Gábor Holló and Andreas Katsanos
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Selective laser trabeculoplasty (SLT) employs a frequency-doubled Q-
switched Nd-YAG laser to deliver low energy in brief pulses with a large spot
diameter (400μm) to the surface of the trabecular meshwork [72]. The precise
mechanism by which SLT enhances aqueous humor outflow remains
unknown. SLT is considered to selectively target the pigmented trabecular
meshwork cells without causing obvious coagulative or disruptive changes.
Therefore the technique can be repeated in eyes previously treated with ALT
or SLT [72,73].
In eyes with POAG, the efficacy of SLT has been found similar to that of
ALT [73]. However, there is limited information on the comparative efficacy
of SLT and ALT in XFG. A 6-month randomized trial evaluated the efficacy
of SLT versus ALT on 76 inadequately controlled XFG eyes and XFS eyes
with ocular hypertension [74]. SLT and ALT resulted in similar IOP
reductions (6.8 mmHg and 7.7 mmHg, respectively, P=0.56) from the
corresponding pre-laser baseline values (SLT: 23.1 mmHg, ALT: 25.2 mmHg,
P=0.03). Moreover, an identical proportion of patients (73%) achieved at least
20% IOP reduction with either treatment at the 6-month post-laser visit. Other
reports suggest that XFG and POAG eyes respond to SLT similarly both when
the procedures are used as primary [75] or adjunctive [76,77] interventions.
It is important to note that ALT and SLT are seldom adequate treatments
for patients with high-pressure XFG, especially when considering that a low
target IOP (<17 mmHg) is needed to prevent progression on the long term
[25]. Nonetheless, these techniques can be considered in elderly XFG patients
with suboptimal compliance, in XFG patients intolerant to medical therapy
and in XFG patients who are poor candidates for filtration surgery.
Surgical Treatment
Glaucoma surgery is mainly reserved for eyes insufficiently controlled
with medical and/or laser treatment; cases in which progression develops on
maximal tolerated medical and laser treatment; and in patients intolerant or
non-compliant to medical therapy. For several years trabeculectomy (typically
with adjuvant 5-fluorouracil or mitomycin C) has been considered the gold
standard surgical procedure in XFG [78,79]. Evidence suggests that the long-
term survival of trabeculectomy in XFG may be longer than that in POAG
[78,80,81], and glaucomatous progression after filtering surgery may be
slower in XFG patients compared to POAG patients [19,81].