In Vivo Confocal Microscopy Analysis of Corneal Microstructural Changes in Neurosurgically-Induced Neurotrophic Keratitis

Dong Hyun Lee; Eun Young Choi; Eung Kweon Kim; Hyung Keun Lee

doi:10.3341/jkos.2014.55.12.1765

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Lee, Choi, Kim, and Lee: In Vivo Confocal Microscopy Analysis of Corneal Microstructural Changes in Neurosurgically-Induced Neurotrophic Keratitis

Original Article

J Korean Ophthalmol Soc 2014;55(12):1765-1771.

Published online: 2 September 2014

DOI: https://doi.org/10.3341/jkos.2014.55.12.1765

In Vivo Confocal Microscopy Analysis of Corneal Microstructural Changes in Neurosurgically-Induced Neurotrophic Keratitis

Dong Hyun Lee, MD^1,^*, Eun Young Choi, MD^1,^*, Eung Kweon Kim, MD, PhD^1,², Hyung Keun Lee, MD, PhD^1,^2,

¹Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea

²Institute of Corneal Dystrophy Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea

Address reprint requests to Hyung Keun Lee, MD, PhD, Department of Ophthalmology, Gangnam Severance Hospital, #211 Eonju-ro, Gangnam-gu, Seoul 135-720, Korea, Tel: 82-2-2019-3440, Fax: 82-2-3463-1049, E-mail: shadik@yuhs.ac

^* Dong Hyun Lee and Eun Young Choi contributed equally to the study and manuscript as the first authors.

Received 25 January 2014 Revised 28 March 2014 Accepted 5 November 2014

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

To investigate the changes of the corneal microstructure of neurosurgically-induced neurotrophic keratitis patients compared to normal human corneas using in vivo confocal microscope (IVCM).

Methods

Ten eyes in the normal control group and 11 eyes in the neurosurgically-induced neurotrophic keratitis patient group were included in the present study. After corneal sensitivity tests were performed, thickness of each layer and number of endothelial cells and stromal keratocytes in the cornea were assessed using IVCM. Morphological characteristics of the corneal nerves were measured by ImageJ software.

Results

After analysis of corneal thickness layer by layer, the Bowman's layer was significantly reduced in the neurosurgically-induced neurotrophic keratitis patient group compared with the normal control group (p = 0.016) and the portion of Bowman's layer was significantly reduced in the neurosurgically-induced neurotrophic keratitis patient group compared with the control group (p = 0.024). The nerve fiber length per square-millimeter became significantly shorter compared to the normal control group (p = 0.042). The nerve fiber length per square millimeter showed significant correlations with the number of fibers, number of beading, branching patterns, and nerve tortuosity (p = 0.002, 0.002, 0.013 and 0.034, respectively). The number of endothelial cells and stromal keratocytes, the number of nerve fibers and beading, and the pattern of branching and nerve tortuosity showed no significant differences between the normal and neurosurgically-induced neurotrophic keratitis patient groups.

Conclusions

Our results showed that decreased thickness of Bowman's layer may be related to the decreased corneal nerve distribution, secondary to the dysfunction of trigeminal nerve branch innervating the cornea. The microstructural changes of Bowman's layer can help diagnose the disease and evaluate the current status in neurosurgically-induced neurotrophic keratitis patients.

Keywords: Confocal microscopy, Corneal nerve, Corneal thickness, Neurosurgery, Neurosurgically-induced neurotrophic keratitis

References

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Figure 1.

In vivo confocal microscopy images of normal control cornea acquired from Confoscan 4.0. (A) E ndothelium (B) posterior stroma (C) anterior stroma (D) Bowman's layer (E) epithelium (frame sizes 768 × 576 pixels).

Figure 2.

Corneal nerve fiber measurement. (A) Corneal nerves in Bowman's layer as recorded by using slit scanning confocal microscope (Confoscan 4) and (B) the same image after measurement of nerve fiber length (μm) by using NeuronJ software.

Table 1.

