Cherry red spot is seen in
**Core Concept**
A cherry red spot is a clinical sign observed in certain conditions, characterized by a red discoloration of the macula, typically due to the presence of abnormal hemoglobin or lipid accumulation in the retinal tissue.
**Why the Correct Answer is Right**
The cherry red spot is most commonly associated with conditions that affect the retina, such as central retinal artery occlusion (CRAO), which leads to ischemia and an accumulation of oxygenated hemoglobin in the retinal tissue. The lack of blood flow results in a relative preservation of the retinal pigment epithelium's ability to metabolize the oxygen, causing the affected area to appear red. This is because the normal flow of blood is interrupted, leading to a buildup of oxygenated hemoglobin in the affected area, which gives the appearance of a cherry red spot.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not correct because a cherry red spot is not typically associated with conditions that primarily affect the optic nerve, such as optic neuritis.
**Option B:** This option is not correct because a cherry red spot is not typically associated with conditions that primarily affect the cornea, such as keratitis.
**Option C:** This option is not correct because a cherry red spot is not typically associated with conditions that primarily affect the lens, such as cataracts.
**Clinical Pearl / High-Yield Fact**
A key clinical pearl to remember is that a cherry red spot is often a sign of a vascular occlusion, such as CRAO, which requires prompt medical attention to prevent further vision loss.
**Correct Answer: D. Retinal detachment.**