**Core Concept**
Retinitis pigmentosa is a group of genetic disorders that affect the retina's ability to respond to light, leading to progressive vision loss. It is characterized by the degeneration of rod photoreceptors, which are responsible for peripheral and night vision.

**Why the Correct Answer is Right**
The characteristic finding of retinitis pigmentosa is the presence of **bone spicule pigmentation**, which is a result of the accumulation of lipofuscin in the retinal pigment epithelium. This type of pigmentation is caused by the degeneration of rod photoreceptors, leading to the formation of characteristic "bone spicule" patterns in the mid-peripheral retina. The loss of rod photoreceptors also leads to **night blindness**, which is a hallmark symptom of retinitis pigmentosa.

**Why Each Wrong Option is Incorrect**
**Option A:** Retinal detachment is a complication of retinitis pigmentosa, but it is not a characteristic finding.
**Option B:** Optic atrophy may occur in advanced cases of retinitis pigmentosa, but it is not a specific characteristic finding.
**Option C:** Macular degeneration is a separate condition that can cause vision loss, but it is not typically associated with retinitis pigmentosa.

**Clinical Pearl / High-Yield Fact**
Retinitis pigmentosa is often inherited in an autosomal dominant pattern, but it can also be inherited in an autosomal recessive or X-linked pattern. The disease is caused by mutations in genes that code for proteins involved in phototransduction, such as rhodopsin and peripherin.

**Correct Answer: D. Bone spicule pigmentation.**