Lamina cribrosa microarchitecture in normal monkey eyes part 1: methods and initial results

Area of Science:

• Ophthalmology
• Neuroscience
• Biomedical Engineering

Background:

• The lamina cribrosa (LC) is a critical structure within the optic nerve head (ONH).
• Understanding its microarchitecture is essential for diagnosing and managing optic neuropathies.
• Previous studies have lacked quantitative microstructural analysis of the LC.

Purpose of the Study:

• To introduce a quantitative method for assessing postmortem lamina cribrosa microarchitecture (LMA).
• To characterize beam diameter (BD), pore diameter (PD), and connective tissue volume fraction (CTVF) in normal monkey eyes.
• To analyze variations in LMA across different sectors and depths of the LC.

Main Methods:

• Digital 3D reconstruction and segmentation of optic nerve heads (ONHs) from 21 normal monkey eyes.
• Calculation of mean BD, PD, and CTVF within defined sectors and depths.
• Statistical analysis using analysis of variance (ANOVA) with general estimating equations to assess sector, subsector, and depth effects.
• Mapping of eye-specific LMA discordance based on connective tissue density.

Main Results:

• Significant sector, subsector, and depth effects were observed for BD, PD, and CTVF (P < 0.01).
• Smaller BD and CTVF, and larger PD were found in the superior-temporal (ST) and inferior-temporal (IT) sectors, particularly in central regions.
• Larger BD and CTVF, and smaller PD were noted in the middle LC layer.
• LMA discordance predominantly occurred in ST and IT sectors, varying by eye, and generally decreased with increasing CTVF.

Conclusions:

• The study quantitatively confirms reduced connective tissue density in the ST and IT ONH regions.
• Significant regional and depth-dependent variations in LC microarchitecture exist.
• The clinical relevance of eye-specific LMA discordance requires further investigation.