Aim Ethambutol is one of the first-line drugs used to treat tuberculosis (TB) but its side effects include optic neuropathy, causing sight loss and changes in colour-vision. Early detection can mean any toxicity is reversible. Careful monitoring of sight is therefore required in patients taking ethambutol. After a patient irreversibly lost his sight from ethambutol toxicity and a successful claim was made against the hospital, more robust methods of monitoring eyesight were needed in patients taking ethambutol.

Method Currently in our department, all patients being started on ethambutol are referred to the ophthalmology department for baseline eye testing of visual acuity and colour vision. They are tested again at 4–6 months if they remain on ethambutol past 2 months. In between this, we previously relied on the patient reporting any change in vision to the TB team who would then arrange additional formal testing. To improve monitoring, we purchased two apps- a Munsell D15 Colour Vision Test and a LogMAR acuity test- to be used on an iPad. Four members of clinic staff were trained to use the apps. All patients on prolonged ethambutol now have their vision tested at all TB clinic appointments (usually monthly). Any change from previous or any problems detected by the apps mean stopping the ethambutol and urgent referral to ophthalmology for formal testing.

Outcomes In six months of using the apps, sixteen patients on ethambutol have had regular testing. Two patients have had changes in vision picked up by the apps. One patient’s formal eye testing showed no change. The other showed objective change in acuity and colour vision. Without using the apps, these changes may not have been picked up for several more weeks reducing the likelihood of reversibility. The apps are straightforward and a questionnaire of the staff trained in their use rated them easy to use.

Conclusion By using the apps, additional ophthalmology appointments are avoided unless needed and problems are potentially detected before the patient notices any change in their vision. Early detection enables ethambutol to be stopped with the aim of reversing any optic neuropathy before it becomes permanent.