Impact of corneal parameters, refractive error and age on density and morphology of the subbasal nerve plexus fibers in healthy adults

Abstract

The purpose of this study was to analyze corneal sub-basal nerve plexus (SBNP) density and morphology and their relationships with corneal parameters and refractive status. In this single center study, in vivo confocal microscopy (IVCM) was performed in 76 eyes of 38 healthy subjects aged 19–87 (mean age 34.987 ± 1.148). Nerve fiber analysis was performed using Confoscan 4 microscope with semi-automated software (Nidek Technologies, Italy) The nerve fiber length (NFL) µm/mm2, nerve fiber density (NFD) no./mm2, tortuosity coefficient (TC), and nerve beadings density (NBD) no./mm were considered. Relationship between SBNP parameters and corneal curvature, thickness, diameter, and refraction were analyzed. Additionally, the association with gender, laterality and age were determined. NFL was inversely correlated with age (r = − 0.528, p < 0.001), myopic refractive error (spherical value) (r = − 0.423, p < 0.001), and cylindrical power (r = − 0.340, p = 0.003). NFD was inversely correlated with age (r = − 0.420, p < 0.001) and myopic refractive error (r = − 0.341, p = 0.003). NBD showed a low inverse correlation with cylindrical power (r = − 0.287, p = 0.012) and a slight positive correlation with K (r = 0.230, p = 0.047). TC showed a significant negative correlation between age (r = − 0.500, p < 0.001) and myopic refractive error (r = − 0.351, p = 0.002). Additionally, there were strong positive correlations between NFL and NFD (r = 0.523, p < 0.001), NFL and TI (r = 0.603, p < 0.001), and NFD and TC (r = 0.758, p < 0.001). Multiple regression analysis revealed age to be the most significant factor affecting SBNP density (B = − 0.467, p = 0.013) and length (B = − 61.446, p < 0.001); myopic refractive error reduced both SBNP density (B = − 2.119, p = 0.011) and length (B = − 158.433, p = 0.016), while gender and laterality had no significant effects (p > 0.005). SBNP fiber length decreases with age, myopic refractive error and cylindrical power. SBNP fiber density reduces with age and myopic refractive error. Corneal nerve parameters are not influenced by gender or laterality.

Characteristics of Corneal Subbasal Nerves in Different Age Groups: An in vivo Confocal Microscopic Analysis

“…19,20 On the other hand, some researchers revealed a correlation between corneal nerve density loss and age. [19][20][21] Therefore, we anticipated that the results of this study, which we intentionally screened from absolutely healthy subjects, limited the age range of participants and compared with those of age matched controls, can be generally applied as a standard baseline characteristic of corneal subbasal nerves to distinguish otherwise invisible abnormalities or degenerative nerve changes from normal nerve findings at each age. In turn, this may support the diagnosis and/or prognostication of some subclinical NK-related conditions and expedite the management of particular ocular and systemic diseases.…”

“…17,18,42,53,54 However, some investigators have revealed contradictory results as they identified that significant nerve loss was related to increasing age. [19][20][21]23,55,56 These studies included subjects older than the age of 60, which was beyond the range of our study group. The rationale that we recruited subjects under 60 years old was to analyze the normal nerve characteristics and to preclude the results of nerve analysis affected from degenerative changes in the elderly.…”

Corneal confocal microscopic characteristics of acute angle-closure crisis

“…Confocal microscopy might be superior to specular microscopy to analyze the endothelial cells in AACC with corneal edema. The confocal microscope can directly obtain images of tissues and cells in each layer of the cornea through continuous confocal scanning, detecting various elements of normal and affected corneas in multiple layers and in vivo, without fixation and staining of tissue sections [9][10][11][12][13][14]. Thus, it is a major method for exploring the pathological mechanism of ophthalmic diseases at the cellular level.…”

“…Confocal microscopy is a novel non-invasive corneal imaging examination method [9][10][11]. Due to high resolution and magnification, it reveals the corneal changes at the cellular level under three-dimensional space and real-time conditions; similar results could be obtained in the cloudy corneal tissue, making it a commonly used tool for the clinical study of corneal lesions [9][10][11][12][13][14].…”

“…Confocal microscopy plays a major role in evaluating keratitis and corneal nerves [9][10][11][12][13][14], but there is only one study about its use for AACC which focused on Langerhans cells and keratocytes [15]. Our study aimed to investigate corneal epithelial cells, subepithelial nerve fiber plexus, stromal cells, and endothelial cells of the AACC and fellow eyes and healthy controls using confocal microscopy.…”