The relationship between carotid plaque composition, plaque morphology, and neurologic symptoms.

Variations in plaque composition could make carotid artery plaques prone to ulceration, subintimal hemorrhage, plaque progression, or embolization and, thus, increase the risk of ipsilateral ischemic neurologic events. Seventy-eight carotid endarterectomy specimens from 74 patients (38 symptomatic and 36 asymptomatic) were analyzed. Prior to analysis, 43 of the 78 plaques were divided into sections based on disease severity and examined by light microscopy for surface ulceration and subintimal hemorrhage. Extracted lipid, cholesterol, collagen, and calcium content were determined in all 78 plaques and compared to clinical presentation and/or morphologic observations. Plaques removed from symptomatic patients contained more extracted lipid and cholesterol than those from asymptomatic patients. In addition, compared to the remainder of the plaque, the most stenotic portion of the plaque contained more cholesterol, more calcium, and less collagen. Finally, irrespective of clinical presentation, plaque sections found to have surface ulceration and subintimal hemorrhage contained more cholesterol and less collagen than plaques without these changes. Lipid-laden plaques with low levels of collagen are associated with plaque ulceration, subintimal hemorrhage, and ischemic neurologic symptoms. This suggests that plaque composition may be an important factor in the pathophysiology of carotid atherosclerosis.

Optic nerve crescents and refractive error.

In this paper we discuss whether the presence of an optic nerve crescent might affect the way in which axial length and corneal curvature interact to determine refractive error. Subjective refraction, keratometry, measurement of body height, axial length of the eye, and stereophotography of the optic nerves were performed on 224 subjects, 8- to 25-years-old. Photographs were examined under magnification; optic nerve crescents, if present, were measured in the horizontal dimension. Those measurements were then corrected for magnification due to the eye and the camera. Logistic regression analysis suggested that male gender and myopic refractive error were most directly associated with the presence of a large crescent, whereas axial length, age, and horizontal keratometry reading were less directly associated with the presence of a crescent. The relation between axial length and refractive error differed among those with large crescents compared to those with small or no crescents. Simple regression showed that, for those with a crescent at least 0.2-mm wide, a 1-mm greater axial length was associated with, on the average, 1.26 D of myopia. For those with smaller or no crescents, a 1-mm greater axial length was associated with only 0.66 D of myopia. This difference was statistically significant at the 0.02 level of confidence.

Refractive error, axial length, and height as a function of age in young myopes.

Classical studies suggest that growth of the eye as assessed by axial elongation ceases by 13 years of age. The subjects in these studies were mostly emmetropes. In contrast, the childhood progression of myopia continues to the middle to late teenage years. We collected cross-sectional data on refractive error, axial length, and height. Analysis of these data based on a linear regression model suggests that axial elongation continues later in myopes than the classical studies suggest. The age of cessation of axial elongation in myopes was earlier in females than in males. For both sexes, the ages of axial elongation cessation in myopes were similar to the ages of cessation of increases in height.

Lipid risk factors in patients requiring arterial reconstruction.

Progressive peripheral atherosclerosis commonly leads to failure of a bypass graft. Lowering blood cholesterol retards coronary atherosclerosis and similar treatment might limit peripheral atherosclerosis. To identify lipid risk factors for peripheral atherosclerosis, 144 patients with peripheral atherosclerosis (98 with severe disease and 46 with stable claudication) and 61 age-matched control subjects were studied. Fasting lipid (cholesterol and triglycerides) and lipoprotein (high-density lipoprotein [HDL], low-density lipoprotein [LDL], and very-low-density lipoprotein [VLDL] cholesterol [C]) levels were measured. The incidence of hypertension and diabetes mellitus, amount of previous tobacco use, and location and severity of the peripheral atherosclerosis were also determined. Patients with peripheral atherosclerosis had higher VLDL-C and lower HDL-C levels than controls had, but serum cholesterol and plasma LDL-C levels were similar. Patients with peripheral atherosclerosis also had a higher incidence of diabetes mellitus and hypertension. Predictors of peripheral atherosclerosis by regression analysis were diabetes mellitus, low HDL-C levels, and tobacco use, with diabetes mellitus being the strongest variable. Peripheral atherosclerosis below the inguinal ligament was strongly predicted by low HDL-C and increased VLDL-C levels but not by increased cholesterol or LDL-C levels. Thus lipid risk factors for peripheral atherosclerosis are different, and attempts at limiting late graft failure by lowering lipid levels should be directed toward these lipoproteins.