Ethambutol is widely used as first-line drug, but has serious side effect of optic neuropathy. As previously reported, incidence of ethambutol optic neuropathy is about 1~2%, there was considerable screening efforts and medical cost is increasing. However, there is no effective treatment of ethambutol optic neuropathy or no definite preventable measure. Moreover, multi-drug resistance tuberculosis or extensively drug resistance tuberculosis is emerging, more toxic secondary drug is used in the long-term.

It is known that retinal nerve fiber layer is increased early stage in ethambutol optic neuropathy. So we decide to evaluate the retinal nerve fiber layer thickness measured by optical coherence tomography in longitudinal manner.

Inclusion Criteria:

1. Primary lung tuberculosis who has not previously treated
2. Age more than 19 years and less than 70 years old

Exclusion Criteria:

1. spherical equivalent more than +6.00 diopter or less than -6.00 diopter by autorefraction
2. Closed angel or intraocular pressure more than 21 mmHg
3. Best corrected visual acuity less than 0.5 with severe cataract
4. Retinal disorder include branch retinal vein occlusion, diabetic macular edema, wet-type age-related macular degeneration
5. Age less than 20 years or older than 70 years old
6. Any intraocular surgery less than 3 months
7. Intellectual problems or illiterate whom could not obtained informed consent

patients who diagnosed with primary lung tuberculosis