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

Chareenun Chirapapaisan,1 Sittiphong Thongsuwan,1 Niphon Chirapapaisan,1 Pratuangsri Chonpimai,1 Anupong Veeraburinon2 1Department of Ophthalmology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand; 2Research Division, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, ThailandaCorrespondence: Niphon ChirapapaisanDepartment of Ophthalmology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, ThailandTel +662 419 8037Fax +662 414 1232Email niphon.chi@mahidol.ac.thPurpose: To determine the normative characteristics of corneal subbasal nerves in different age groups using laser scanning in vivo confocal microscopy (IVCM).Patients and Methods: This descriptive observational study recruited healthy subjects (aged 20– 60 years) from Siriraj Health-Screening Center. Excluded were individuals who had abnormal ocular symptoms, previous ocular surgery, a history of any diseases related to systemic and/or corneal neuropathy, or abnormal corneal sensitivity. Corneal IVCM (HRT3/Rostock Corneal Module) was performed at the central cornea to analyze the subbasal nerve plexus. The corneal nerve characteristics, comprising the number and density of nerves (main nerve trunks, branches, and total nerves) were analyzed using the NeuronJ program, and the corneal nerve tortuosity was graded. The correlations between the subbasal nerve density, tortuosity and age were then analyzed.Results: Eighty subjects were enrolled, with twenty in each of four age groups (20– 30, > 30– 40, > 40– 50, and > 50– 60 years). Overall, the mean number and density of main nerve trunks were 27.93± 0.81/mm2 and 11.22± 0.30 mm/mm2, respectively. As of the nerve branches, the average number and density were 103.56± 2.37/mm2 and 9.15± 0.30 mm/mm2, respectively. The total nerve density was 20.37± 0.39 mm/mm2. There were no significant differences between subbasal nerve parameters of the four age groups. It is noteworthy that 65% of the subjects aged over 40 years revealed high-grade nerve tortuosity.Conclusion: The corneal subbasal nerve numbers and densities were not significantly different among a healthy population aged 20– 60 years. However, there was a trend towards high tortuosity of the corneal nerve in people aged over 40 years.Keywords: in vivo confocal microscopy, IVCM, corneal subbasal nerves, normal characteristics, ag