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Willliam Sponsel, Nancy Satsangi, Matthew Reilly, Sylvia Groth, Stuart McKinnon, Australian Research Council Centre of Excellence in Vision Science (ACEVS); The Jigsaw Effect: Clinical Evidence for CNS Control of Visual Field Loss in Chronic Glaucoma. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4939.
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© ARVO (1962-2015); The Authors (2016-present)
To statistically assess the tendency for the conservation of the binocular visual field in patients with moderate to severe glaucomatous field loss in both eyes. The goal of this work was to determine whether chronic bilateral visual field degeneration can be explained on a bilaterally independent ocular pathologic basis, or if the mathematical evidence indicates that the CNS must help direct the process in an integrated bilateral manner.
Case control study. Subjects: 47 patients with stabilized chronic progressive glaucoma undergoing Humphrey Visual Field 30-2 testing were evaluated. One single-session paired set of left (OS) and right (OD) eye visual fields was assessed for each individual. Each OS visual field locus was paired with either (a) its directly comitant OD locus, or (b) a random non-comitant OD locus of equal eccentricity from fixation. Mean threshold values were calculated for the 76 loci of each eye of all 47 subjects. The mean value for the higher of each of the paired individual comitant locus values (HCD) from both eyes, using combinations (b) and (c), were similarly calculated for all subjects, using all 76 points OU, running 10,000 iterations for (b), and compared by paired t-test.
Global mean thresholds were 14.73 OS and 15.80 dB OD; mean 15.27 OU, ~5 dB lower than the better of the paired loci (p<0.000000001). Mean threshold for direct HCD pairings (a) was 20.55, versus 20.10 (range 19.9-20.2) for (b) (p=0.0002). Mirrored field pairings confirmed that anatomic symmetry factors could not account for the observed differences.
A very strong tendency for optimizing the binocular visual field, in a manner that defies simple anatomic symmetry considerations, was observed. Direct inspection of the paired visual fields of these patients provides insights into this phenomenon, displaying the interlocking, mutually asymmetric jigsaw-like character of many bilateral scotomata. It is known that focal axonal injury in one eye may be accompanied by increased activity in the contralateral retinal glia and geniculate layers receiving comitant visual information from the fellow non-injured eye (see Bodeutsch et al, J Neurobiol 1999, Penagis et al, Eur J Neurosci 2005, Dai et al, Exp Eye Res 2009). Focal bilateral compensation of this kind may be involved in the conservation of the binocular visual field in patients with chronic progressive glaucoma.
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