Final answer:
In adults, noncomitant deviations are most commonly caused by cranial nerve palsies, thyroid eye disease, and myasthenia gravis. These conditions result in a misalignment of the eyes that varies with gaze direction or over time.
Step-by-step explanation:
Common Causes of Noncomitant Deviations in Adults
Noncomitant deviations are eye conditions where the degree of misalignment changes with gaze direction. In adults, the three most common causes of noncomitant deviations are:
- Cranial nerve palsies: This occurs when one or more of the cranial nerves (III, IV, VI) that control eye movement are impaired. This can lead to double vision and misalignment, varying in different gaze positions.
- Thyroid eye disease: Also known as Graves' ophthalmopathy, it can affect the extraocular muscles, causing them to swell and become restrictive. This might cause variable eye deviation angles depending on gaze direction.
- Myasthenia gravis: This autoimmune disorder affects the neuromuscular junction, which can lead to variable strength in the eye muscles, causing noncomitant eye deviations throughout the day.
Deviations from normal values could indicate active infections or blood-associated disorders. It's important for a healthcare professional to assess these signs as they could be associated with broader systemic issues.