_Applied_  
_sciences_  
_Article_  
New Method for the Automated Assessment of Corneal Nerve  
Tortuosity Using Confocal Microscopy Imaging  
**[PERSON] 1,2,3,*(r)**, [PERSON] 1(r), [PERSON] 1,3,4(r), [PERSON] 1,4(r),  
**[PERSON] 1,3(r)** and [PERSON] 1,4(r)  
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Footnote  
the evaluation of the corneal sub-basal nerve plexus [4]. This examination technique was reported to be clinically useful for corneal evaluation during the 1990s [5]. Later, several methods were developed for quantifying corneal IVCM image parameters. [PERSON] and [PERSON] [6] showed that the technique allows for the characterization of the sub-basal corneal plexus using the following parameters, among others: density, length, number, width, tortuosity or even reflectivity of corneal nerves. Subsequently, multiple studies [7; 8; 9] have confirmed that numerous properties of corneal nerves are linked to both ocular and systemic disorders. Thus, IVCM has naturally taken on new importance as the clinical method of choice to analyze corneal nerve structure [10]. The degree of curvature in the nerves of the corneal sub-basal plexus is known as corneal nerve tortuosity. A high-tortuosity nerve is meaningfully curved and has many twists (Figure 1a). In contrast, a low-tortuosity nerve appears approximately straight (Figure 1b). Estimating corneal nerve tortuosity from IVCM images is an important challenge for vision science [7]. Corneal tortuosity analysis could be useful to improve eye disease diagnosis because there is a relevant connection between some ocular and systemic diseases and corneal nerve tortuosity [11; 12]. In particular, several studies have reported a strong positive correlation between corneal nerve tortuosity and dry eye disease (DED) [13; 14; 15; 16; 17]. In addition, it is commonly accepted that the structure and function of the ocular nerves are altered in DED combined with ocular pain [18; 19; 20]. Moreover, sub-basal nerve tortuosity is increased in the short term after corneal refractive surgery [21]. Tortuosity has also been investigated in healthy subjects [22], and in other diseases such as non-neurological autoimmune diseases [23], diabetic neuropathy [7; 12; 24], glaucoma [25], unilateral herpes zoster [26], acute acanthamoeba and fungal keratitis [27] and herpes simplex keratitis [28]. In order to establish a link between tortuosity and ocular or systemic anomalies, the degree of nerve fiber tortuosity has been commonly measured on an ordinal scale [8; 29], which directly implies adding an element of subjectivity in the grading process. Different criteria have been used to define and measure the tortuosity of different anatomical structures such as intracerebral vasculature [30] or retinal vessel [31]. Once the anatomical structure is identified in an image, it will be represented as a group of pixels with a curvilinear shape, and then its tortuosity can be measured. Designed measurements are based on different features such as length [30; 31], angle [32; 33; 34] and curvature [35], but there is no standard measure for quantifying the tortuosity of nerve fibers [36].