• Detecting Glaucoma Progression: Trend-Based Analysis or the Rule of 5

    By Jean Shaw
    Selected By: Henry D. Jampel, MD, MHS

    Journal Highlights

    Ophthalmology Glaucoma, November/December 2020

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    To evaluate glaucomatous progression, many clinicians use the “rule of 5” to gauge the rate of change in the retinal nerve fiber layer (RNFL), as seen on spectral-domain optical coherence to­mography (SD-OCT). That is, a loss of 5 μm of global RNFL is considered to be evidence of progression when a fol­low-up scan is compared with baseline scanning results. Thompson et al. com­pared results derived from use of the rule of 5 with the results of trend-based analysis of SD-OCT scans. They found that trend-based analysis outperformed the rule of 5 for identifying progression in glaucomatous eyes.

    For this prospective study, the researchers evaluated 300 eyes of 210 patients. The patients were followed for an average of 5.4 ± 1.5 years and were examined during a median of 11 visits (range, 7-14). All participants complet­ed at least five SD-OCT tests during a two-year period.

    Using trend-based analysis, eyes were considered to have progressed if the slope was negative and statistically significantly different from zero (p < .05). The specificity of trend-based analysis was matched to that of the rule of 5 to allow meaningful comparison of the hit rate (the proportion of glauco­ma eyes categorized as progressing at each time point). The main outcome measure was the comparison between hit rates of trend analysis versus the rule of 5 when results were matched for the same specificity.

    When the two methods were matched, hit rates obtained for the trend-based analysis were greater than those for the rule of 5. By comparing the two meth­ods, the researchers determined that trend-based analysis was able to detect progression in 18.5% to 26.3% more eyes than the rule of 5 during each year of the study.

    The authors acknowledge limita­tions in the study, including their use of global average RNFL rather than sectorial measurements to assess progression. Nonetheless, they said, trend-based analysis was superior to the rule of 5 for identifying progression and should be preferred as a method for longitudinal assessment of global SD-OCT RNFL change over time.

    The original article can be found here.