Correct answer Image Quiz: A panting Great Dane with red eyes
Posterior segment (mass in the vitreous) is correct!
This dog does have all the listed signs. The diamond eye is an eyelid problem often seen in large-breed dogs. It is related to the exceeding laxity of the eyelid skin in which the upper eyelid has a shape of an upside down “V,” sometimes with consequent entropion, whereas the lower eyelid acquires the shape of a right side up “V,” with ectropion. This usually leads to conjunctivitis from continuous exposure, as demonstrated by the third eyelid chemosis and hyperemia. The iris lesion, with the different colors in the same iris, is normal (heterochromia iridis).
This dog had a tumor growing out of the ciliary body and touching the posterior aspect of the lens ventrally, hence the reason it could be seen with a naked eye (because of its proximity to the lens).
This case highlights the importance of a complete eye examination regardless of the presenting complaint. This animal had congestive heart failure, and the eye lesions were unrelated.