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. 2023 Dec 1;12(12):3.
doi: 10.1167/tvst.12.12.3.

Fully Automatic, Semiautomatic, and Manual Corneal Nerve Fiber Analysis in Patients With Sarcoidosis

Lisette R M Raasing  1 , Oscar J M Vogels  2 , Mirjam Datema  3 , Martijn R Tannemaat  4 , Marcel Veltkamp  1   5 , Jan C Grutters  1   5
Affiliations

Fully Automatic, Semiautomatic, and Manual Corneal Nerve Fiber Analysis in Patients With Sarcoidosis

Lisette R M Raasing et al. Transl Vis Sci Technol. .

Abstract

Purpose: No guidelines are available on the preferred method for analyzing corneal confocal microscopy (CCM) data. Manual, semiautomatic, and automatic analyzes are all currently in use. The purpose of the present study was threefold. First, we aimed to investigate the different methods for CCM analysis in patients with and without small fiber neuropathy (SFN). Second, to determine the correlation of different methods for measuring corneal nerve fiber length (CNFL) and nerve fiber area (NFA). Finally, we investigated the added value of automatic NFA analysis.

Methods: We included 20 healthy controls and 80 patients with sarcoidosis, 31 with established SFN and 49 without SFN. The CNFL was measured using CCMetrics, ACCMetrics, and NeuronJ. NFA was measured with NFA FIJI and ACCMetrics NFA.

Results: CNFL and NFA could not distinguish sarcoidosis with and without SFN or healthy controls. CCMetrics, NeuronJ, and ACCMetrics CNFL highly correlated. Also, NFA FIJI and ACCMetrics NFA highly correlated. Reproducing a nonlinear formula between CNFL and NFA confirmed the quadratic relation between NFA FIJI and ACCMetrics CNFL. CCMetrics and NeuronJ instead showed a square root relationship and seem to be less comparable owing to differences between automatic and manual techniques.

Conclusions: ACCMetrics can be used for fully automatic analysis of CCM images to optimize efficiency. However, CNFL and NFA do not seem to have a discriminatory value for SFN in sarcoidosis. Further research is needed to determine the added value and normative values of NFA in CCM analysis.

Translational relevance: Our study improves the knowledge about CCM software and pathophysiology of SFN.

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Conflict of interest statement

Disclosure: L.R.M. Raasing, None; O.J.M. Vogels, None; M. Datema, None; M.R. Tannemaat, None; M. Veltkamp, None; J.C. Grutters, None

Figures

Figure 1.
Figure 1.
Schematic presentation of a small nerve fiber in different stages in the epidermis. A healthy nerve has a small diameter. The small nerve swells at an early pathological stage before degenerating and can be recognized as SFN with reduced nerve fiber density. Advanced degeneration results severely reduced intraepidermal nerve fiber density. After degeneration, sprouting results in new nerve structures. The graph below shows a schematic progression of NFA and CNFL during the stages of healthy nerve, nerve swelling and nerve degeneration. NFA can detect nerve swelling in the early stage of SFN by measuring an increasing number of pixels in the nerve structures. CNFL will measure a reduced number of pixels when nerve degeneration appears.
Figure 2.
Figure 2.
Examples of NFL calculations. (A) The original 400 × 400 µm image of a patient with sarcoidosis and SFN symptoms. (B) Manual analysis performed with CCMetrics (CNFL = 25.8 mm/mm2). (C) Semiautomatic analysis with NeuronJ (CNFL = 31.74 mm/mm2). (D) Automatic analysis NFA FIJI (NFA = 19,650 µm2/mm2). (E) Automatic analysis performed with ACCMetrics (CNFL = 20.46 mm/mm2).
Figure 3.
Figure 3.
Inclusion and exclusion process; vitamin B12 levels were decreased in one patient, nerve conduction velocity was decreased in four patients, one patient refused the visit owing to an impractical combination of eye drops during a working day, and one patient was diagnosed with neurosarcoidosis. In all, 117 participants were eligible for inclusion.
Figure 4.
Figure 4.
CNFL and cornea NFA (CNFA) boxplots, 25th to 75th percentiles, whiskers min to max and median lines. Four groups were defined based on established SFN, probable SFN, no SFN and healthy controls (HC). (A) CNFL measured with CCMetrics. (B) CNFL measured with ACCMetrics. (C) CNFL measured with NeuronJ. (D) NFA measured with NFA FIJI. (E) NFA measured with ACCMetrics. CNFL and NFA were unable to distinguish between patients with sarcoidosis with established SFN and without SFN.
Figure 5.
Figure 5.
Bland–Altman plots between (A) CCMetrics and ACCMetrics, (B) CCMetrics and NeuronJ, (C) ACCMetrics and NeuronJ, and (D) ACCMetrics and NFA FIJI.
Figure 6.
Figure 6.
Second-order polynomial regression plot to calculate the relationship between cornea NFA and CNFL. The formula of Brines et al. was compared with the formula calculated with data from this study. (A) CCMetrics and NFA FIJI, described by NFA = −4.66 × 10−4 (CNFL) + 4.1 (CNFL) −1580. (B) ACCMetrics and NFA FIJI, described by NFA = 3.94 × 10−4 (CNFL) + 5.57 × 10−1 (CNFL) + 2041. (C) NeuronJ and NFA FIJI, described by NFA = −1.33 × 10−4 (CNFL) + 2.68(CNFL) −1123.
See this image and copyright information in PMC

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