Abstract
The cornea is one of the regions with the highest density of nerve terminals in the animal body and it bears such functions as nourishing the cornea and maintaining corneal sensation. In veterinary clinical practice, the corneoscleral limbus incision is frequently applied in cataract surgery, peripheral iridectomy, and other procedures for glaucoma. Inevitably, it would cause damage to the nerve roots that enter the cornea from the corneal limbus, thus inducing a series of complications. In this paper, the in vitro cornea (39 corneas from 23 canines, with ages ranging from 8 months old to 3 years old, including 12 male canines and 11 female canines) was divided into 6 zones, and the whole cornea was stained with gold chloride. After staining, corneal nerves formed neural networks at different levels of cornea. There was no significant difference in the number of nerve roots at the corneoscleral limbus between different zones (F = 1.983, p = 0.082), and the nerve roots at the corneoscleral limbus (mean value, 24.43; 95% CI, 23.43–25.42) were evenly distributed. Additionally, there was no significant difference in the number of corneal nerve roots between male and female canines (p = 0.143). There was also no significant difference in the number of corneal nerve roots between adult canines and puppies (p = 0.324). The results of the above analysis will provide a reasonable anatomical basis for selecting the incision location and orientation of penetrating surgery for the canine cornea in veterinary practice.
Highlights
Accepted: 6 December 2021The corneal surface is one of the zones with the highest density of nerve terminals, in which the density of corneal epithelial nerve terminals is 20–40 times that of nerve terminals in the dental pulp and 300–600 times that of cutaneous epithelial nerve terminals [1,2].There are numerous sensory nerves and pain receptors on the corneal surface, which are mainly innervated by the long ciliary nerves derived from the ophthalmic branch of trigeminal nerves
The author believes that aging reduces the number of central epithelial nerve terminals
It is generally believed that canines under 1 year old are puppies and canines from 1 to 7 years old are adults
Summary
There are numerous sensory nerves and pain receptors on the corneal surface, which are mainly innervated by the long ciliary nerves derived from the ophthalmic branch of trigeminal nerves. The primary pain receptors are located in the epithelial layer, while the pressoreceptors are mainly located in the stromal layer [3]. Corneal nerves possess the sensory function, and provide various metabolic nutrition and support for the cornea, including regulating ion transport, the proliferation, differentiation, adhesion, and migration of cells and wound healing. They are significant for maintaining the normal structure and function of the cornea [4].
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