A nurse is assessing a client who has tuberculosis and recently began taking ethambutol. The nurse should identify which of the following findings as an adverse effect of this medication?

Rationale: A. Blurred vision: Ethambutol is known to cause optic neuritis, which can lead to blurred vision, decreased visual acuity, and impaired red-green color discrimination. Clients on ethambutol should be monitored for changes in vision and advised to report any visual disturbances immediately. B. Tinnitus: Tinnitus is not a typical adverse effect of ethambutol. It is more commonly associated with other anti-tuberculosis drugs such as streptomycin, which can cause ototoxicity, especially affecting the auditory and vestibular systems. C. Peripheral edema: Peripheral edema is not commonly linked to ethambutol use. It may occur with certain cardiovascular medications or conditions but is not an expected side effect of this antitubercular drug. D. Bradycardia: Bradycardia is not a recognized adverse effect of ethambutol. This medication primarily affects the eyes rather than the cardiovascular system. Monitoring for vision changes is a higher priority when assessing for side effects.