Ethambutol (EMB, Myambutol) is regarded as one of the best tolerated tuberculostatics. Concerning to the side effects of EMB, the ocular disturbances are the only severe complication.
Recently, the author have a chance to evaluate ocular toxicity of the EMB. A total of 40 patients being treated with EMB, received a complete ophthalmic examination including visual acuity,. visual field, ophthalmoscopy and color vision test (by means of the Ishihara pseudoisochromatic plate, Farnsworth-Munsell 100 hue test)
Ocular toxicity occurred in four cases:
1. One was 18 yrs. old girl, two was fifth decade men and the other was 70 yrs. old man.
2. One case was bilateral renal tuberculosis and other cases were pulmonary tuberculosis.
3. Such patients received EMB daily in a single dose of 16 ?24mg/kg for a period of 4?17 months.
4. The ocular toxicity was manifested as follows:
1) loss of central vision in all cases
2) associated with a central scotoma in 3 cases and normal field in 1 case
3) marked decrease in color discrimination in all cases
4) fundus was normal in all cases
5. By the F-M test, EMB-induced acquired dyschromatopsia was detected, which was presented both graphically and numerically.
6. The F-M test permits early detection of the changes developing in the optic nerve and enables one to evaluate the dynamics of the toxic precess.
In patients treated with EMB, ophthalmic examination should be done prior to and in the course of therapy.
Owing to its sensitivity, the F-M test is of great value in the ophthalmic control examinations and early diagnosis can shorten the duration of complications involving the optic nerve.
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