March 2012
Volume 53, Issue 3
Free
Letters to the Editor  |   March 2012
Author Response: Morphometric Characteristics of Central Retinal Artery and Vein in the Optic Nerve Head of Patients with Diabetes
Author Affiliations & Notes
  • Dao-Yi Yu
    The Centre for Ophthalmology and Visual Science and
    the The ARC Centre of Excellence in Vision Science, The University of Western Australia, Perth, Western Australia, Australia.
  • Min H. Kang
    The Centre for Ophthalmology and Visual Science and
    the The ARC Centre of Excellence in Vision Science, The University of Western Australia, Perth, Western Australia, Australia.
  • Chandrakumar Balaratnasingam
    The Centre for Ophthalmology and Visual Science and
    the The ARC Centre of Excellence in Vision Science, The University of Western Australia, Perth, Western Australia, Australia.
  • Paula K. Yu
    The Centre for Ophthalmology and Visual Science and
    the The ARC Centre of Excellence in Vision Science, The University of Western Australia, Perth, Western Australia, Australia.
  • William H. Morgan
    The Centre for Ophthalmology and Visual Science and
  • Ian L. McAllister
    The Centre for Ophthalmology and Visual Science and
  • Stephen J. Cringle
    The Centre for Ophthalmology and Visual Science and
    the The ARC Centre of Excellence in Vision Science, The University of Western Australia, Perth, Western Australia, Australia.
Investigative Ophthalmology & Visual Science March 2012, Vol.53, 1637-1638. doi:https://doi.org/10.1167/iovs.12-9703
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      Dao-Yi Yu, Min H. Kang, Chandrakumar Balaratnasingam, Paula K. Yu, William H. Morgan, Ian L. McAllister, Stephen J. Cringle; Author Response: Morphometric Characteristics of Central Retinal Artery and Vein in the Optic Nerve Head of Patients with Diabetes. Invest. Ophthalmol. Vis. Sci. 2012;53(3):1637-1638. doi: https://doi.org/10.1167/iovs.12-9703.

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      © ARVO (1962-2015); The Authors (2016-present)

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We appreciate the interest that Dr. Dimitrova has expressed in our paper, 1 published in the March 2011 issue. 2 We agree that a detailed morphometric analysis of the central retinal artery and vein inside the optic nerve head has not been undertaken in patients with diabetes. Diabetic retinopathy remains a leading cause of blindness in the working population of developed countries. However, a general view of the pathogenesis of diabetic retinopathy is that it is a disease of multifactorial origin, with a range of microvascular and neuroglial abnormalities. We are still unable to provide sufficient solid evidence to determine the cause-and-consequence relationship and interpret how the pathologies found in experimental and clinical studies relate to one another and how they contribute to disease progression. 3,4  
There is abundant evidence suggesting early changes in retinal perfusion before the onset of diabetic retinopathy that may be related to inflammatory changes, loss of capillaries, and progressive ischemia and hypoxia. Structural and functional changes in the retinal vasculature are closely related to diabetes and diabetic retinopathy. The pathogenic role of the vascular endothelium in diabetic retinopathy is thought to be critical, as it is a vast and heterogeneous organ faced with diverse challenges. In addition to regulating vascular tone, the endothelial cells carefully balance and dynamically regulate both barrier function and selective permeability to solutes and immune cells. Endothelial cells in specific locations such as the lamina cribrosa may meet different mechanical forces, including fluid shear, hydrostatic pressure, and cyclical stretching. In pathologic conditions such as diabetes, both hemodynamic conditions and endothelial cells could be significantly altered. In previous studies, our group has attempted to quantify the morphologic, 5 pharmacologic, 6 and functional 7 changes in the ocular vasculature in the early stage in rat models of induced diabetes. We have also examined pharmaceutical interventions for ameliorating the vascular changes in induced diabetes. 8  
There is no doubt that morphologic analysis of endothelial cells from human eyes could provide valuable information toward understanding the possible pathogenic role of endothelial cells in many ocular diseases. Fortunately, the intravascular perfusion fixation and staining technique developed in our laboratory allows us to investigate the intracellular changes in the whole retinal and choroidal microvasculature and their relationship with retinal neurons and glia in normal, aging, and diseased human donor eyes. 9 We hope to gain new information from human donor eyes that will help us to further bridge the gap between the findings in experimental and clinical studies. 
We cannot overemphasize the importance of study of the pathogenesis of diabetic retinopathy, particularly the possible pathogenic roles of the retinal vasculature. Although the roles of the central retinal artery and vein in the pathogenesis of diabetic retinopathy remain unclear and the role of endothelial cell dysfunction is not well understood, in the future, as we continue to expand our collection of human donor eyes, we may well be in a position to contribute to the understanding of endothelial cell changes in diabetic human eyes and to complement the clinical study by Dimitrova et al. 10  
References
Dimitrova G . Morphometric characteristics of central retinal artery and vein in the optic nerve head of patients with diabetes (Letter). Invest Ophthalmol Vis Sci. 2012;53:1637. [CrossRef] [PubMed]
Kang MH Balaratnasingam C Yu P . Morphometric characteristics of central retinal artery and vein endothelium in the normal human optic nerve head. Invest Ophthalmol Vis Sci. 2011;52:1359–1367. [CrossRef] [PubMed]
Gariano RF Gardner TW . Retinal angiogenesis in development and disease. Nature. 2005;438:960–966. [CrossRef] [PubMed]
Curtis TM Gardiner TA Stitt AW . Microvascular lesions of diabetic retinopathy: clues towards understanding pathogenesis? Eye (Lond). 2009;23:1496–1508. [CrossRef] [PubMed]
Su EN Alder VA Yu DY Yu PK Cringle SJ Yogesan K . Continued progression of retinopathy despite spontaneous recovery to normoglycemia in a long-term study of streptozotocin-induced diabetes in rats. Graefes Arch Clin Exp Ophthalmol. 2000;238:163–173. [CrossRef] [PubMed]
Su EN Yu DY Alder VA Yu PK Cringle SJ . Altered vasoactivity in the early diabetic eye: measured in the isolated perfused rat eye. Exp Eye Res. 1995;61:699–711. [CrossRef] [PubMed]
Cringle SJ Yu D-Y Alder VA Su EN . Retinal blood flow by hydrogen clearance polarography in the streptozotocin-induced diabetic rat. Invest Ophthalmol Vis Sci. 1993;34:1716–1721. [PubMed]
Yu PK Yu DY Cringle SJ Su EN . Tetrahydrobiopterin reverses the impairment of acetylcholine-induced vasodilatation in diabetic ocular microvasculature. J Ocul Pharmacol Ther. 2001;17:123–129. [CrossRef] [PubMed]
Yu PK Balaratnasingam C Morgan WH Cringle SJ McAllister IL Yu DY . The structural relationship between the microvasculature, neurons, and glia in the human retina. Invest Ophthalmol Vis Sci. 2010;51:447–458. [CrossRef] [PubMed]
Dimitrova G Kato S Yamashita H . Relation between retrobulbar circulation and progression of diabetic retinopathy. Br J Ophthalmol. 2003;87:622–625. [CrossRef] [PubMed]
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