Revealing Henle's fiber layer using spectral domain optical coherence tomography

Area of Science:

• Ophthalmology
• Medical Imaging
• Retinal Imaging

Background:

• Spectral domain optical coherence tomography (SD-OCT) is crucial for visualizing retinal structures.
• Traditionally, SD-OCT struggles to delineate Henle's fiber layer (HFL), composed of photoreceptor cell axons.
• Accurate measurement of retinal layers, like the outer nuclear layer (ONL), is vital for clinical research.

Purpose of the Study:

• To present a novel SD-OCT imaging method for reliably identifying Henle's fiber layer (HFL).
• To improve the accuracy of outer nuclear layer (ONL) thickness measurements in retinal imaging.
• To enhance the understanding of retinal layer reflectivity and its association with macular pathology.

Main Methods:

• Prospective imaging of 15 eyes from 11 subjects with normal vision using commercial SD-OCT systems.
• Systematic variation of the SD-OCT beam entry position through the pupil (horizontally and vertically).
• Measurement of outer retinal layer reflectivity and thickness as a function of beam position.

Main Results:

• Henle's fiber layer (HFL) reflectivity showed directional dependence and increased with eccentricity.
• Including HFL in measurements increased the measured outer nuclear layer (ONL) thickness by an average of 52%.
• Four cases demonstrated how macular pathology alters HFL intensity, impacting imaging interpretation.

Conclusions:

• A novel SD-OCT method successfully distinguishes Henle's fiber layer (HFL) from the outer nuclear layer (ONL).
• Accurate ONL thickness measurement is critical for clinical studies utilizing SD-OCT.
• Understanding HFL optical properties aids in interpreting reflectivity changes associated with macular diseases.