Morphometric Stability of the Corneal Sub-basal Nerve Plexus in Healthy Individuals: A 3-year Longitudinal Study Using Corneal Confocal Microscopy

Abstract

Purpose: To examine the age-dependent alterations and the longitudinal course of sub-basal nerve plexus (SNP) morphology in healthy individuals.

Methods: Sixty-four healthy participants had ocular screening, health and metabolic assessment as well as laser-scanning corneal confocal microscopy examination at baseline and at 12-month intervals for three years. At each annual visit, eight central corneal images of the SNP were randomly selected and analysed using a fully-automated analysis system to quantify corneal nerve fibre length (CNFL). Two linear mixed model approaches were fitted to examine the relationship between age and CNFL and the longitudinal changes of CNFL over three years.

Results: At baseline, mean age was 51.9 ± 14.7 years (range, 15 to 75). The cohort was gender balanced (χ²=0.56, p=0.45). Age (t=1.60, p=0.12) and CNFL (t=-0.50, p=0.62) did not differ between genders. Fifty-three participants completed the 36-month visit and 49 participants completed all visits. No significant change in CNFL was observed over the 36-month period (F_{(1, 55.0)}=0.69, p=0.41). Age had a significant effect on CNFL (F_{(1, 33.2)}=5.46, p=0.03) with a linear decrease of 0.05 mm/mm² in CNFL per one year increase in age (t=-2.3, p=0.03).

Conclusions: CNFL showed a stable course over a 36-month period in healthy individuals, although there was a slight linear reduction in CNFL with age. The findings of this study have implications for understanding the time-course of the effect of pathology and surgical or therapeutic interventions on the morphology of the SNP or suitability of CNFL as a screening/monitoring marker for peripheral neuropathies.

Keywords: 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • 550 imaging/image analysis: clinical