Increasing OCT Scans May Improve Accuracy for Detecting Glaucoma Worsening

More optical coherence tomography (OCT) scans must be taken to accurately diagnose the deterioration of the retinal nerve fiber layer (RNFL) in patients with glaucoma, according to research published in Ophthalmology.

Clinicians often measure glaucoma worsening by using OCT to assess RNFL thinning.  However, evidence-based studies have not confirmed how accurate these analyses are or how testing strategy impacts accuracy. In this study, researchers used simulations to estimate how accurately OCT can diagnose moderate (75^th percentile) and rapid (90^th percentile) RNFL thinning.

The team included 7392 t patients with glaucoma and glaucoma suspects (eyes, 12,150; 61% women; mean [SD] age, 67.7 [14.8] years) who had 5 or more RNFL thickness measurements with a signal strength (SS) of at least 6 in the analysis. Participants underwent OCT imaging with a mean [SD] interval of 390 [186] days between scans.

According to the report, the median rate of RNFL worsening was −0.39 μm per year. Those with moderate and rapid RNFL thinning experienced thinning at rates of −1.09 μm per year and −2.35 μm per year, respectively. Stratified by quadrant, superior (−0.61 μm/yr) and inferior (−0.74 μm/yr) quadrants experienced more rapid median thinning rates compared with the temporal (−0.18 μm/yr) and nasal (−0.09 μm/yr) sectors. 

Simulations indicate that the mean measurement frequency of the sample (3 OCT scans over 2 years) accurately detected moderate RNFL thinning 47% of the time and rapid RNFL thinning 40% of the time. Accuracy rates for detecting worsening were highest in the inferior quadrant and lowest in the nasal quadrant.

The investigators suggest obtaining 7 OCT scans over 2 years with a clustered measurement strategy to achieve at least 60% accuracy. 

“In summary, we recommend obtaining a much larger number of OCT scans than is currently the norm to accurately detect glaucoma worsening,” the report states. “When practical, a clustered measurement strategy should be used with multiple scans per visit. As OCT is a relatively quick and patient friendly test, we believe providers can easily increase the number of tests per visit to more accurately identify glaucoma worsening.”

Study limitations include the use of only 1 OCT device.