An ivy pot that looks full on one side and sparse on the other may be responding to uneven light. Check the position before cutting every trailing stem back to the same length.
Look at where the new growth is heading. A shelf beside a window can light one side while leaving the opposite side shaded, particularly when curtains or nearby plants block part of the opening.
Correct the display gradually
Choose a position suited to the identified ivy and make changes without suddenly exposing a shaded plant to harsh sun. Turn the pot as needed to manage its outline, while keeping access for watering and inspection.
Long stems can be arranged or trimmed, but trimming does not replace suitable light. Remove dead material and inspect the remaining leaves, especially their undersides and the points where stems meet.
If the plant has also been losing leaves, check moisture and temperature. A pot beside glass may experience a different night-time environment from one farther inside the room. Note those conditions rather than assuming an uneven shape has one cause. Judge the improvement from the next growth the plant produces.
Related reading: Indoor Ivy Care: Light, Watering, Feeding and Trimming.