Commonest cause of loss of vision in non-proliferative diabetic retinopathy is:
**Core Concept**
Non-proliferative diabetic retinopathy (NPDR) is a complication of diabetes characterized by microvascular damage to the retina, leading to vision impairment. The common causes of vision loss in NPDR involve damage to the retinal vasculature, which can result in ischemia, edema, and neovascularization.
**Why the Correct Answer is Right**
The correct answer is **retinal ischemia**. Retinal ischemia occurs due to the narrowing or closure of retinal capillaries, leading to reduced perfusion and oxygen delivery to the retina. This can cause damage to the retinal nerve fiber layer and ganglion cells, resulting in vision loss. The ischemia can also stimulate the release of angiogenic factors, promoting neovascularization, but this is more characteristic of proliferative diabetic retinopathy.
**Why Each Wrong Option is Incorrect**
* **Option A:** Diabetic macular edema (DME) is a common complication of NPDR, but it is not the most common cause of vision loss. DME can cause vision loss due to fluid accumulation in the macula, but it is often treatable with anti-vascular endothelial growth factor (anti-VEGF) therapy.
* **Option B:** Neovascularization is a characteristic of proliferative diabetic retinopathy, not NPDR. While neovascularization can cause vision loss, it is not the most common cause in NPDR.
* **Option D:** Vitreomacular traction (VMT) can cause vision loss, but it is not a direct consequence of NPDR. VMT is a separate entity that can be caused by various factors, including age-related macular degeneration and epiretinal membrane formation.
**Clinical Pearl / High-Yield Fact**
The Early Treatment Diabetic Retinopathy Study (ETDRS) demonstrated that timely treatment of diabetic retinopathy can reduce the risk of vision loss. Patients with NPDR should be screened regularly for signs of disease progression, including retinal ischemia, DME, and neovascularization.
**Correct Answer:** C. Retinal ischemia.