Which of the following medical instruments Is used to examine the retina?

An otoscope is used to examine the ear canal and eardrum. It allows healthcare providers to inspect for infections, blockages, or other abnormalities in the ear. While it is a valuable tool in otolaryngology, it is not suitable for examining the retina or any part of the eye.

A penlight is a small flashlight commonly used to illuminate areas for examination, such as the pupils of the eyes and oral cavity. While it can be used to perform a basic assessment of pupil response, it does not provide the detailed view of the retina that an ophthalmoscope does.

A spirometer measures lung function, specifically the volume and flow of air during breathing. It is primarily used in pulmonary medicine to assess respiratory conditions. This instrument is unrelated to eye examinations and does not aid in viewing the retina.

A tonometer measures intraocular pressure, which is essential for diagnosing glaucoma. Although it is related to eye health, it does not provide an examination of the retina itself and serves a different diagnostic purpose.