Hyaloid artery starts to regress at
**Core Concept**
The hyaloid artery is a major vascular structure in the developing eye, providing blood supply to the embryonic lens and vitreous body. Its regression is a critical process that occurs during fetal development.
**Why the Correct Answer is Right**
The hyaloid artery starts to regress around the 16th to 20th week of gestation, a process that is mediated by the degradation of the artery's endothelial cells and the subsequent invasion of fibroblasts. This regression is essential for the normal development of the retina and the vitreous body. The hyaloid artery's remnants eventually form the posterior vitreous body, which is a gel-like substance that fills the space between the vitreous and the retina.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the hyaloid artery's regression is not influenced by the development of the retinal vessels. The retinal vessels develop after the hyaloid artery has already formed and begun to regress.
* **Option B:** This option is incorrect because the hyaloid artery's regression is not a result of increased intraocular pressure. The regression of the hyaloid artery is a normal process that occurs regardless of intraocular pressure.
* **Option C:** This option is incorrect because the hyaloid artery's regression is not a result of genetic mutations. While genetic mutations can affect eye development, the regression of the hyaloid artery is a normal process that occurs in most individuals.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the remnants of the hyaloid artery can cause problems during cataract surgery, such as vitreous hemorrhage or retinal detachment. Understanding the normal regression of the hyaloid artery can help surgeons anticipate and prevent these complications.
**Correct Answer:** C. 20th week of gestation