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Editors Selection IGR 16-4

Clinical Forms of Glaucoma: Circadian IOP and blood-flow rhythms

Comment by Kaweh Mansouri on:

59909 The circadian changes of intraocular pressure and ocular perfusion pressure after tafluprost compared with travoprost in normal tension glaucoma, Shin J; Lee JW; Choi BS et al., Journal of Ocular Pharmacology and Therapeutics, 2014; 30: 803-809

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The Low-pressure Glaucoma Treatment Study showed that a lower mean ocular perfusion pressure (OPP) was associated with progression in patients with normal tension glaucoma (NTG). Despite a plethora of data comparing different prostaglandin analog (PGA) drops to each other, 24-h data on OPP-effects are scarce. Shin et al. compare the circadian efficacy profile of tafluprost, a newer member of the PGA family, to travoprost. Using a randomized crossover design, 24-h IOP and OPP data are presented form 41 NTG patients. A limitation of the study is the absence of data on corneal thickness changes after therapy and the potential confounding effect of IOP measurements between the two drugs.

The authors show that both medications were effective in lowering IOP and increasing OPP throughout the day and night. However, travoprost showed greater efficacy than tafluprost in the 10 AM to 8 PM period. The reasons for this difference are unknown but the authors speculate that the three fluorine atoms of travoprost (vs. two for tafluprost) may offer greater metabolic stability and bioavailibility and translate into the observed diurnal difference.

Is that difference of any clinical relevance? Unfortunately, no data are available regarding the chronobiological effects of IOP on glaucoma progression. Are there specific moments of the day when IOP-lowering is more beneficial than others? Should we individualize the timing of drop application instead of the current rigid schedules? Answering these questions requires prospective therapeutic studies using continuous 24-h IOP monitoring.

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