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SD-OCT imaging valid in identifying localized glaucomatous RNFL damage
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High correlations between spectral domain optical coherence tomography retinal nerve fiber layer maps and photography in RNFL defects were reported in a study recently published in the Journal of Glaucoma.
Shin and colleagues said that the correlation suggests that SD-OCT RNFL imaging is effective in discovering localized glaucomatous RNFL damage.
Researchers conducted a study of 60 eyes with localized RNFL defects to compare imaging. Using SD-OCT (OCT-2000, software version 7.11, Topcon), researchers collected a RNFL thickness map and significance map. Researchers took red-free RNFL photographs with a confocal scanning laser ophthalmoscope (cSLO, F-10, Nidek). They compared angular width, angular location and areas of localized RNFL defects between RNFL photographs and the thickness and significance maps. Additionally, they assessed potential correlations between structural and functional parameters and RNFL defect areas.
Results showed that the RNFL defect area of the RNFL thickness map was significantly smaller than the yellow significance map and the RNFL photograph; it was also significantly greater than the red significance map. Researchers also reported that the angular location, angular width and area of localized RNFL defects in RNFL photographs was strongly correlated with RNFL significance and thickness maps. There was also a significant relationship between structural-functional parameters and the RNFL defect area.
"The high topographic correlations of RNFL defects between cSLO RNFL photography and SD-OCT RNFL maps support the validity of SD-OCT RNFL imaging for detecting localized glaucomatous RNFL damage," the authors concluded. "Combined interpretation of RNFL thickness maps and significance maps provides useful information about glaucomatous RNFL changes in clinical practice.
“In addition, structural and functional parameters are closely related to RNFL defect area, and quantitative measurement of RNFL defects may be valuable for diagnosing glaucoma," they said. – by Chelsea Frajerman Pardes
Disclosure: The authors report no relevant financial disclosures.
Perspective
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Carl H. Jacobsen, OD, FAAO
Retinal nerve fiber layer (RNFL) defects have long been considered a subtle clinical sign of early glaucoma. To detect this important finding, astute clinicians frequently examine patients at low magnification with red-free illumination and acquire red-free photographs.
Shin and colleagues in their recent paper have shown that NFL defects seen on photos correlate well with spectral domain optical coherence tomography (SD-OCT) mapping of the RNFL. They conclude that their findings validate the use of SD-OCT in detecting and managing glaucoma: a reasonable conclusion.
In an era where clinicians are becoming increasingly dependent on expensive technology, this paper’s conclusion might serve as a reminder that conventional tools commonly utilized during the clinical exam may be as sensitive to early glaucoma change as SD-OCT data. In fact, this study found that NFL defect area and angular NFL defect width measured smaller with the OCT than with red-free photos, suggesting that photos may be a more sensitive early indicator of glaucoma change. Of course, once detected, the OCT will give valuable thickness data, which will assist in glaucoma management.
In the final analysis, we need to utilize all available tools in our fight against this subtle but potentially blinding disease.
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