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Normative Variability in Retinal Nerve Fiber Layer Thickness: Does It Matter Where the Peaks Are?
Sowjanya Gowrisankaran1, Ashkan Abbasi1, Xubo Song2
1Department of Ophthalmology, Casey Eye Institute, Oregon Health & Science University, Portland, OR, USA.
Translational Vision Science & Technology
|May 12, 2025
Summary
Peak normalization (PN) of retinal nerve fiber layer thickness (RNFLT) reduces normative variability, improving glaucoma detection. This method enhances the sensitivity and specificity of RNFLT measurements for identifying abnormalities.
Area of Science:
- Ophthalmology
- Medical Imaging
- Biomarker Analysis
Background:
- Retinal nerve fiber layer thickness (RNFLT) is a key biomarker for glaucoma detection.
- Wide normative ranges in RNFLT measurements, due to interindividual variability in peak location, can reduce diagnostic sensitivity and specificity.
- The impact of RNFLT peak location variability on normative ranges has not been fully elucidated.
Purpose of the Study:
- To evaluate the effect of RNFLT peak normalization (PN) on reducing normative variability.
- To assess how PN impacts the accuracy of abnormality detection in glaucoma suspects.
Main Methods:
- Circumpapillary RNFLT profiles were analyzed from optical coherence tomography (OCT) scans of 83 healthy individuals.
- RNFLT peak locations were aligned to average positions, with and without accounting for the fovea-optic nerve head axis.
- Normative ranges were calculated before and after peak normalization.
Main Results:
- Peak normalization (PN) of RNFLT led to a statistically significant overall decrease in the coefficient of variation (CoV) of the normative range by 4.2% (P=0.02).
- Specific clock-hours demonstrated substantial CoV reductions exceeding 10% after PN, particularly in the supratemporal and infratemporal regions.
- PN improved the categorization of abnormalities in RNFLT profiles, correcting for issues caused by peak misalignment.
Conclusions:
- RNFLT peak normalization effectively reduces normative variability, especially in critical supratemporal and infratemporal sectors.
- This normalization technique enhances sectoral abnormality categorization, potentially improving the sensitivity and specificity of RNFLT for glaucoma diagnosis.
