**Core Concept**
Chronic simple glaucoma, also known as primary open-angle glaucoma (POAG), is a progressive optic neuropathy characterized by a slow, irreversible loss of retinal ganglion cells, leading to visual field defects. The condition is often asymptomatic in its early stages, making regular visual field testing crucial for diagnosis and monitoring.

**Why the Correct Answer is Right**
The most common visual field defect in chronic simple glaucoma is a nasal step, which is a depression in the sensitivity of the visual field, particularly in the nasal hemifield. This defect is thought to result from the damage to the retinal nerve fiber layer, particularly the paracentral and arcuate scotomas. The nasal step is often associated with a characteristic pattern of field loss, where the sensitivity of the visual field is reduced in the nasal hemifield, but relatively preserved in the temporal hemifield.

**Why Each Wrong Option is Incorrect**
**Option A:** A baring scotoma is a type of visual field defect that is typically associated with retinal detachment or other retinal disorders, rather than glaucoma.
**Option B:** A cecocentral scotoma is a type of visual field defect that is typically associated with conditions such as optic neuritis or pituitary tumors, rather than glaucoma.
**Option C:** An altitudinal scotoma is a type of visual field defect that is typically associated with conditions such as ischemic optic neuropathy, rather than glaucoma.

**Clinical Pearl / High-Yield Fact**
In chronic simple glaucoma, the nasal step visual field defect is often associated with a characteristic pattern of field loss, where the sensitivity of the visual field is reduced in the nasal hemifield, but relatively preserved in the temporal hemifield. This pattern is often referred to as a "glaucomatous field defect".

**Correct Answer:** C.