Correlation Between Central Corneal Thickness and Retinal Nerve Fiber Layer Thickness in Normal Tension Glaucoma

Je Hyung Hwang; Jae Suk Kim; Joo Hwa Lee

doi:10.3341/jkos.2010.51.1.63

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Hwang, Kim, and Lee: Correlation Between Central Corneal Thickness and Retinal Nerve Fiber Layer Thickness in Normal Tension Glaucoma

Original Article

J Korean Ophthalmol Soc 2010;51(1):63-69.

Published online: 7 September 2010

DOI: https://doi.org/10.3341/jkos.2010.51.1.63

Correlation Between Central Corneal Thickness and Retinal Nerve Fiber Layer Thickness in Normal Tension Glaucoma

Je Hyung Hwang, MD, Jae Suk Kim, MD, Joo Hwa Lee, MD

Department of Ophthalmology, Inje University College of Medicine, Sanggye Paik Hospital, Seoul, Korea

Address reprint requests to Joo Hwa Lee, MD Department of Ophthalmology, Inje University College of Medicine, Sanggye Paik Hospital #761-1 Sanggye 7-dong, Nowon-gu, Seoul 139-707, Korea Tel: 82-2-950-1096, Fax: 82-2-935-6904, E-mail: joohlee@paik.ac.kr

Received 27 April 2009 Accepted 22 September 2009

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 correlation between central corneal thickness (CCT) and peripapillary retinal nerve fiber layer (RNFL) thickness in the eyes of patients with normal tension glaucoma (NTG) at the initial examination and to examine the difference in the degrees of damage of RNFL thickness depending on the CCT.

Methods

Fifty-one eyes of 36 patients with NTG were included in the study, and 51 eyes of 30 people without the disease were used as a control group. CCT and peripapillary RNFL thickness were measured in each eye by ultrasonic pachymetry and optical coherence tomography(OCT), respectively. Patients from the normal NTG group who underwent OCT more than three times inthree years were identically assigned to two groups based on CCT: thin (＜ 553.6 μ m) and thick (≥ 553.6 μ m). Thus, a comparison of the changes in the thickness of retinal nerve fiber layer was performed between the two groups.

Results

Patients with NTG showed a significant positive correlation between CCT and the mean peripapillary RNFL thickness at the initial examination (R=0.68, p<0.01). There were no significant differences in the changes in thickness of RNFL between the groups based on CCT (p>0.05)

Conclusions

At the time of initial diagnosis of NTG, there was a significant correlation between the thickness of CCT and RNFL. Howeverthere was no significant correlation between the thickness of CCT and the progression of the damage of RNFL.

Keywords: Central corneal thickness, Normal tension glaucoma, Optical coherence tomography, Retinal nerve fiber layer

References

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Figure 1.

Correlation between central corneal thickness and average peripapillary retinal nerve fiber layer (RNFL) thicknessin normal group (Pearson correlation coefficient=-0.26, p=0.07).

Figure 2.

Correlation between central corneal thickness and average peripapillary retinal nerve fiber layer (RNFL) thickness in normal tension glaucoma group (Pearson correlation coefficient=0.68, p<0.01).

Table 1.

Comparison of clinical characteristic sand central corneal thickness between normal group and normal tension glaucoma group

	Normal (n=51 eyes)	Normal tension glaucoma (n=51 eyes)	p-value^*
Age (years) (Mean± SD)	52.80±8.70	57.13±9.57	0.069
Spherical Equivalent (diopter) (Mean± SD)	−0.41±2.24	−0.35±1.71	0.882
Intraocular Pressure (mmHg) (Mean± SD)	16.53±2.53	13.88±1.53	<0.05
Central Corneal Thickness (μm) (Mean± SD)	552.86±32.71	543.19±37.24	90.167

^* Statistical significance was tested by paired t-test.

Table 2.

Comparison of peripapillary retinal nerve fiber layer between normal group and normal tension glaucoma group at initial examination

Peripapillary RNFL thickness	Normal (n=51 eyes)	Normal tension glaucoma (n=51 eyes)	p-value^*
Superior (μm)	115.43±18.32	94.14±22.89	<0.001
Inferior (μm)	119.88±20.15	95.04±27.06	<0.001
Nasal (μm)	72.30±6.75	65.67±12.98	<0.001
Temporal (μm)	74.84±13.06	59.90±11.92	<0.001
Average (μm)	95.50±10.38	79.95±16.49	<0.001

^* Statistical significance was tested by paired t-test.

