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addition to the worse IOP characteristics in eyes with XFG, the purported
elastosis-induced biomechanical alterations of the lamina cribrosa that may
render the optic nerve more vulnerable to effects of IOP elevation are thought
to underlie the poorer long-term prognosis compared to POAG [15,16,23,25].
It should be noted that gradual or sudden IOP elevation in treated and
seemingly well-controlled eyes with XFG may occur. Thus, close follow-up
over the long term is necessary even in apparently well-controlled XFG
patients [3,19]. A notable difference between XFG and POAG is that the
former is not associated with a higher risk of IOP elevation following steroid
treatment [47].
Medical Treatment
Because XFG is a high-pressure glaucoma with unpredictable
characteristics (e.g., high spikes outside office hours), achieving a sufficiently
low IOP throughout the 24-hour cycle is frequently difficult [23,44,45].
Medical therapy should ideally be tailored to the particular needs of eye in
XFG [48,49]. Prostaglandin analogues are common first choices in open-angle
glaucoma due to their efficacy, convenient once-daily administration and
favorable safety profile [50-52]. A 3-month, multicenter, single masked,
prospective, parallel group study with XFG patients compared the diurnal
efficacy of evening-dosed latanoprost 0.005% versus timolol 0.5%
administered twice daily [53]. The authors found that latanoprost provided
marginally superior diurnal IOP reduction and smaller IOP fluctuation
compared to timolol. Although the efficacy difference between latanoprost
(reduction from untreated baseline 24.9 mmHg to 17.4 mmHg) and timolol
(reduction from untreated baseline 24.7 mmHg to 18.3 mmHg) for the diurnal
IOP did not reach statistical significance (P=0.07), the IOP reduction at the 8
a.m. time-point was significantly greater with latanoprost (-8.5 mmHg vs. -6.0
mmHg).
The investigators of a 6-month, single masked, prospective, parallel group
study with IOP measurements at 8 a.m., 10 a.m. and 4 p.m. compared the IOP
lowering efficacy of evening-dosed latanoprost 0.005% and travoprost 0.004%
and the dorzolamide 2%/timolol 0.5% fixed combination dosed twice daily, in
patients with XFG [54]. The mean untreated daytime IOP in all groups varied
between 23.8 mmHg and 25.7 mmHg and the mean IOP reduction was 8.2
mmHg for latanoprost, 9.3 mmHg for travoprost and 11.5 mmHg for the
dorzolamide/timolol fixed combination. This result, however, may not be