Which statement accurately describes why dogs serve as a good model for human ocular surface disease compared with some other species?

• A. Canine meibum lipid composition is structurally and quantitatively comparable to humans.
• B. Rabbits are a better model because eyelid size is more similar to humans.
• C. Blink rates in dogs are identical to humans.
• D. Dogs cannot serve as models for human ocular surface disease.

Answer: (A)

The reason dogs are good models for human ocular surface disease relies on the tear film lipid layer, specifically the meibum secreted by the meibomian glands. If the canine meibum lipid composition is structurally and quantitatively similar to humans, the lipid layer that stabilizes the tear film behaves in a comparable way, influencing tear evaporation and surface wetting in parallel to humans. This similarity means disease processes driven by lipid abnormalities, such as evaporative dry eye, and the responses to treatments can translate more reliably from dogs to people. In contrast, relying on eyelid size similarity or other anatomical factors in species like rabbits does not address the essential tear film chemistry and gland function that drive ocular surface disease, so those choices are less informative for translational modeling. Blink rate differences exist across species and do not override the importance of matching tear film lipid biology. The statement that dogs cannot serve as models is not accurate given the shared lipid profile and resulting pathophysiology.