A proper diagnosis of glaucoma in a patient must include detection of glaucomatous structural change in the optic disc and retinal nerve fiber layer (RNFL); however, these changes aren’t always clearly visible, especially in myopic eyes. Multicolor imaging may be your best bet in accurately observing RNFL defects; advantages of the modality include sharper images even through small pupils and media opacity and usefulness in the detection of nonglaucomatous or glaucomatous RNFL defects in retinal diseases, as proven by several studies. A new study reviewing the performance of multicolor imaging on myopic eyes found that the modality can effectively visualize glaucomatous RNFL defects that are indistinguishable on more conventional photography, such as fundus or red-free RNFL.
There were 150 eyes from 138 myopic patients included in the study: each had an axial length between 24.2 and 30.7mm, and 41.3% of the eyes were highly myopic. The subjects underwent multicolor imaging using spectral domain optical coherence tomography (SD-OCT), a noninvasive retinal imaging modality that captures images using lasers of various wavelengths. The RNFL visibility score and location of the RNFL defect were both determined for each image by independent observers. RNFL visibility score was graded on a four-point system.
Overall, multicolor imaging was able to visually capture the RNFL defect much more clearly than fundus or red-free RNFL photography and attained a higher RNFL visibility score. Even for highly myopic eyes, visibility scores were also much higher than for fundus or RNFL photography (green-reflectance: 2.8, blue-reflectance: 2.8, multicolor: 2.3, fundus: 2.1, RNFL: 2.2). As for the diagnostic performance of multicolor imaging for detection of superotemporal or inferotemporal RNFL defects, green-reflectance, blue-reflectance and multicolor images had higher sensitivities (94.9%, 93.2%, 91.5%, respectively) than fundus or RNFL photography.
“For detection of inferotemporal RNFL defect, the multicolor imaging showed significantly higher sensitivities than those of the fundus or RNFL photography,” the researchers wrote. “With regard to specificity, the multicolor images showed significantly better performance than that of fundus or RNFL photographs (93.0% vs 84.9 or 84.3%) for detection of superotemporal RNFL defect, and so did blue-reflectance images for detection of inferotemporal RNFL defect (94.9% vs 86.8% or 85.7%).”
“Based on our results, multicolor imaging, which is available on the combined scanning laser ophthalmoscope and SD-OCT platform, enables a dual role for fundus and red-free RNFL photography in a single device: the multicolor image is more likely to take the role of fundus photography, while the blue- and green-reflectance images take the role of red-free RNFL photography,” the authors conclude.
Multicolor imaging may be an excellent tool to distinguish abnormal patterns of axonal fiber bundles in myopic glaucoma patients, excelling over traditional methods. Blue- and green-reflectance images, in particular, may offer the highest level of RNFL visibility to improve diagnostic accuracy.
Kim YH, Ahn J, Kim KE. Multicolor imaging for detection of retinal nerve fiber layer defect in myopic eyes with glaucoma. Am J of Ophthalmol. July 15, 2021. Epub ahead of print.