December 2010
Volume 51, Issue 12
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Letters to the Editor  |   December 2010
Linear Relation between Structure and Function
Author Affiliations & Notes
  • Aharon Wegner
    Glaucoma Service, Department of Ophthalmology, Klinikum rechts der Isar, Technische Üniversität München, München, Germany.
  • Alexander Erben
    Glaucoma Service, Department of Ophthalmology, Klinikum rechts der Isar, Technische Üniversität München, München, Germany.
Investigative Ophthalmology & Visual Science December 2010, Vol.51, 6891. doi:10.1167/iovs.09-4628
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      Aharon Wegner, Alexander Erben; Linear Relation between Structure and Function. Invest. Ophthalmol. Vis. Sci. 2010;51(12):6891. doi: 10.1167/iovs.09-4628.

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

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The main limitation of the study by Danesh-Meyer et al. 1 was neither discussed nor mentioned. The time axis was not taken into account. The functional change after an acute event such as anterior ischemic optic neuropathy (AION) is immediate, but there is a delay before the anatomic changes take place. In this study, most of the patients with nonarteritic anterior ischemic optic neuropathy (NAION) or arteritic anterior ischemic optic neuropathy (AAION) were tested a short period after the acute event, as described by the authors. 
In a similar study by Hood et al., 2 the patients were tested at least 5 months after the AION event, with a median of 2.95 years. The reason was to allow sufficient time to minimize the effects of optic disc swelling and to allow the retinal ganglion cell (RGC) axons to degenerate. The results of the study in Hood et al. are obviously contrary to those presented by Danesh-Meyer et al. The relationship between a structure (optical coherence tomography [OCT]–determined retinal nerve fiber layer thickness) and function (standard automated perimetry [SAP]–determined sensitivity loss) is the same in patients with AION as in those with open angle glaucoma (OAG). 
It is not adequate to use visual field perimetry results as a criterion for comparison in the population examined by Danish Meyer et al., 1 as visual acuity and visual fields improve up to ∼6 months from the onset of NAION. 3  
The only conclusion that can be made from the results of Danish-Meyer et al. 1 is that a few months after the acute event of NAION/AAION the optic disc and RNFL look different than they do in OAG. 
References
Danesh-Meyer HV Boland MV Savino PJ . Optic disc morphology in open angle glaucoma compared with anterior ischemic optic neuropathies. Invest Ophthalmol Vis Sci. 2010;51:2003–2010. [CrossRef] [PubMed]
Hood DC Anderson S Rouleau J . Retinal nerve fiber structure versus visual field function in patients with ischemic optic neuropathy: a test of a linear model. Ophthalmology. 2008;115:904–910. [CrossRef] [PubMed]
Hayreh SS Zimmerman MB . Non-arteritic anterior ischemic optic neuropathy: role of systemic corticosteroid therapy. Graefes Arch Clin Exp Ophthalmol. 2008;246:1029–1046. [CrossRef] [PubMed]
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