Baseline characteristics of each group

	Control	Neurosurgically induced NK	p-value
Eyes (n)	10 (10)	11 (11)	−
Age (years)	51.60 ± 19.71	51.73 ± 12.91	0.918
Age range (years)	31.89-71.31	38.82-64.64	−
Sex (M/F)	3/7	1/10	0.426
Duration of NK (months)	−	59.27 ± 63.68	−
Time from neurosurgery (months)	−	86.55 ± 98.27	−
Laterality (OD/OS)	3/7	5/6	0.557
log MAR BCVA	0.14 ± 0.22	0.26 ± 0.66	0.197
IOP (mm Hg)	11.90 ± 2.64	11.82 ± 3.13	0.918

Values are presented as mean ± SD unless otherwise indicated; Using the Mann-Whitney U-test, no significant difference was detected in age, sex and laterality.

NK = neurotrophic keratitis; log MAR = logarithm of the minimum angle of resolution; BCVA = best-corrected visual acuity; IOP = intraocular pressure.

Table 2.

Corneal measurement analysis of each group

	Control	Neurosurgically induced NK	p-value
Corneal sensitivity (cm)	5.83 ± 0.41	2.67 ± 2.78	0.026^*
Corneal thickness (μm)
Descemet's membrane & endothelium	36.90 ± 15.60	33.45 ± 13.14	0.589^†
Stroma	408.70 ± 43.77	388.27 ± 110.08	0.579^†
Bowman's layer	20.10 ± 12.90	8.64 ± 6.25	0.016^†
Epithelium	56.70 ± 24.39	49.18 ± 22.42	0.471^†
Total	522.40 ± 71.05	479.55 ± 122.79	0.347^†
Portion of cornea (%)
Descemet's membrane & endothelium	6.90 ± 2.52	7.43 ± 3.48	0.697^†
Stroma	78.67 ± 5.54	80.45 ± 6.88	0.523^†
Bowman's layer	3.79 ± 2.37	1.83 ± 1.14	0.024^†
Epithelium	10.64 ± 3.74	10.29 ± 4.05	0.839^†
Cell count (cells/mm²)
Endothelium	2834.40 ± 265.54	2636.18 ± 545.97	0.311^†
Stroma
Posterior keratocyte	462.42 ± 115.51	450.01 ± 94.19	0.790^†
Anterior keratocyte	517.22 ± 145.57	532.83 ± 201.29	0.842^†
Nerve analysis
Nerve fiber length (μm/mm²)	8677.10 ± 5090.98	4756.59 ± 1640.91	0.042^†
Number of fibers	5.00 ± 2.11	4.00 ± 2.29	0.336^†
Number of beadings	2.20 ± 2.39	1.00 ± 1.00	0.172^†
Branching pattern	1.10 ± 1.10	0.78 ± 0.67	0.457^†
Nerve tortuosity	1.40 ± 1.08	1.00 ± 0.87	0.388^†

Values are presented as mean ± SD; Using the Mann-Whitney U-test, corneal sensitivity demonstrated significant differences between control and neurosurgically induced neurotrophic keratitis group; Using the independent samples t-test, the thickness and portion of Bowman's layer, total nerve fiber length demonstrated significant differences between control and neurosurgically induced neurotrophic keratitis group.

NK = neurotrophic keratitis.

^* Mann-Whitney U-test;

^† Independent samples t-test.

Table 3.

Spearman Rho Correlation for nerve fiber length, number of fibers, number of beading, branching pattern, nerve tortuosity, and corneal sensitivity

		Corneal sensitivity	Number of fibers	Number of beading	Branching pattern	Nerve tortuosity
Nerve fiber length (μm/mm²)	Correlation coefficient	0.268	0.671	0.663	0.559	0.489
	p-value	0.354	0.002^*	0.002^*	0.013^*	0.034^*

Using the Spearman Rho Correlation Analysis, nerve fiber length showed significant correlations with number of fibers, number of beading, branching pattern and nerve tortuosity.

^* p < 0.05.

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