October - LRS Institute of Tuberculosis & Respiratory Diseases

VISUAL PATTERN IN ETHEMBUTOL TREATED TUBERCULAR PATIENTS 225
have been reported by many workers—Bhola
& Purhoit (1976), Citron (1969), Mathur &
Mathur (1981). The diminution in visual acuity
and peripheral field defects have been reported
as visual changes. The present study reveals a
change in visual pattern in the form of diminution
of visual acuity and change in normal
relative extent of green colour fields in 1.2%
patients treated with ethambutol, a finding
similar to that of Mathur & Mathur (1981).
Strikingly enough, in our study, no patient
complained of colour vision defect nor was it
evident on testing with Ishihara’s colour vision
charts. In the series reported by Mathur &
Mathur (1981) 6% patients were unable to
identify red and green colour on Ishihara’s
colour charts. This diminution of sensitivity
to green colour preceding that for blue colour
indicates the involvement of transmitting neural
apparatus, a change which may be evident
before the field for white shows demonstrable
alteration. The decrease in visual acuity and loss
of ability to perceive the colour green, has been
attributed to optic neuritis (Mathur & Mathur,
1981). Okcu (1975) and Schimidt (1966).
It was observed that the symptoms of visual
function disturbance following ethambutol
therapy disappeared within 2 to 5 months of
stopping the therapy on appearance of symptoms.
Of course, in both the symptomatic and asymptomatic
groups there was recordable functional
improvement, as well, following the cessation of
therapy.
Hence it is recommended that a regular
visual checkup be carried out in all the patients
put on ethambutol therapy, because the optic
nerve changes once produced are not reversible
except in mild and early cases, since once optic
nerve fibres degenerate they never regenerate
The patient must be primarily made aware
of the toxic symptoms which he may develop,
in which case he should report immediately
at the hospital. This will prevent any permanent
damage to vision due to ethambutol.
REFERENCES
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Ethambutol in tuberculosis patients. Ind. Jr. of
chest diseases & allied science; 1976, 18, 190.
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(supple, March).
3. Corpe, R.F. & Blalock F.A.: Retreatment of drag
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Ethambutol 1981, 29, 19.
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Ind. J. Tub., Vol. XXIX, No. 4