JCAT Independent Practice Exam 2025 – The All-in-One Guide to Exam Success!

The correct choice refers to a condition known as an afferent pupillary defect (APD), which occurs when there is an unequal amount of light information being transmitted to the brain from each eye. This discrepancy often arises due to damage in the sensory pathways that carry visual signals from the retina to the brain.

When light is shone in the affected eye with an APD, both pupils may constrict poorly or may even dilate, demonstrating a Marcus Gunn pupil reaction. In contrast, shining light in the unaffected eye typically results in a stronger response, as that eye transmits normal sensory input. This abnormal response indicates that the brain is receiving different levels of sensory information from the two eyes.

Other options, such as Adie's pupil or tonic pupil, are characterized by a singular pupil that is larger than normal and reacts sluggishly to light but are not necessarily defined by the differential light transmission between the two eyes. Third nerve palsy could result in an ocular misalignment or ptosis but is not primarily characterized by differential light perception as is seen in an afferent pupillary defect. Thus, the concept of unequal light transmission directly aligns with the definition of an afferent pupillary defect.