Changes in refractive error over a 5-year interval in the Beaver Dam Eye Study.
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PURPOSE: To examine changes in spherical equivalent over a 5-year period in persons 43 to 84 years of age. METHODS: All people 43 to 84 years of age and living in Beaver Dam, Wisconsin, in 1988 were invited for a baseline examination (1988-1990) and a 5-year follow-up examination (1993-1995). Refractions were determined according to the same protocol at both examinations. Aphakic and pseudophakic eyes were excluded as well as eyes with best corrected Snellen visual acuity of 20/40 and worse. After exclusions, refraction was obtained on 3007 right eyes and 3012 left eyes of the 3684 people participating in both examinations. RESULTS: Right and left eyes behaved similarly. Spherical equivalent became more positive in the youngest subjects and more negative in older subjects. After adjusting for other factors, the 5-year change in spherical equivalent of those 45, 55, 65, and 75 years of age was +0.15, +0.18, +0.10, and -0.07D, respectively. Severity of nuclear sclerosis was related to the amount of change. Those with mild nuclear sclerosis at baseline had a change of +0.2 D, whereas those with severe nuclear sclerosis had a change of -0.5 D. The amount of change was also related to gender, diabetes, and age at onset of myopia. It was unrelated to education and baseline spherical equivalent. CONCLUSIONS: Changes in spherical equivalent over a 5-year period were small. Before the age of 70, people became more hyperopic. After the age of 70, people became more myopic. Much of the myopic change may be related to increasing nuclear sclerosis. (+info)
Direct evidence for immiscible cholesterol domains in human ocular lens fiber cell plasma membranes.
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The molecular structure of human ocular lens fiber cell plasma membranes was examined directly using small angle x-ray diffraction approaches. A distinct biochemical feature of these membranes is their high relative levels of free cholesterol; the mole ratio of cholesterol to phospholipid (C/P) measured in these membranes ranges from 1 to 4. The organization of cholesterol in this membrane system is not well understood, however. In this study, the structure of plasma membrane samples isolated from nuclear (3.3 C/P) and cortical (2.4 C/P) regions of human lenses was evaluated with x-ray diffraction approaches. Meridional diffraction patterns obtained from the oriented membrane samples demonstrated the presence of an immiscible cholesterol domain with a unit cell periodicity of 34.0 A, consistent with a cholesterol monohydrate bilayer. The dimensions of the sterol-rich domains remained constant over a broad range of temperatures (5-20 degrees C) and relative humidity levels (31-97%). In contrast, dimensions of the surrounding sterol-poor phase were significantly affected by experimental conditions. Similar structural features were observed in membranes reconstituted from fiber cell plasma membrane lipid extracts. The results of this study indicate that the lens fiber cell plasma membrane is a complex structure consisting of separate sterol-rich and -poor domains. Maintenance of these separate domains may be required for the normal function of lens fiber cell plasma membrane and may interfere with the cataractogenic aggregation of soluble lens proteins at the membrane surface. (+info)
Risk factors for cortical, nuclear, and posterior subcapsular cataracts: the POLA study. Pathologies Oculaires Liees a l'Age.
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The POLA (Pathologies Oculaires Liees a L'Age) Study is a population-based study of cataract and age-related macular degeneration and their risk factors being carried out among 2,584 residents of Sete, southern France, aged 60-95 years. Recruitment took place between June 1995 and July 1997. Cataract classification was based on a standardized lens examination by slit lamp, according to Lens Opacities Classification System III. This paper presents results obtained from cross-sectional analysis of the first phase of the study. In polytomous logistic regression analyses, an increased risk of cataract was found for female sex (cataract surgery: odds ratio (OR) = 3.03; cortical cataract: OR = 1.67), brown irises (cortical, nuclear, and mixed cataracts: OR = 1.61), smoking (cataract surgery: OR = 2.34 for current smokers and OR = 3.75 for former smokers), known diabetes of 10 or more years' duration (posterior subcapsular, cortical, and mixed cataracts and cataract surgery: OR = 2.72), use of oral corticosteroids for at least 5 years (posterior subcapsular cataract: OR = 3.25), asthma or chronic bronchitis (cataract surgery: OR = 2.04), cancer (posterior subcapsular cataract: OR = 1.92), and cardiovascular disease (cortical cataract: OR = 1.96). Decreased risk of cataract was found with higher education (all types of cataract and cataract surgery: OR = 0.59), hypertension (cataract surgery: OR = 0.57), and high plasma retinol levels (nuclear and mixed cataracts and cataract surgery: OR = 0.75 for a 1-standard-deviation increase). Most of the risk factors identified in this study confirm the findings of other studies. The association of cataract with plasma retinol level requires further investigation. (+info)
3 year simvastatin treatment and lens nuclear back scattering.
