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Editors Selection IGR 14-4
Ocular Blood Flow: Anterior and posterior optic nerve head
Comment by Alon Harris on:
51848 Anterior and posterior optic nerve head blood flow in nonhuman primate experimental glaucoma model measured by laser speckle imaging technique and microsphere method, Wang L; Cull GA; Piper C et al., Investigative Ophthalmology and Visual Science, 2012; 53: 8303-8309
Accurately measuring the ocular circulation is essential for further elucidation of the pathophysiology of various ophthalmic diseases including glaucomatous optic neuropathy. Among the various imaging technologies currently available, each imaging device presents interesting information regarding tissue-specific ocular hemodynamics, but every device has inherent limitations. Wang and associates contribute to the increasing evidence of vascular contributions in glaucoma pathology revealing chronic intraocular pressure (IOP) elevation causes significant optic nerve head circulation decreases in an experimental glaucoma model verified by two independent techniques. The authors also reported a high correlation was reported between the circulation reduction measured by laser speckle flowgraphy (LSFG) and microsphere methods suggesting LSFG is capable of assaying blood flow in the deep ONH region. One strength of the model was the acquisition of three to five baselines of IOP, retinal never fiber layer thickness, and LSFG from both eyes of each animal. The use of two independent imaging techniques adds further value due to the specific individual limitations of each imaging method. One limitation of the current report is the limited number of
No single imaging device is capable of assessing all of the relevant ocular vascular beds in terms of the ocular circulationdata points available from a model using nine rhesus macaques. Additionally, despite strong correlation with microsphere methods, the actual meaning of LSFG mean blur rate (MBR) in terms of tissue specific blood flow is poorly understood. In balance of this approach, the authors should be commended on their addition to understanding the relationship of IOP and optic nerve head blood flow alterations in an experimental glaucoma model. While no single imaging device is capable of assessing all of the relevant ocular vascular beds in terms of the ocular circulation, careful consideration of investigations such as this helps further our understanding of the vascular component of glaucoma pathology.