Answer
Please see the work below.
Work Step by Step
We know that $\theta_{min}=\frac{1.22\lambda}{D}$. This equation shows that larger the diameter of the aperture, the smaller the angular separation and as a result, we have a greater resolution. A cat's eye has a greater aperture (D) in the vertical direction; hence its resolution is high in the vertical direction as compared to that of the horizontal direction.