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AIM: To determine if 3 year treatment of hypercholesterolaemia with simvastatin causes an increase of lens nuclear back scattering. METHODS: 160 patients with hypercholesterolaemia in the Scandinavian Simvastatin Survival Study (4S) were followed for 3 years. Half (80) of the patients took simvastatin and half (80) received placebo. The lens was photographed with a Topcon SL-45 slit lamp camera at the beginning and at 1 year intervals. A common lens nuclear area was used for measuring lens nuclear back scattering. RESULTS: Nuclear back scattering increased with age and there was more pronounced scattering in women than in men. Lens nuclear back scattering did not differ significantly between the simvastatin and placebo groups, but the power was low (0.2). Lens nuclear back scattering increased during the study period independently of baseline back scattering, age, and sex for both groups. CONCLUSION: Although no significant difference was found between the simvastatin and placebo groups, the currently available data are insufficient for exclusion of the possibility that taking simvastatin during a 3 year period increases nuclear back scattering. However, a possible minor increase of nuclear back scattering is clinically irrelevant considering known beneficial effects of simvastatin on coronary heart disease. (+info)
Genetic and environmental factors in age-related nuclear cataracts in monozygotic and dizygotic twins.
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BACKGROUND: Age-related cataracts are a major public health problem. The relative importance of genes and environment in the causation of nuclear cataracts, the most common form of age-related cataracts, is not known. METHODS: We studied 506 pairs of female twins (226 monozygotic and 280 dizygotic) who were 50 to 79 years old (mean, 62). The amount of nuclear cataract in the right and left eyes was determined objectively by analysis of Scheimpflug lens photographs (yielding three measures) and subjectively with use of the Oxford Clinical Cataract Classification and Grading System (yielding one measure). All eight measures (four in each eye) were subsequently combined in one summary measure of nuclear cataract for each woman. A univariate maximum-likelihood model was used to estimate the variance of the genetic and environmental contributions to each of the measures. RESULTS: The different measures of cataract formation were highly correlated (correlation coefficients, 0.71 to 0.94). The mean scores were similar for the right and left eyes and for monozygotic and dizygotic twins. Quantitative genetic modeling of each of the nuclear-cataract scores invariably resulted in a best-fitting model that involved additive genetic effects, unique environmental effects, and age. The common environmental and dominant genetic effects could be removed from the models without significant loss of fit. The overall heritability in the combined nuclear-cataract score (the proportion of the variance explained by genetic factors) was 48 percent (95 percent confidence interval, 42 to 54 percent); age accounted for 38 percent of the variance (95 percent confidence interval, 31 to 44 percent) and unique environmental effects for 14 percent (95 percent confidence interval, 12 to 18 percent). CONCLUSIONS: Genetic effects are important even in such a clearly age-related disease as nuclear cataract, explaining almost 50 percent of the variation in the severity of this disease. (+info)
Incidence and management of posteriorly dislocated nuclear fragments following phacoemulsification.
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PURPOSE: To report the incidence, management and complications of nucleus dislocation into the vitreous during phacoemulsification. METHODS: Retrospective review of 1250 consecutive phacoemulsification performed by consultants and residents in a teaching hospital. RESULTS: The incidence of nucleus drops was 0.8% (10 out of 1250). Loss of nuclear fragments occurred during phacoemulsification in 9 patients. In one, the dislocation was caused by hydro-dissection. All except one patient (who refused further intervention) underwent pars plana vitrectomy with removal of nuclear fragments. Eight of them had intraocular lens (IOL) inserted at the time of cataract surgery or at vitrectomy; one patient was scheduled for a secondary IOL. Postoperative best corrected visual acuity ranged from 6/24-6/6; 8 patients achieved a vision of 6/12 or better. Complications included cystoid macular oedema (5 patients), retinal break (1 patient) and retinal detachment (1 patient). CONCLUSION: Appropriate management of posteriorly dislocated nucleus can restore good visual acuity. The use of phacoemulsification mandates availability of referral facilities for management of complications. (+info)
Impact of aging and hyperbaric oxygen in vivo on guinea pig lens lipids and nuclear light scatter.
