Certified Ophthalmic Medical Technologist (COMT) Practice Exam

In assessing optic nerve head diseases, what is a common visual field finding?

1. Peripheral vision enhancement

2. Increased contrast sensitivity

3. Nasal step defect

4. Decreased visual acuity

The correct answer is: Nasal step defect

In the context of optic nerve head diseases, a nasal step defect is a notable visual field finding. This defect typically occurs when damage to the optic nerve leads to specific patterns of visual field loss. The nasal step refers to a marked decrease in sensitivity or a clear border in the visual field that often corresponds to an area where the nerve fiber layer of the retina has been affected, particularly in conditions like glaucoma. The nasal edge of the visual field starts to show a significant downturn or "step" due to this localized loss of retinal ganglion cells and the corresponding optic nerve fibers. Other visual field abnormalities can occur in optic nerve diseases, but the nasal step is particularly characteristic. For instance, peripheral vision enhancements and increased contrast sensitivity are not generally associated with optic nerve diseases. Instead, patients often experience a decrease in visual acuity due to the optic nerve's compromised function, but this is more of a general response and does not specifically highlight the unique manifestation of damage seen in the nasal step defect. Understanding this finding is crucial in diagnosing and managing optic nerve-related conditions effectively.