Certified Ophthalmic Medical Technologist (COMT) Practice Exam

In latent nystagmus, in which direction is the fast phase expected to occur?

1. Away from the uncovered eye

2. Toward the uncovered eye

3. Randomly

4. In both directions

The correct answer is: Toward the uncovered eye

In latent nystagmus, the fast phase is expected to occur toward the uncovered eye. This phenomenon is specifically observed when one eye is covered; the remaining eye demonstrates nystagmus. The rationale behind this is linked to the neural pathways involved in eye movement control. When one eye is covered, the brain compensates by directing rapid movements toward the uncovered eye, resulting in a fast phase toward that eye. This is particularly notable in cases where there is a pre-existing ocular condition or structural asymmetry between the eyes. The underlying mechanism involves an imbalance in the neural signals controlling eye movements, which becomes more apparent when the visual input from one eye is removed. Hence, the fast phase does not occur randomly or in both directions. Understanding this characteristic of latent nystagmus is essential for clinicians as it can provide valuable insights into underlying conditions affecting visual processing and eye movement coordination.