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Correlation found between visual field, SD-OCT results
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Predicting 24-2 visual field thresholds from spectral-domain optical coherence tomography is feasible, according to a study recently published in Investigative Ophthalmology & Visual Science.
Bogunovic and colleagues reported that visual function may be monitored via SD-OCT structural information, aiding in glaucoma management.
"Spectral domain optical coherence tomography (SD-OCT) allows unprecedented, patient-friendly, three-dimensional spatial resolution of the nerve fiber (NFL), ganglion cell (GCL) and inner plexiform (IPL) retinal layers," the authors wrote. "To date, these localized peripapillary NFL measurements have not correlated well with visual function."
They continued: "We hypothesize that novel quantitative metrics of retinal-ganglion-cell axonal complex (RGC-AC) morphology allow improved prediction of visual function and that thickness of SD-OCT derived layers allows quantification of the amount of glaucomatous damage along the RGC-AC, as we assume that measured visual field thresholds are related to RGC-AC layer thicknesses, forming a proxy for the number of axons or ganglion cells."
As detailed in the study, 122 patients with early, moderate and advanced glaucoma were evaluated.
Researchers utilized the Humphrey Field Analyzer (Carl Zeiss Meditec) for standard automated perimetry measurements and Spectralis (Heidelberg Engineering Inc.) for SD-OCT imaging. They defined a wide-field composite OCT and corresponding layer thicknesses after segmenting the OCT images. Based on the 24-2 Matrix, researchers partitioned the wide field retinal area into 54 sections to evaluate structural properties and determine visual field threshold assessments.
Results showed a correlation between measurements of the retinal ganglion cell layer thickness and nerve fiber layer thickness that were derived from the SD-OCT and visual field assessments for the 54 test locations in patients during all stages of glaucoma.
"Our results show that predicting individual 24-2 visual field thresholds from structural information, as derived from wide-field SD-OCT local NFL and GCL+IPL thicknesses measurements and using the RGC-AC concept, is feasible," the authors concluded. "The results show the potential for the predictive ability of SD-OCT structural information for visual function. Ultimately, it may be feasible to complement and reduce the burden of subjective visual field testing in glaucoma patients with the predicted function derived objectively from OCT structure."
Disclosures: This work was supported by grants from the National Institutes of Health.
Perspective
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Derek MacDonald, OD, FAAO
We have all heard it, time and again: “You’re not going to make me do that test with the flashing lights again, are you?”
Despite tremendous improvements, patients still hate perimetry (and have grown to love optical coherence tomography), but given that glaucoma is a disease with serious functional sequelae, it has remained a necessary evil. Employing objective assessment of the entire retinal ganglion cell/nerve fiber layer complex in patients across the spectrum of disease severity, Bogunovic et al. have taken a very important step toward strengthening the long-sought correlation of structure and function.
When considered in light of complementary work being done by other investigators (Zhang, Raza and Hood; Ganeshrao, McKendrick, Denniss, et al.; Swanson, Malinovsky, Dul, et al.; and others), selectively targeting perimetric stimuli to retinal ganglion cells deemed most at-risk through careful analysis of high-quality OCT scans is becoming a reality. Could a decrease in test time actually accompany an increase in test reliability and repeatability? I am not sure who will cheer louder, the patients or the doctors.
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Invest Ophthalmol Vis Sci. 2014;10.1167/iovs.14-15885.
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