What does retroillumination detect?

Retroillumination is a specialized optical technique used primarily in ophthalmology to evaluate the condition of the eye's structures. This method involves shining a light through the pupil and using the reflection off the retina to assess various components of the eye.

The correct answer focuses on the ability of retroillumination to detect opacities or defects in the lens. When this technique is employed, any abnormalities within the lens, such as cataracts or other forms of opacification, can be identified. This is due to the contrast created by the light's reflection; opacities will disrupt the normal transmission of light, thus appearing differently compared to a clear lens in the retroillumination view.

Other options pertain to different aspects of ocular pathology. Retinal aneurysms, optic nerve damage, and corneal scratches would typically be diagnosed using other techniques, such as direct ophthalmoscopy, visual field tests, or slit-lamp examinations. These methods are more suited for assessing the conditions associated with the retina, optic nerve, and cornea respectively, highlighting the specific application of retroillumination in identifying lens-related issues.