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Study shows combined structure, function tests improve glaucoma detection
In a recent Journal of Glaucoma study, researchers found that the combination of frequency doubling technology and scanning laser polarimetry increased the ability to detect early, moderate and severe glaucoma.
Mwanza and colleagues evaluated 110 normal participants and 114 participants with glaucoma. Researchers used the frequency doubling technology (FDT) C-20-5 screening protocol and scanning laser polarimetry with variable corneal compensation (GDx-VCC).
The devices were tested individually and combined, using GDx-NFI (nerve fiber indicator), GDx-TSNIT (temporal-superior-nasal inferior-temporal), number of missed points of FDT and normal or abnormal FDT, as detailed in the study.
Researchers tested specificity, sensitivity, area under the curve, Akaike's information criterion and prediction confidence interval lengths.
Results showed that combining GDx-TSNIT, number of abnormal points on FDT (NAP-FDT), and the interaction GDx-TSNIT×NAP-FDT detected glaucoma, regardless of severity, with a sensitivity of 94.6% and specificity of 89.5%. In comparison, the best single-variable model (GDx-NFI) detected glaucoma with a sensitivity of 87.8% and specificity of 84.2%.
"Combining FDT C-20-5 protocol and GDx-VCC improves glaucoma detection in comparison with GDx or FDT used alone," the authors concluded. "The combination of GDx-TSNIT, NAP-FDT and their interaction provides the best glaucoma discriminating model."
Disclosure: The authors declare no conflict of interest.
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The reconciliation of structural and functional change in glaucoma has been long sought, yet elusive. Building upon the work of Harwerth and colleagues, Medeiros and colleagues recently developed a combined index of structure and function that estimates the number of surviving retinal ganglion cells by integrating standard automated perimetry and optical coherence tomography analysis of retinal nerve fiber layer thickness (RNFL).
Given the public health burden of undiagnosed glaucoma, a simple yet sensitive and specific means of assessing structure and function would be invaluable. Mwanza and colleagues propose combining the results of GDx RNFL analysis and FDT perimetry, two portable instruments that are easy to administer and comprehend, to fulfill these criteria. Not surprisingly, detection of early and severe disease was driven by RNFL and visual field analysis respectively; however, the multivariable model consistently provided a better combination of sensitivity and specificity than either device used independently.
Supported by rigorous statistical analyses, the authors present compelling data for the use of GDx and FDT as an effective and efficient population screening for glaucoma.
Reference:
Medeiros FA et al. Arch Ophthalmol. 2012;130:1107-1116.
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J Glaucoma. 2014; doi: 10.1097/IJG.0000000000000065.