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Amy Schnegg, William Eric Sponsel, Matthew Aaron Reilly, Ted Maddess; Complementarity of Binocular Nerve Fiber Layer Loss on Optical Coherence Tomography in Bilateral Glaucoma. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4565.
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© ARVO (1962-2015); The Authors (2016-present)
To determine if an anatomical relationship exists in the preservation of visual function in bilateral glaucoma using clinical OCT paired RNFL thickness values.
Paired sets of clinical OCT RNFL thickness data from Optovue's RTVue were taken from 13 patients with bilateral glaucoma ranging from mild to severe FDT visual field loss. Only the superior temporal (ST), superior nasal (SN), inferior temporal (IT) and inferior nasal (IN) sectors were used due to the temporal sector values representing very tight and complex nerve fiber bundles compared to their nasal sector complements. The RNFL thickness data from each sector was normalized against per-sector average healthy RNFL thickness (i.e. ST 140 µm, SN 120 µm, IT 150 µm, IN 140 µm). Complementary sectors (ST OD/SN OS, SN OD/ST OS, IT OD/IN OS, and IN OD/IT OS) were paired and the better of the two determined as binocular RNFL thickness score OU. The four sector values for OD, OS, and OU were averaged to generate a mean RNFL thickness score for each of the 13 patient’s OD, OS and OU. A paired t test of the mean RNFL thickness scores was used to determine the significance of the difference between OD/OS and monocular/binocular score.
Mean (+/- standard error) RNFL thickness for OD, OS, and OU were respectively 86.3+/-18.3 um, 91.1+/-22.3 um, and 98.2+/-20.9 um. RNFL thickness was not significantly different between OD and OS (p=0.38) but OD and OS were both significantly lower than OU (p=0.006 and p=0.004, respectively). Figure 2
The bilateral RNFL thickness score being significantly higher than the monocular scores suggests that the combined anatomical preservation of RNFL thickness does occur in order to preserve visual function in the binocular field. Similarly to a prior oral presentation (Sponsel et al., ARVO 2013 E-abstract 54:4939) of a larger set of clinical data from Carl Zeiss Cirrus OCT RNFL thickness values from patients with severe Humphrey Visual Field loss (Figure 1), our Optovue data set has the similar finding of higher normalized RNFL thickness values binocularly even on a small data set of mild and moderate FDT visual field loss patients. Both OCT data sets having sectors with diffuse RNFL representation even further suggests the significance of binocular anatomical preservation of visual function, if able to study focal paired anatomical complements.
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