Ferreting out the faults
A number of these faults can play tricks on the eyes.
Blood vessel shadows are the products of vessels containing flowing blood. Mirror images or inverted images can result from the position in the scan window at which the image was acquired. Blinking artifacts, which appear as black bands across an image, indicate that the signal was interrupted during a blink or a segmentation error occurred, and eye movement artifacts can distort the shapes of the tissues in an image, Dr. Schuman explained.
Measuring the retinal nerve fiber layer (RNFL)
The health of this structure is assessed in a circular area centered on the optic nerve head. This area of measurement can be used on any of the previously mentioned instruments to obtain a robust assessment of the RNFL.
A volumetric measurement that includes the tissue beyond the old fashioned scan circle is best to determine the development of glaucoma as well as the shape and character of the abnormality, he said. When viewing output from the devices, abnormalities have a particular location and shape.
“This provides the clinician with confidence regarding whether an abnormality is indeed glaucoma,” Dr. Schuman explained. “If the abnormality is located in a place where glaucoma generally develops along with a pattern typically seen in glaucoma, there is a high likelihood that the abnormality is glaucomatous.”