Optic Nerve Head Measurements With Optical Coherence Tomography: A Phantom-Based Study Reveals Differences Among...

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Medical Imaging

Background:

• Optical coherence tomography (OCT) is crucial for glaucoma monitoring by assessing optic nerve head (ONH) dimensions.
• Existing clinical studies highlight variability in retinal dimension measurements between different OCT devices.
• Standardized comparison methods are needed to evaluate OCT device performance for ONH analysis.

Purpose of the Study:

• To develop and utilize ONH morphology mimicking phantoms for inter-device comparison of clinical OCT systems.
• To assess the accuracy and consistency of ONH measurements (cup-to-disc ratio and cup volume) across multiple OCT devices.

Main Methods:

• Fabrication of three ONH phantoms: one normal and two simulating glaucomatous anatomies.
• Scanning of phantoms using Stratus, RTVue, and Cirrus clinical OCT devices, plus a laboratory OCT system as reference.
• Analysis of device-reported ONH measurements and comparison with offline manual and custom software algorithm measurements.

Main Results:

• Significant inter-device differences were observed in 16 out of 18 comparisons of device-reported ONH measurements.
• Mean absolute differences for cup-to-disc ratio (CDR) were 0.082 (device-reported) vs. 0.013 (offline).
• Mean absolute differences for cup volume were 0.044 mm³ (device-reported) vs. 0.019 mm³ (offline), with Cirrus offline measurements differing significantly from Stratus and RTVue.

Conclusions:

• Proprietary ONH analysis algorithms are the primary cause of inter-device measurement variability in OCT devices.
• Applying a consistent offline analysis technique significantly improves measurement similarity across different OCT devices.
• Phantom-based studies offer valuable insights into OCT measurement characteristics for ONH assessment in glaucoma.