AT A GLANCE
• Clinicians need to confirm a few rules of accurate optical coherence tomography imaging before accepting the results: signal strength, motion artifact, and proper acquisition of the image.
• When assessing progression, physicians must determine whether or not changes are clinically significant and, if so, whether they are a result of glaucoma or something else.
Assessing progression presents different challenges. The software must be capable of aligning to the baseline or previous image acquired in terms of location as well as angulation, because a small but different tilt of the head can result in erroneous interpretation. The physician must also determine if the change detected by the machine is clinically significant (greater than 2 standard deviations of the measurement reproducibility2). When reviewing macular measurements, clinicians must consider whether a change is a result of glaucoma, release of the posterior vitreous attachments to the RNFL, or improvement of overall blood sugar control (Figure 2). Moreover, in the presence of uveitis, coexisting RNFL edema and subclinical macular edema can result in erroneous interpretation of normal-appearing thickness.3,4 Upon subsequent resolution of such edema (with uveitis treatment), the thickness of these layers can dramatically decrease once again, giving an erroneous interpretation of glaucomatous progression.
Cystic spaces in the RNFL or subretinal space in the peripapillary region in myopia as well as cystic changes in the outer plexiform layer in rapidly advancing glaucoma can also confound interpretation.4 Masqueraders of glaucoma such as neurosyphilis, optic disc drusen, ischemic optic neuropathy, hemianopia, and optic neuritis present another set of challenges to the assessment of OCT results (Figure 3).5