Ophthalmology (Eye & Ear Hospital) - Theses
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ItemRetinal vascular changes in children: exploring the genesis of microvascular disease( 2015)BACKGROUND: Technological advances in computer-based analysis of retinal images have allowed reliable and precise measurements of subtle differences or changes in the retinal vascular geometry. One of the most well studied geometric parameters of the retinal vasculature is the caliber of the retinal vessels. Variations in retinal vascular caliber have been associated with a range of vascular risk factors, and may independently predict the risk of cardiovascular events (e.g., stroke, coronary heart disease) and ocular diseases (e.g., diabetic retinopathy, glaucoma). It is therefore believed that altered retinal vascular caliber could be an early sign of not only microvascular disease in the eye, but also subclinical systemic microvascular dysfunction, preceding the development of clinical cardiovascular diseases. However, previous studies have mostly focused on middle-aged to older adult populations, in which confounding effects of pre-existing systemic and ocular diseases are sometimes difficult to be completely adjusted for. Less is known about this important vascular parameter in children. In this project, we examined retinal vascular caliber in generally healthy children, and sought to further our fundamental understanding of the genesis of ocular and systemic microvascular disease. PURPOSE: The overall objective of this project is to examine retinal vascular caliber in generally healthy children, and determine its systemic and ocular associations. RESEARCH DESIGNS AND METHODS: The data used to assess the pattern and associations of retinal vascular caliber was from the Singapore Cohort Study of Risk Factors for Myopia (SCORM; mostly Asian Chinese) and the Sydney Childhood Eye Study (SCES; mostly Caucasians). The SCORM is a study of children aged 7 to 9 years recruited from 3 schools in Singapore. The SCES is a population-based study of 1,740 6-year-old children in Sydney, Australia. Retinal photographs from these two studies were used to measure retinal arteriolar and venular caliber using a semi-automatic computer-based program according to a validated and standardized protocol. All the participants from the SCORM and SCES undertook comprehensive and standardized medical history questionnaires, physical and eye examinations, and various other ophthalmic investigations, including optical coherence tomography and ocular response analyzer (for corneal biomechanical properties; in SCORM only). RESULTS: Retinal vascular caliber in children is normally distributed. The mean retinal arteriolar and venular caliber were 156.4μm (95% confidence interval [CI]: 155.4-157.3) and 225.4μm (95% CI: 224.1-226.8), respectively, in the SCORM; and 162.7μm (95% CI: 161.9-163.4) and 226.8μm (95% CI: 225.9-227.8), respectively, in the SCES. In both SCORM and SCES, narrower retinal arteriolar caliber was cross-sectionally associated with higher blood pressure, higher body mass index and indicators of poor in-utero growth (lower birth weight, lower birth length, smaller head circumference and/or preterm birth), whereas wider retinal venular caliber was associated with higher body mass index. For ocular associations, narrower retinal arteriolar and venular caliber were associated with smaller optic discs, thinner optic disc rims and retinal nerve fiber layer in both SCORM and SCES. Narrower retinal arteriolar caliber was associated with lower corneal dysteresis and corneal resistance factor in the SCORM. Axial length was not associated with retinal vascular caliber after correction of ocular magnification, and there was no association between retinal vascular caliber and intraocular pressure in the SCORM. CONCLUSIONS: Variations in retinal vascular caliber are associated with a range of ocular and systemic factors in generally healthy children. In view of the findings from studies of adult populations, the pattern of these associations seen in children suggests that retinal arteriolar narrowing and venular widening could be signs of physiological microcirculatory adaptation or subclinical microvascular dysfunction related to these ocular and systemic factors in early life.