This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Vitreous and retina, Subject name: Ophthalmology
Degree of diabetic retinopathy depends on - 
Select and explain. 
A. Type of disease, B. Duration of disease, C. Severity of disease, D. Retinal involvement
B: Duration of disease
Answer: B: Duration of disease 
Explanation: Microaneurysms in the macular area (the earliest detectable lesion).  Retinal haemorrhages both deep (dot and blot haemorrhages) and superficial haemorrhages (flame-shaped).  Hard exudates-yellowish-white waxy-looking patches are arranged in clumps or in circinate pattern. These are commonly seen in the macular area.  Retinal oedema characterized by retinal thickening.  Cotton-wool spots (if > 8, there is high risk of developing PDR).  Venous abnormalities, beading, looping and dilatation.  Intraretinal microvascular abnormalities (IRMA).  Dark-blot haemorrhages representing haemorr- hagic retinal infarcts. On the basis of severity of the above findings the NPDR has been fuher classified as under: 1. Mild NPDR  At least one microaneurysm or intraretinal hemorrhage.  Hard/soft exudates may or may not be present. 2. Moderate NPDR  Moderate microaneurysms/intraretinal hemorr- hage.  Early mild IRMA.  Hard/soft exudates may or may not present. 3. Severe NPDR. Any one of the following  Four quadrants of severe microaneurysms/ intraretinal hemorrhages.  Two quadrants of venous beading.  One quadrant of IRMA changes. 4. Very severe NPDR. Any two of the following  Four quadrants of severe microaneurysms/ intraretinal hemorrhages.  Two quadrants of venous beading.  One quadrant of IRMA changes. Ref Comprehensive ophthalmology AK Khurana 4th edition page no 494