An optic nerve injury may result in all of the following except.
**Core Concept**
Optic nerve injuries can cause various visual disturbances due to the complex anatomy and function of the optic nerve. The optic nerve is responsible for transmitting visual information from the retina to the brain, and damage to this nerve can result in a range of symptoms.
**Why the Correct Answer is Right**
The optic nerve is a critical structure for vision, and damage to it can result in visual field defects, including hemianopia (loss of half the visual field), quadrantanopia (loss of one-quarter of the visual field), and even complete blindness. The optic nerve also plays a role in the afferent pupillary defect (APD), where a pupil that reacts abnormally to light due to a problem with the afferent pathway.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect as optic nerve injuries can indeed cause visual disturbances, including visual field defects and blindness.
* **Option B:** This option is incorrect as optic nerve injuries can cause afferent pupillary defects, which are characterized by an abnormal pupillary reaction to light.
* **Option C:** This option is incorrect as optic nerve injuries can cause various visual disturbances, including visual field defects and blindness.
**Clinical Pearl / High-Yield Fact**
The afferent pupillary defect (APD) is a critical finding in patients with optic nerve injuries, and it can be diagnosed using the swinging-flashlight test. This test involves shining a light in the patient's eye and observing the pupillary reaction.
**Correct Answer: A. No visual disturbances.**