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Reliability of optic nerve head topographic measurements with computerized image analysis
L Dandona1, H A Quigley, H D Jampel
1Wilmer Ophthalmological Institute, Johns Hopkins University, School of Medicine, Baltimore.
American Journal of Ophthalmology
|October 15, 1989
Summary
The Humphrey Retinal Analyzer shows reliable optic disk and rim area measurements. Measurement variability was similar between normal and high intraocular pressure groups, and across different imaging sessions.
Area of Science:
- Ophthalmology
- Medical Imaging
- Optometry
Background:
- Accurate measurement of optic disk area and disk rim area is crucial for diagnosing and monitoring glaucoma.
- Computerized image analysis tools, such as the Humphrey Retinal Analyzer, offer potential for objective and reproducible measurements.
Purpose of the Study:
- To evaluate the reliability of optic disk area and disk rim area measurements using the Humphrey Retinal Analyzer.
- To compare measurement variability between normal subjects and those with increased intraocular pressure.
- To assess the influence of image acquisition timing and subject-specific optic nerve head characteristics on measurement reliability.
Main Methods:
- Ten normal subjects and ten subjects with increased intraocular pressure underwent repeat fundus imaging using the Humphrey Retinal Analyzer.
- Optic disk area and disk rim area were measured from ten images per eye for each subject.
- Variability was assessed between images acquired during the same session and different sessions, and between subject groups.
Main Results:
- No significant difference in variability of optic disk and rim areas was found between normal and high intraocular pressure groups (P > .05).
- Measurement variability was comparable between same-session and different-session images (P > .05).
- Variability was significantly influenced by optic nerve head characteristics, specifically disk edge distinctness and cup wall slope (P < .01).
- Operator input was a significant contributor to overall measurement variability.
Conclusions:
- The Humphrey Retinal Analyzer demonstrates reliable optic disk and disk rim area measurements, comparable to other automated systems.
- Measurement reliability is not significantly affected by intraocular pressure status or imaging session timing.
- Optic nerve head morphology significantly impacts measurement variability, highlighting the need for careful image selection and interpretation.
- Minimizing operator input is essential for enhancing the precision of these measurements in clinical practice.