Topographic analysis of vascular changes in retrograde trans-synaptic degeneration

Area of Science:

• Ophthalmology
• Neuroscience
• Medical Imaging

Background:

• Retrograde trans-synaptic degeneration (RTSD) and non-arteritic anterior ischemic optic neuropathy (NAION) are optic neuropathies with distinct underlying pathologies.
• Optical Coherence Tomography (OCT) and OCT Angiography (OCTA) are advanced imaging techniques for visualizing retinal structure and vasculature.

Purpose of the Study:

• To investigate the vascular signatures of RTSD using OCT and OCTA.
• To compare the vascular changes in RTSD with those observed in NAION.
• To determine if OCT/OCTA can differentiate between secondary degeneration (RTSD) and primary ischemic injury (NAION).

Main Methods:

• A retrospective cohort study involving 24 eyes with RTSD and 12 eyes with NAION.
• Topographical analysis of retinal regions affected by visual field defects, compared to fellow eyes.
• Calculation of structural (pRNFL, mGCIPL) and vascular (pVD, mVD) parameters as affected-to-control ratios.
• Statistical analysis including Spearman correlation and ANCOVA to assess structure-vascular relationships and group differences.

Main Results:

• Both RTSD and NAION groups showed significant structural and vascular reductions.
• NAION eyes exhibited greater reductions in peripapillary retinal nerve fibre layer (pRNFL), peripapillary vessel density (pVD), and macular vessel density (mVD) compared to RTSD.
• The correlation between macular ganglion cell-inner plexiform layer (mGCIPL) and mVD was stronger in NAION than in RTSD.
• The relationship between structural thinning and vascular loss was more pronounced in NAION.

Conclusions:

• RTSD is characterized by relatively modest vascular compromise compared to NAION.
• The vascular changes in RTSD are likely secondary to reduced metabolic demand from neuronal degeneration.
• Quantitative structure-vascular analysis can help distinguish secondary degeneration from primary ischemic optic neuropathy.