Comparison of ranked segment analysis (RSA) and cup to disc ratio in computer-assisted optic disc evaluation.

Area of Science:

• Ophthalmology
• Medical Imaging
• Glaucoma Diagnostics

Background:

• Optic nerve head topography is crucial for diagnosing glaucoma.
• The Heidelberg Retina Tomograph (HRT) is a key tool for optic nerve head imaging.
• New analytical methods are continuously being developed to improve diagnostic accuracy.

Purpose of the Study:

• To evaluate the diagnostic precision of ranked segment analysis (RSA) for optic nerve head topography.
• To compare the performance of RSA with traditional vertical cup/disc ratio (vCDR) measurements.
• To assess the clinical utility of RSA in a large sample of normal and glaucomatous eyes.

Main Methods:

• Optic disc images from 153 normal and 75 glaucomatous eyes were analyzed using the Heidelberg Retina Tomograph (software version 2.01).
• Ranked segment analyses and vertical cup/disc ratio measurements were performed on each image.
• Receiver Operating Characteristic (ROC) curves were generated to compare diagnostic performance.

Main Results:

• At 95% specificity, ranked segment analysis sensitivity was 70%, significantly lower than the 85% sensitivity of vertical cup/disc ratio measurements.
• Approximately 30% of glaucomatous discs were misclassified as normal by ranked segment analysis.
• Vertical cup/disc ratio measurements were not corrected for disc size, potentially affecting comparisons.

Conclusions:

• Ranked segment analysis demonstrated unacceptably poor discrimination for glaucoma detection, underperforming compared to the vertical cup/disc ratio.
• The ranking procedure in RSA may lead to the loss of critical spatial information, contributing to its low sensitivity.
• The findings raise significant concerns about the clinical usefulness of ranked segment analysis in glaucoma diagnosis.