The ocular features of retinitis pigmentosa include –
**Core Concept**
Retinitis pigmentosa (RP) is a group of genetic disorders affecting the retina's ability to respond to light, leading to progressive vision loss. It is characterized by degeneration of the photoreceptor cells (rods and cones) in the retina.
**Why the Correct Answer is Right**
The ocular features of RP include night blindness due to rod degeneration, followed by loss of peripheral and night vision. As the disease progresses, central vision is affected, leading to tunnel vision and eventual blindness. The characteristic "bone spicule" pattern of pigmentation in the retina, often seen in RP patients, is a result of the degeneration of the retinal pigment epithelium. This pattern is a result of the accumulation of lipofuscin and the subsequent proliferation of retinal pigment epithelial cells.
**Why Each Wrong Option is Incorrect**
**Option A:** RP is not typically associated with increased intraocular pressure (IOP). High IOP is more commonly seen in conditions like glaucoma.
**Option B:** RP does not typically present with nystagmus. Although some patients may exhibit nystagmus, it is not a characteristic feature of RP.
**Option C:** RP is not typically associated with strabismus. Although some patients may exhibit strabismus, it is not a characteristic feature of RP.
**Clinical Pearl / High-Yield Fact**
The "bone spicule" pattern in RP is a classic clinical finding that can be remembered using the mnemonic "BONES": Blue-black pigmentation, Ocular degeneration, Night blindness, Eyes affected, No central vision, Squinting (not a characteristic feature, but a common response to visual impairment).
**Correct Answer:** D.