Changes in peripapillary retinal nerve fiber layer distribution by axial length

Area of Science:

• Ophthalmology
• Medical Imaging
• Biometry

Background:

• Peripapillary retinal nerve fiber layer (RNFL) thickness is a key indicator in diagnosing glaucoma.
• Optical coherence tomography (OCT) is widely used for RNFL analysis, relying on normative databases for interpretation.
• Axial length, a measure of eye size, is known to influence various ocular parameters.

Purpose of the Study:

• To evaluate how axial length affects the distribution of peripapillary RNFL thickness.
• To assess the risk of misclassifying healthy individuals as abnormal due to axial length variations when using OCT normative data.

Main Methods:

• Healthy volunteers underwent spectral-domain OCT for RNFL thickness analysis, autorefraction, and axial length measurement.
• RNFL thickness was analyzed across the whole circle, quadrants, and clock hours.
• Linear and logistic regression models were used to determine the relationship between axial length and RNFL parameters, comparing results against a normative database.

Main Results:

• A negative correlation was found between axial length and average 360° RNFL thickness (r = -0.244, p < 0.001).
• Increasing axial length led to decreased RNFL thickness in specific sectors (1, 2, 4, 5, 6, 12 o'clock) and increased thickness in others (7, 8, 9, 10, 11 o'clock).
• Longer axial lengths shifted RNFL hump locations temporally and increased the likelihood of sectors falling below normative limits (p < 0.05).

Conclusions:

• Peripapillary RNFL thickness distribution varies with axial length.
• Axial length is a critical factor that can lead to misleading OCT findings.
• Normative databases for OCT RNFL thickness should incorporate axial length to improve diagnostic accuracy.