Final answer:
The ophthalmoscope is the correct instrument for retinal testing. It allows examination of the retina and other internal structures of the eye, which is essential for detecting conditions like glaucoma.
Step-by-step explanation:
The correct option : a
The most appropriate instrument for retinal testing is the ophthalmoscope. This device enables healthcare professionals to examine the interior surfaces of the eye, including the retina, optic disc, choroid, and blood vessels. It's crucial for detecting conditions such as glaucoma, where checking the optic nerve for signs of damage is imperative. Regular eye examinations using an ophthalmoscope can help detect glaucoma early, which is especially important for people over 40 who are at an increased risk of developing this eye disease.
While other instruments mentioned, such as the stethoscope, sphygmomanometer, and otoscope, have their specific uses in healthcare, they are not used for examining the retina. The stethoscope is used to listen to the internal sounds of the body, primarily the heart and lungs. The sphygmomanometer measures blood pressure, and the otoscope allows examination of the ear canal and eardrum. Therefore, none of these tools are suitable for retinal testing.