A comparison of structural measurements using 2 Stratus optical coherence tomography instruments

Area of Science:

• Ophthalmology
• Medical Imaging
• Glaucoma Research

Background:

• Accurate measurement of ocular structures is crucial for diagnosing and monitoring eye diseases like glaucoma.
• Optical coherence tomography (OCT) is a key technology for assessing retinal nerve fiber layer (RNFL) thickness and optic disc topography.
• Variability in measurements between different OCT instruments can affect clinical decision-making.

Purpose of the Study:

• To compare RNFL thickness, optic disc topography, and central foveal thickness measurements between two different Stratus OCT instruments.
• To assess the impact of different OCT instruments on diagnostic parameters in normal and glaucoma subjects.

Main Methods:

• Ten normal and ten glaucoma subjects were enrolled.
• Consecutive scans were performed using two Stratus OCT instruments by two operators using standardized protocols (fast RNFL, fast macular thickness, fast optic disc).
• Statistical analyses included two-factor fixed effects ANOVA and variance component analysis to determine variability due to subject, operator, and machine.

Main Results:

• Significant differences (P<=0.003) were found between OCT instruments for average, superior, and inferior RNFL thickness and central foveal thickness in normal eyes.
• In glaucomatous eyes, significant differences were observed in average and superior RNFL thickness and cup/disc area ratio.
• Intermachine variability (0.0%–16.4%) was consistently larger than interoperator variability (0.0%–2.4%) across all measurements.

Conclusions:

• Measurements of RNFL thickness, optic disc topography, and central foveal thickness are not interchangeable between different Stratus OCT instruments.
• The choice of OCT instrument can introduce significant variability, potentially impacting the longitudinal assessment of glaucoma progression.
• Clinicians should be aware of inter-instrument differences when interpreting OCT data for patient management.