Which instrument is used for examining the internal structure of the eye?

The instrument primarily used for examining the internal structure of the eye is the ophthalmoscope. It is specifically designed to allow healthcare professionals to visualize the retina, optic nerve, and other internal components of the eye. When you look through an ophthalmoscope, it illuminates and magnifies these structures, enabling a detailed examination that is vital for diagnosing various eye conditions and diseases, such as diabetic retinopathy, glaucoma, and macular degeneration.

Other instruments serve different functions; for example, a tonometer measures intraocular pressure, which is crucial for assessing glaucoma risk but does not provide visual access to the eye’s internal structures. A retinoscope is used to determine refractive errors by assessing how light reflects off the retina, while an autorefractor automates the process of measuring refractive error by projecting light into the eye. However, neither of these instruments is designed for the direct examination of internal eye structures. Thus, the ophthalmoscope is the most appropriate choice for the specified task.