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PURPOSE: To measure lipid compositional and structural changes in lenses as a result of hyperbaric oxygen (HBO) treatment in vivo. HBO treatment in vivo has been shown to produce increased lens nuclear light scattering. METHODS: Guinea pigs, approximately 650 days old at death, were given 30 and 50 HBO treatments over 10- and 17-week periods, respectively, and the lenses were sectioned into equatorial, cortical, and nuclear regions. Lipid oxidation, composition, and structure were measured using infrared spectroscopy. Phospholipid composition was measured using (31)P-NMR spectroscopy. Data were compared with those obtained from lenses of 29- and 644-day-old untreated guinea pigs. RESULTS: The percentage of sphingolipid approximately doubled with increasing age (29-544 days old). Concomitant with an increase in sphingolipid was an increase in hydrocarbon chain saturation. The extent of normal lens lipid hydrocarbon chain order increased with age from the equatorial and cortical regions to the nucleus. These order data support the hypothesis that the degree of lipid hydrocarbon order is determined by the amount of lipid saturation, as regulated by the content of saturated sphingolipid. Products of lipid oxidation (including lipid hydroxyl, hydroperoxyl, and aldehydes) and lipid disorder increased only in the nuclear region of lenses after 30 HBO treatments, compared with control lenses. Enhanced oxidation correlated with the observed loss of transparency in the central region. HBO treatment in vivo appeared to accelerate age-related changes in lens lipid oxidation, particularly in the nucleus, which possesses less antioxidant capability. CONCLUSIONS: Oxidation could account for the lipid compositional changes that are observed to occur in the lens with age and cataract. Increased lipid oxidation and hydrocarbon chain disorder correlate with increased lens nuclear opacity in the in vivo HBO model. (+info)
Attributable risk estimates for cataract to prioritize medical and public health action.
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PURPOSE: Cataract is the most common cause of blindness in the world. The purpose of this study was to estimate the population attributable risk associated with identified risk factors for cortical, nuclear, and posterior subcapsular (PSC) cataract in a representative sample of the Victorian population aged 40 years and older. METHODS: Cluster, stratified sampling was used and participants were recruited through a household census. At locally established test sites, standardized clinical examinations were performed to assess cataract and personal interviews were conducted to quantify potential risk factors. Multivariate logistic regression was used to determine the independent risk factors associated with the three types of cataract, and the population attributable risk was calculated. RESULTS: A total of 3271 (83% of eligible) of the urban residents and 1473 (92%) rural residents participated. The urban residents ranged in age from 40 to 98 years (mean, 59 years), and 1511 (46%) were men. The rural residents ranged in age from 40 to 103 years (mean, 60 years), and 701 (48%) were men. The overall prevalence of cortical cataract was 12.1% (95% CL 10.5, 13.8), nuclear cataract 12.6% (95% CL 9.61, 15.7), and PSC cataract 4.93% (95% CL 3.68, 6.17). Significant risk factors for cortical cataract included age, female gender, diabetes for greater than 5 years, gout for greater than 20 years, arthritis, myopia, average annual ocular UV-B exposure, and family history of cataract (parents or siblings). Significant risk factors for nuclear cataract included age, female gender, rural residence, age-related maculopathy, diabetes for greater than 5 years, smoker for greater than 30 years, and myopia. The significant risk factors for PSC cataract were age, rural residence, thiazide diuretic use, and myopia. Of the modifiable risk factors, ocular UV-B exposure explains 10% of the cortical cataract in the community, and cigarette smoking accounts for 17% of the nuclear cataract. CONCLUSIONS: Because of the near universal exposure to UV-B in the environment, ocular protection has one of the highest modifiable attributable risks for cortical cataract and would therefore be an ideal target for public health intervention. Quit smoking campaigns can be expanded to incorporate information about the excess cataract in the community associated with long-term smoking. Nonmodifiable risk factors such as age, gender, and long-term medication use have implications for the timely referral and treatment for those at higher risk of cataract. (+info)