What is the primary use of retro illumination in an ophthalmic exam?

The primary use of retro illumination in an ophthalmic exam is indeed to reflect light against internal structures. This technique enhances the visibility of the ocular structures by utilizing a light source directed towards the eye from behind. As the light passes through, it highlights transparent structures such as the cornea, lens, and vitreous body, making it easier to observe abnormalities or conditions like cataracts, corneal opacities, or changes in the retina.

By achieving this reflection, veterinarians can better assess the integrity and health of internal structures without having to rely solely on direct visualization, which may not reveal subtle changes.

The other options involve different examination techniques or purposes. Assessing vision quality is typically done through specific tests unrelated to retro illumination, while checking for corneal abrasions usually involves direct examination techniques like fluorescein staining. Measuring intraocular pressure is done with tonometry and does not involve reflective light techniques. Thus, the role of retro illumination is distinct and focused on enhancing internal structure visibility.