Roopa Bharamshetter S1
BACKGROUND
Ethambutol causes retrobulbar neuritis that is related to the dose and duration of treatment, hence we undertook a prospective study of optic nerve function in patients on ethambutol.
MATERIALS AND METHODS
This study was conducted with a sample size of 100 patients. Patients diagnosed who were having tuberculosis and to be started on ethambutol along with other ATT drugs according to RNTCP regimen underwent detailed relevant history, examination and investigation. The best corrected Visual Acuity (VA), Colour Vision (CV) with Ishihara and visual field examination with Interzeag Octopus 1-2-3 automated perimeter were recorded and repeated every month. Mean Cumulative Dose (MCD) of ethambutol was calculated for each patient and statistical significance was done using Chi-square and paired t-test.
RESULTS
Out of 160 eyes (20 lost for follow up), 10 (6.25%) eyes developed Visual Field Defects (VFD) and abnormal VA was present in 10 (6.25%) eyes. MCD of patients with abnormal VA was more than MCD of patients with normal VA, but the difference was not statistically significant. CV abnormalities were present in 6 (3.7%) had strong association with VFD (p<0.00001) was dose dependent (p<0.001).
CONCLUSION
The study has demonstrated that visual field testing by automated perimetry is more sensitive and specific for detecting early ocular toxicity of ethambutol as compared to VA testing. The toxic effect of ethambutol on the eye can’t be predicted on an individual basis, there is a need for a complete ocular evaluation of every patient on ethambutol.
