J Korean Ophthalmol Soc.  2012 May;53(5):694-699.

Visual Function Test for Early Detection of Ethambutol-Induced Ocular Toxicity

• Chung JK
• Park YB
• Park SP

Abstract

PURPOSE
The purpose of the present study was to investigate various visual function tests for early detection of ethambutol-induced ocular toxicity.
METHODS
A prospective study of 20 eyes of 10 patients being treated with ethambutol was conducted. Visual acuity, visual field, color vision, fundus examination, contrast sensitivity, optical coherence tomography (OCT), and pattern-visual evoked potential (VEP) were assessed. Examinations were performed prior to therapy and every month for 5 months after treatment. VEP was performed every other month. The mean values of each parameter at each month were compared with the baseline examination and a p-value of <0.05 was considered significant. In addition, a greater than 2 standard deviation (SD) change in each parameter from the mean values at baseline was considered as an ocular toxicity induced change in each individual eye.
RESULTS
On OCT, a significant increase of the average retinal nerve fiber layer thickness was detected after 4 months of therapy. VEP showed an increased mean latency of the P100 wave after 2 and 4 months of therapy. However, a greater than 2 SD change from the mean values of the baseline was not observed on OCT, while 30% (6/20) of the eyes showed more than a 2 SD increase in VEP latency. Visual acuity, color vision, fundus, contrast sensitivity, and visual field were not affected in any patients.
CONCLUSIONS
The authors of the present study consider VEP as a sensitive test to detect early toxicity of ethambutol. VEP can be helpful in identifying subclinical ocular toxicity, especially in the high-risk patients.

Keyword

Early detection; Ethambutol; Ocular toxicity; Visual evoked potential

MeSH Terms

Color Vision
Contrast Sensitivity
Ethambutol
Evoked Potentials
Evoked Potentials, Visual
Eye
Humans
Nerve Fibers
Prospective Studies
Retinaldehyde
Tomography, Optical Coherence
Visual Acuity
Visual Fields
Ethambutol
Retinaldehyde