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Donald Hood, Ali Raza, Ilana Traynis, C. Gustavo De Moraes, Jeffrey Liebmann, Robert Ritch; A Test of a Schematic Model of Glaucomatous Damage of the Macula. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2248.
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© ARVO (1962-2015); The Authors (2016-present)
To test the hypothesis that a recent model [1,2] of glaucomatous damage of the macula, based upon OCT data, predicts the pattern of early defects seen on visual field (VF) tests.
In a prospective study, 10-2 VFs (2° test grid; HFA II, CZM, Inc.) were obtained from 100 consecutive eyes with glaucomatous optic neuropathy and a reliable 24-2 VF with a mean deviation (MD) better than -6 dB. Thus, 24-2 VFs ranged from ‘normal’ to mild defects. At each point of the 10-2 VF, the total deviation (TD) values were averaged across eyes and the number of abnormal points (Ncrit) with TD values below a criterion (crit) level of -5, -10, or -15 dB calculated. The data and model are shown in retinal view in figs. 1 and 2, with the location of the points morphed to account for retinal ganglion cell displacement near the fovea [1-3]. In addition, the average TD values of the two regions of the model were compared.
According to the model (fig. 1), most of the inferior macula (within red border) is relatively more vulnerable to damage because it projects largely to the inferior (I) quadrant of the disc, known to be the most common site of glaucomatous damage. The region within the dark gray border encompasses a small portion of the inferior, and the entire superior, macula. This region is relatively less vulnerable because it projects to the temporal (T) quadrant of the disc, known to be less affected by glaucoma. The pattern of both the average TD (fig. 2A) and the Ncrit (see fig. 2B for criterion of -5dB) values showed good agreement with the model. In addition, the average TD value for the red (vulnerable) region was -4.60 dB, significantly (p<<0.001; paired t-test) less than the value of -1.36 dB for the gray region.
VF losses of macular sensitivity observed in a prospective study of patients with mild glaucomatous damage conform to the pattern predicted by the model. The vulnerable region of the inferior macula (upper VF) is poorly sampled by the most common VF test (the 24-2 with a 6° grid).[1.2] 1. Hood, Raza et al, TVST, 2012; 2. Hood, Raza et al, PRER, 2012; 3. Raza et al, AO, 2011.
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