[Macrophthalmos mimics microphthalmos in an 8-month-old Great Swiss Mountain Dog].

An 8-month-old Great Swiss Mountain dog was presented with a suspected right-sided microphthalmos, malformed and blind globe which was present since birth. On magnetic resonance imaging an ellipsoid macrophthalmos with absence of the normal retrobulbar tissue was detected. Histology revealed a dysplastic uvea with unilateral cyst formation associated with mild lymphohistiocytic inflammation. The ciliary body covered the posterior side of the lens unilaterally and showed focal metaplastic bone formation. Slight cataract formation as well as diffuse panretinal atrophy and intravitreal retinal detachment was evident. Preoperative diagnostic imaging procedure is recommended in eyes that clinically demonstrate as microphthalmos and are planned to be enucleated. As described in this case report the bulbus may be macrophthalmic which potentially complicates the enucleation. The performance of such a procedure at a site with ophthalmologic and soft tissue expertise is advisable. To the authors' knowledge this is the first report of a macrophthalmos with multiple ocular defects in a dog.