Repetitive eye movements with repeated pulling of one or more of the eye muscles is a major factor responsible for ocular tendonitis. Try this to test your eye muscle stamina. Look at something on the ceiling right, then to ceiling left and then to an object on the floor right and then looking to the floor left. Continue looking in this manner for a few minutes. You will soon notice that the eyes become heavy and tired. If you continue longer, eventually the tendons will become sore and achy. Eye Muscle Imbalance Another cause of ocular tendonitis is constant muscle tension caused by the misalignment of the eyes or eye muscle imbalance. When the eyes are not aligned and the images pull apart, the eye muscles are compelled to realign them. If they do not, then double vision occurs. The misalignment can cause a constant pulling of one or more specific muscles. These muscular efforts become more difficult as vision tasks become more complex and take longer to perform.