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Donald C. Hood, Ali S. Raza, Carlos G. De Moraes, Chris A. Johnson, Jeffrey M. Liebmann, Robert Ritch; Glaucomatous Damage of the Macula as Revealed by Averaging Optical Coherence Tomography Data. Invest. Ophthalmol. Vis. Sci. 2012;53(14):665.
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© ARVO (1962-2015); The Authors (2016-present)
To better understand the nature of glaucomatous damage, we averaged the thickness maps of the inner retinal layers obtained with frequency domain optical coherence tomography (fdOCT) from healthy controls and patients with glaucoma.
FdOCT macular and optic disc cube scans were obtained from 54 eyes of 54 individuals (53.2 yrs) with healthy vision and 156 eyes of 113 patients (55.7 yrs) with glaucomatous optic neuropathy. The patients’ eyes were grouped both by mean deviation (MD) and by hemifield classification using standard categories based upon 24-2 visual fields. Retinal nerve fiber (RNF) and retinal ganglion cell plus inner plexiform (RGC+) layers were segmented with a hand-corrected, algorithm technique.[2,3] Thickness maps for each category were averaged and also subtracted from the average thickness values of the controls to obtain difference maps.
1. On the average difference maps, RGC+ and RNF layer thinning was seen even in the patient groups with MDs better than -1.5 dB and with hemifields classified as normal. 2. The pattern of the thinning was the same for the normal (N), paracentral (P), partial arcuate (pA), and arcuate (A) categories, as well as the MD groups. However, the degree and extent of thinning increased from group N to PC to PA to A, and as MD decreased. 3. On z-score maps, macular RGC+ thinning was about as severe as optic disc RNFL changes. 4. This RGC+ thinning was largely within the central 4 points of the 24-2 field. 5. There was greater thinning in the lower retina.
First, because visual field categories appear to represent different degrees of the same pattern of RGC+ and RNFL damage, a combined VF and OCT map is suggested as an alternative to standard field classification. Second, on average, there is RGC+ damage in the central macula even in patients with normal appearing fields. This damage can be missed on 24-2 tests. Third, the distribution of peripapillary RNFL thickness in controls suggests one possible basis for the clinical finding that glaucomatous defects are more severe and more common in the superior field. Finally, these averaged fdOCT data can be used to test models describing the RNFL projections from macular to optic disc. 1. Keltner, et al (2003) AO; 2. Yang et al (2010) Opt Exp. 3. Raza et a (2011) AO; 4. Hood, Raza (2011) Biomed Opt Exp.
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