The Use of Optical Coherence Tomography in Patients With Ethambutol-induced Optic Neuropathy

Bu Ki Kim; Min Ahn

doi:10.3341/jkos.2010.51.8.1107

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Kim and Ahn: The Use of Optical Coherence Tomography in Patients With Ethambutol-induced Optic Neuropathy

Original Article

J Korean Ophthalmol Soc 2010;51(8):1107-1112.

Published online: 7 September 2010

DOI: https://doi.org/10.3341/jkos.2010.51.8.1107

The Use of Optical Coherence Tomography in Patients With Ethambutol-induced Optic Neuropathy

Bu Ki Kim, MD, Min Ahn, MD

Department of Ophthalmology, Chonbuk National University, Jeonju, Korea

Address reprint requests to Min Ahn, MD Department of Ophthalmology, Chonbuk National University Hospital #634-18, Geumam-dong, Deokjin-gu, Jeonju 561-712, Korea Tel: 82-63-250-1965, Fax: 82-63-250-1960, E-mail: ahnmin@chonbuk.ac.kr

Received 23 December 2009 Accepted 15 June 2010

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 evaluate the efficacy of optical coherence tomography (OCT) on diagnosis and follow-up in patients with ethambutol- induced optic neuropathy and to evaluate the prognosis of ethambutol-induced optic neuropathy.

Methods

Seven patients (14 eyes) with a history of ethambutol-induced optic neuropathy underwent best corrected visual acuity measurement (BCVA), visual field exam, fundus exam, and OCT at their first visit and again six months later.

Results

There was an overall statistically significant improvement in vision (p=0.001); however, two patients (four eyes) showed no improvement. A decrease in RNFL thickness was observed in all eyes. Additionally, there was a statistically significant decrease of 6.4 ± 5.37 μ m (6.8%) in the mean RNFL thickness (p=0.003), with the greatest decrease in the temporal quadrant, which showed a mean decrease of 6.1 ± 5.31 μ m (9.2%) (p＜0.001).

Conclusions

Optical coherence tomography may be not only a valuable tool in the quantitative and structural analysis of RNFL thickness in patients with ethambutol-induced optic neuropathy, but may also provide objective information on diagnosis and fol-low-up. Toxicity from ethambutol is reversible with discontinuation of the drug, and vision recovers gradually. However, impaired vision can remain even with cessation of ethambutol due to retinal nerve fiber damage.

Keywords: Ethambutol, Ethambutol induced optic neuropathy, Optical coherence tomography, Retinal nerve fiber layer

References

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Figure 1.

Retinal nerve fiber layer thickness in OCT scan and visual field defect of ethambutol-induced optic neuropathy patient (patient 2).

Table 1.

Clinical characteristics of five patients with ethambutol-induced optic neuropathy

	Patient 1	Patient 2	Patient 3	Patient 4	Patient 5	Patient 6	Patient 7
Age (yr)/gender	56/M	51/M	68/F	65/M	74/F	38/F	77/F
Duration of ethambutol treatment (months)	9	6	8	6	7	7	10
Duration of symptom before initial presentation (months)	1	1.5	2	1	0.5	2	1
Interval between cessation of ethambutol and initial presentation (wk) Initial examination (OD on top, OS on bottom)	1)	2	0	1	0	0	0.5
Visual acuity	20/400	20/200	20/200	20/400	20/400	20/100	20/200
	20/800	20/400	20/200	20/200	20/400	20/200	20/200
Mean deviation on HVF^*	−14.66	−23.59	−19.52	−13.94	−14.18	−9.54	−16.37
	−15.42	−25.77	−14.28	−14.51	−21.69	−11.32	−14.68
Optic disc appearance	Normal	Normal	Normal	Normal	Normal	Normal	Normal
	Normal	Normal	Normal	Normal	Normal	Normal	Normal
Average RNFL thickness (μ m)	94	81	97	85	109	92	97
	93	80	91	91	103	82	103
Examination after 6 months
Visual acuity	20/30	20/100	20/70	20/200	20/50	20/30	20/60
	20/30	20/100	20/50	20/200	20/40	20/40	20/60
Mean deviation on HVF	−6.42	−14.73	−10.47	−13.74	−9.14	−4.51	−7.57
	−5.41	−13.86	−8.84	−12.11	−13.65	−4.38	−17.72
Optic nerve appearance	Normal	Pale	Normal	Mildly pale	Normal	Normal	Normal
	Normal	Pale	Normal	Mildly pale	Normal	Normal	Normal
Average RNFL thickness	88	64	93	80	103	88	95
	90	63	86	83	99	80	98

^* HVF=Humphrey visual field.

Table 2.

Comparison of retinal nerve fiber layer thickness scanned at initial visit and 6 months follow-up

RNFL^* thickness (μ m)	Initial visit	6 months f/u	Difference (%)	p-value
Average	92.7 ± 8.74	86.3 ± 11.85	6.4 ± 5.37 (6.8)	0.003
Temporal	63.9 ± 14.29	57.8 ± 11.95	6.1 ± 5.31 (9.2)	<0.001
Superior	116.0 ± 13.62	108.0 ± 19.88	8.0 ± 12.2 (7.1)	0.014
Nasal	64.7 ± 9.69	62.6 ± 10.71	2.1 ± 5.99 (3.3)	0.102
Inferior	126.2 ± 16.05	117.0 ± 18.29	9.21 ± 9.97 (7.1)	0.002

^* RNFL=retinal nerve fiber layer.

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