In order to detect glaucoma progression before significant vision loss occurs, it is important to conduct regular visual field testing. However, little is known on how frequently testing needs to be performed in order to identify glaucomatous progression sooner, thus allowing for earlier intervention and prevention of irreversible vision loss.
Study design
The study employed a computer simulation to determine the optimal frequency of visual field tests for detecting glaucoma progression. The simulation utilized data from 139 patients with glaucoma (277 eyes) from a longitudinal study conducted in the Netherlands. The rate of visual field loss was divided into 3 categories: slow (0 to −0.5 dB/year), moderate (−0.5 to −1.0 dB/year), and fast (−1.0 to −2.0 dB/year). Within each rate category, the study implemented 5 different scenarios to assess the impact of testing frequency on detecting glaucoma progression. The scenarios varied in how frequently the visual field testing occurred, and whether it was regular or irregular; i.e., whether the same testing interval was maintained throughout. Progression was defined as a statistically significant negative mean deviation slope observed in 2 consecutive visits. In cases where progression was detected, simulated eyes underwent repeat testing as a confirmatory measure. If progression was not confirmed, the testing frequency would return to its original scenario.
Outcomes
The simulation demonstrated a higher likelihood of incorrectly detecting progression if no confirmatory test was done when progression was first suspected. The results also indicated that more frequent testing facilitated earlier detection of progression. However, after a 2-year period, similar performance in glaucoma progression detection was observed across different monitoring scenarios, even with fewer tests per year. Notably, eyes with faster progression showed earlier detection compared to eyes with slower progression.
Limitations
One potential limitation of the study is its reliance on computer simulation rather than real-world patient data, which may not fully capture the complexities and variabilities present in actual clinical settings. Moreover, the study's conclusions regarding the optimal frequency of visual field tests may not account for individual patient factors such as overall health status, treatment adherence, or the presence of other eye conditions, all of which can impact glaucoma progression. Additionally, the simulation solely utilized visual field data to detect progression, and did not incorporate optic nerve or retinal nerve fiber layer imaging. Lastly, the study only included patients with baseline mild glaucoma, and therefore the findings cannot be extrapolated to patients with moderate or severe glaucoma.
Clinical significance
This article provides valuable insights into determining the optimal frequency of visual field tests for detecting glaucoma progression. More frequent testing improves the ability to detect progression, particularly in patients with rapid disease progression or higher variability in their visual field measurements. The study suggests that a monitoring routine involving testing every 4 months in the first 2 years, followed by 1 or 2 tests per year depending on the disease status, is the most beneficial. The study also underscores the significance of establishing a reliable baseline through 2 initial visual field tests and confirming progression through a second confirmatory test when progression is first suspected.
Financial disclosures: Dr. Lilian Nguyen discloses no financial relationships.