Number of macula optical coherence tomography scans needed to detect glaucoma progression.

Background

To evaluate the impact of testing frequency on the time required to detect statistically significant glaucoma progression for ganglion cell complex (GCC) with optical coherence tomography (OCT).

Materials and methods

From multicentre glaucoma registries, 332 eyes of 201 glaucoma patients were enrolled over an average of 4.4 years. Patients with 4 or more OCT tests were selected to calculate the longitudinal rates of GCC thickness change over time by linear regression. A computer simulation was then used to generate real-world GCC data and assess the time required to detect progression at different loss rates and testing frequencies based on variability estimates. Time and accuracy to detect worsening of progression were calculated.

Results

As testing frequency increased, the time required to detect a statistically significant negative GCC slope decreased, but not proportionally. All eyes with a GCC loss of -1 µm/year progressed after 3.8, 2.6 and 2.2 years on average when testing was conducted one, two and three times per year, respectively. For eyes with a GCC loss of -1.5 µm/year, progression was identified after 3.3, 2.2, and 1.8 years on average, respectively.

Conclusion

Increasing the frequency of macular OCT testing to three times per year more sensitively detects progression compared with two times per year. However, two times per year testing may be sufficient in clinical settings to detect progression and also to reduce the healthcare burden.

Trial registration numbers: NCT00221897, NCT00221923.