
involves a basal iridectomy. The grouping of all the ‘non-penetrating’ procedures under one term (NPGS) for reasons of simplification or comparison is as useful as grouping trabeculectomy and tube surgery under the label ‘penetrating glaucoma surgery’; it is as inappropriate as it is unhelpful. The natural evolution of NPGS has rendered the term inaccurate and obsolete.
Review of Literature on Ab Externo Canal Surgery in the Context of Open-angle Glaucoma We have identified several significant permutations in surgical techniques that may lead to a difference in outcome and have analyzed them separately. There are two broad categories: the deep sclerectomies and the viscocanalostomies. As explained by Mendrinos et al.,12
Schlemm’s canal, with no subconjunctival drainage. A viscoelastic is injected into the cut ends of Schlemm’s canal and the sclera is sutured down tightly, to prevent aqueous egress – unlike in DS where the superficial scleral flap is sutured loosely or not at all.
In DS, some surgeons use collagen and/or hyaluronic acid implants to prolong success rates and/or antimetabolites to achieve lower post-operative IOPs. These groups are all examined separately. In VC, we have differentiated between tight scleral closure, as per Stegmann’s original paper,13
and loose closure aiming for
subconjunctival drainage. Both DS and VC have been combined with cataract extraction, with further separation in this article for analytical purposes. More recently, VC has been combined with canaloplasty, which again is discussed separately.
Nd:YAG laser goniopuncture (GP) rates and post-operative use of antimetabolites are included where published.
in DS, the aqueous is designed to drain subconjunctivally – as in trabeculectomy surgery. The main advantages are reduced hypotony in the immediate post-operative period, lower risk of endophthalmitis, and less inflammation (from not entering the anterior chamber and not performing a peripheral iridectomy). VC aims for aqueous flow along
28
In an attempt to reduce inter-publication heterogeneity, we have stuck to ‘complete success rates’ as a definition of success, i.e., tonometric success achieved without topical hypotensive medications. As several tonometric definitions of success have been used, for homogeneity, we have used the following: <19 mmHg; <20 mmHg; ≤21 mmHg; <22 mmHg. To obtain an idea of surgical durability, only studies with more than 12 months follow-up have been included. Study endpoints have only been included where the numbers of participants reaching that particular endpoint have been published. The only implants examined are the more commonly used SKGel™ (Corneal, France) and AquaFlow™ (STAAR, Switzerland). A summary of all the studies in this paper is presented in Table 1.
US OPHTHALMIC REVIEW
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