Purpose:
To describe test-retest variability of OCT in RVO patients.
Methods:
Center point and central subfield retinal thickness were measuredby OCT in the first 202 SCORE Study participants twice at screening(V1 and V2: median delay=6 min), and once more 1-3 weeks later(V3: median delay = 11.4d) at randomization. Only patients withall visits were analysed.
Results:
Table 1 (changes between timepoints: D12 = V2 - V1; D23 = V3- V2)Means and variancesare fairly constant at each timepoint, but variability of D23significantly exceeds that of D12 (p < 0.001, permutationtest). The disparity remains significant within and constantacross subgroups based on visual acuity, age, disease duration,sex, and diabetes. The absolute value of D23 exceeds that ofD12 in 73%-85% of participants.Table 2 shows that, while V1-V3are highly correlated over time, D12 and D23 tend to be in oppositedirections.Table 2Two clinicalimplications of the data are:1) A 95% confidence interval fortrue retinal thickness of an individual on a particular dayis ±66 µm (center point) and ±28 µm(central subfield).2) Central retinal thickness can change overa few weeks to be outside the 95% range predicted by the same-dayconfidence interval (28% outside for center point, 49% for centralsubfield).
Conclusions:
Our results suggest that observed short-term OCT change is duetomeasurement error plus natural drift over time. Cliniciansand researchers should consider this when using OCT to guidetreatment decisions and when analyzing OCT data.
Clinical Trial:
www.clinicaltrials.gov NCT00105027
Keywords: clinical (human) or epidemiologic studies: natural history • imaging/image analysis: clinical