You are presented with multiple paper abstracts, alongside the associated literature review and chapter titles. Given the provided information, you are going to do a literature review. Please generate a coherent literature review that synthesizes the content, draws connections between different works, highlights major findings, and identifies any gaps in the existing research.

Literature Review Title: A Review on the Extraction of Quantitative Retinal Microvascular Image Feature 
Chapter Title:  Focal Arteriolar Narrowing Measurement. 
1. Abstract of Cited Paper (BIB001):  Background and Purpose— Deep intracerebral hemorrhage (ICH) and lacunar infarcts are the result of small vessel disease, whereas nonlacunar infarcts are often caused by large artery atherosclerosis or cardiac embolism. We hypothesized that patients with deep ICH and lacunar infarcts have similar retinal microvascular signs and that these differ from those seen in patients with nonlacunar infarcts. Methods— We studied patients with acute stroke and classified their stroke as deep ICH, lacunar infarction, or nonlacunar infarction. In a masked fashion we assessed retinal photographs for quantitative and qualitative evidence of microvascular damage. Results— We recruited 630 patients (51 had deep ICH, 93 had lacunar infarction, and 486 had nonlacunar infarction). Patients with deep ICH were more likely than those with nonlacunar infarcts to have severe focal narrowing of the retinal arterioles (OR, 3.7), severe arteriovenous nicking (OR, 2.6), and quantitatively narrower retinal arterioles and wider retinal v...

Literature Review:
Focal arteriolar narrowing is also a symptom for the early detection of hypertension and acute stroke. Focal arteriolar narrowing generally occurs with the increasing arteriolar blood pressure from 130mm Hg to 160mm Hg that affects the arteriolar wall BIB002 . The study of BIB001 investigated the relationship between the arteriolar narrowing and hypertension and found that the hypertension increasing rate is higher among the people with arteriolar narrowing. Figure 6 shows the focal arteriolar narrowing in fundus retinal image.