So far, we’ve learned to diagnose and treat diseases of many different organs. However, I think the eyes are the most unique in that we can directly observe most of the pathology in them with our bare eyes or with the assistance of simple instruments. Of course, sometimes we do need to use more advanced diagnostic techniques.
There is an old saying that goes “The eye is the window to the soul.” Not only can you tell one’s emotion by looking at their eyes, you can also tell a lot about their health status by examining their eye. The eyes can tell you lots about the brain. When we are doing an ophthalmic exam, we check the reflexes to identify any abnormalities in sensation, ability to blink, the coordination between the eye and the brain, etc. Lesions in the eye may be secondary to lesions in the brain. For example, a patient with corneal ulcers may have a disease in the brainstem that affects his/her ability to blink hence the development of a corneal ulcer. Other systemic diseases may also manifest as abnormalities in the eyes – inflammation or bleeding in the eye may be associated with inflammation or bleeding in other areas in the body, respectively.
In addition to pathologic changes, changes in the eye that are normal variations could be super cool to look at. For instance, the fundus of the eye of an albino animal is mainly red and white versus the fundus of a normal dog may show different colors of green, brown, red, etc.
The eyes can also tell you lots about the animals. For prey species, their eyes are located more towards the sides so that they have a more panoramic view to detect predators. For predator species, their eyes are located more towards the midline of the face so that they have a better perception of depth hence a more precise appreciation of where the prey is.