Table 3.

Correlation between central corneal thickness and peripapillary retinal nerve fiber layer thickness in normal group and normal tension glaucoma group

	Normal (n=51 eyes)		Normal tension glaucoma (n=51 eyes)
	R^*	p-value†	R^*	p-value^†
Superior (μm)	−0.23	0.11	0.48	<0.01
Inferior (μm)	0.00	0.98	0.63	<0.01
Nasal (μm)	0.05	0.73	0.44	<0.01
Temporal (μm)	0.13	0.36	0.28	0.04
Average (μm)	−0.26	0.07	0.68	<0.01

^* R=Pearson's correlation coefficient

^† Analysis of variance with Pearson's correlation.

Table 4.

Patients characteristics and corrected intraocular pressure grouped by central corneal thickness

	Group 1 (CCT<553.6 μm)(n=19 eyes)	Group 2 (CCT≥553.6 μm)(n=17 eyes)	p-value^*
Age (years) (Mean± SD)	58.89±10.46	60.47±7.45	0.610
CCT (μm) (Mean± SD)	513.74±14.48	579.59±21.17	>0.01
Initial IOP (mmHg) (Mean± SD)	17.05±0.85	17.47±0.72	0.122
Corrected IOP, Initial (mmHg) (Mean± SD)	18.08±0.85	15.76±1.17	>0.01
Average IOP (mm Hg) (Mean± SD)	13.58±1.07	14.82±1.07	>0.01
Corrected IOP, Average (mmHg) (Mean± SD)	14.97±0.92	12.64±1.25	>0.01
Follow up (months) (Mean± SD)	39.74±2.05	39.76±2.17	0.969

^* Statistical significance was tested by unpaired t-test.

Table 5.

Comparison of the number of OCT and an interval of OCT between thinner central corneal thickness group (Group 1) and thicker central corneal thickness group (Group 2)

	Group 1 (n=19)	Group 2 (n=17)	p-value^*
No. of OCT (Mean ± SD)	3.53 ± 0.51	3.47 ± 0.51	0.224
Interval of OCT (months) (Mean ± SD)	10.68± 2.24	11.06 ± 1.30	0.549
Interval of OCT (from initial to last, months) (Mean ± SD)	38.89 ± 1.37	38.18 ± 1.88	0.195

^* Statistical significance was tested by unpaired t-test.

Table 6.

Comparison of peripapillary retinal nerve fiber layer thickness between thinner central corneal thickness group (Group 1) and thicker central corneal thickness group (Group 2)

Peripapillary RNFL thickness	Group 1 (n=19)			Group 2 (n=17)			p-value^*
Peripapillary RNFL thickness	Initial exam	Last exam.	Change	Initial exam	Last exam.	Change	Initial exam	Last exam.	Change
Superior (μm)	98.11±15.83	87.37 ±18.37	−10.74±14.13	102.47±27.61	93.59 ±23.20	−9.00±9.08	0.572	0.376	0.668
Inferior (μm)	90.95±23.93	80.47 ±21.06	−10.47±13.50	112.88±9.78	104.77±8.39	−8.12±6.23	0.01	0.001	0.515
Nasal (μm)	63.26±16.79	58.32 ±14.26	−4.95±6.99	69.35±14.48	65.29±12.86	−4.06±3.36	0.255	0.134	0.626
Temporal (μm)	61.84±10.75	57.79±9.00	−3.95±4.13	70.18±16.72	64.18±12.86	−6.00±4.30	0.081	0.155	0.157
Average (μm)	78.52±11.20	72.07 ±11.71	−6.39±7.28	88.77±12.74	82.30 ±11.62	−5.47±4.73	0.015	0.007	0.661

^* Statistical significance was tested by unpaired t-test.

Table 7.

Multivariate hazard ratios and 95% confidence intervals for the progression of retinal nerve fiber layer damage

Baseline factors	Hazard ratio	95% Confidence interval	p-value^*
Thin central corneal thickness	5.36	0.63∼45.47	0.124
Sex (Male)	0.84	0.21∼3.39	0.80
Age (per 1 year older)	0.93	0.87∼1.00	0.06
Controlled intraocular pressure (per 1mmHg higher)	0.84	0.35∼2.04	0.71

^* Statistical significance was tested by cox regression.

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