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Editors Selection IGR 11-4
Bloodflow: Effect of PG and B-blocker on bloodflow
Comment by Alon Harris on:
24992 Changes in optic nerve head blood flow induced by the combined therapy of latanoprost and beta blockers, Sugiyama T; Kojima S; Ishida O et al., Acta Ophthalmologica, 2009; 87: 797-800
Over the past several decades there has been a surge of new evidence suggesting ocular blood flow and perfusion pressure deficits are linked to glaucomatous optic neuropathy.1 Understanding how various hypotensive therapies influence the ocular circulation, in addition to (or as a consequence of) intraocular pressure (IOP) reduction, is becoming an important consideration in glaucoma management. To this end, Sugiyama et al. (1509) present an important and interesting study on the effects of combined therapy with latanoprost and beta blockers on optic nerve head (ONH) blood flow (laser speckle flowgraphy) in 15 normal-tension glaucoma patients. The authors found topical latanoprost-carteolol therapy increased ONH blood flow (p < 0.01), unlike latanoprost-timolol therapy. They suggest that because ocular perfusion pressure was unchanged and IOP reduction was similar, direct vasodilative effects may be indicated with carteolol. These results agree with Montanari et al.,2 but are in contrast with Sato et al., which found non-selective beta-blocker-treated eyes (timolol and carteolol) decrease blood flow and increase vascular resistance.3 Steigerwalt et al. also previously found carteolol and timolol to have similar affects in the central retinal artery which was not measured in the current investigation.4 Several methodological limitations limit comparisons including patient populations, treatment duration and hemodynamic assessment methodologies. This highlights a limitation of the current study as only laser speckle flowgraphy was utilized precluding insight into how these medications may affect the multiple vascular beds of the eye. Therefore a blood flow steal phenomenon from other tissues cannot be ruled out. Additionally, the authors do not provide a statistical power calculation for their use of only 15 eyes in this analysis. One strength of the current investigation is the exclusion of systemic vasoactive medications in the patient population which could confound the study data.
Currently, no single ocular blood flow methodology is capable of assessing all of the vascular tissues relevant in glaucoma.1 Standardization of imaging methods and comprehensive blood flow evaluation are essential for accurate comparisons of studies and meaningful insight into the vascular role in glaucoma.
References
- Weinreb RN, Harris A. The Sixth Consensus Report of the World Glaucoma Association. Kugler Publications: Amsterdam, The Netherlands 2009; pp. 161-163.
- Montanari P, Marangoni P, Oldani A, Ratiglia R, Raiteri M, Berardinelli L. Color Doppler imaging study in patients with primary open-angle glaucoma treated with timolol 0.5% and carteolol 2%. Eur J Ophthalmol 2001; 11: 240-244.
- Sato T, Muto T, Ishibashi Y, Roy S. Short-term effect of beta-adrenoreceptor blocking agents on ocular blood flow. Curr Eye Res 2001; 23: 298-306.
- Steigerwalt RD Jr, Laurora G, Belcaro GV, Cesarone MR, De Sanctis MT, Incandela L, Minicucci R. Ocular and retrobulbar blood flow in ocular hypertensives treated with topical timolol, betaxolol and carteolol. J Ocul Pharmacol Ther 2001; 17: 537-544.
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