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Publications (7)34.17 Total impact

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    ABSTRACT: To determine the prevalence of age-related macular degeneration (AMD) and to identify its risk factors in an Oklahoma Indian population. Cross-sectional study design. Included 1019 Oklahoma Indians who participated in baseline and second examinations of the Strong Heart Study. Retinal photographs of at least 1 eye were obtained and graded for AMD by the University of Wisconsin Ocular Epidemiology Reading Center. Retinal photographs of 986 participants were considered gradable and were included in the study. Age-related macular degeneration (early and late). The overall prevalence of AMD in the study was 35.2%, including a prevalence of 0.81% for late AMD. The prevalence of early AMD increased from 30.6% in those aged 48 to 59 years to 46.1% in those 70 to 82 years of age. When potential risk factors were analyzed individually (univariate analyses), men with hypertension had a significantly higher prevalence of AMD (P = 0.02) than those without hypertension. In women, high-density lipoprotein cholesterol and sun exposure were associated positively with the prevalence of AMD (P = 0.01), whereas a history of using multivitamins was associated with lower AMD prevalence (P = 0.005). When multiple risk factors were analyzed simultaneously using logistic regression, only age showed significant association with AMD in both men (P = 0.02) and women (P<0.0001) and was the only significant risk factor in men. In women, multivitamin use and total cholesterol had a significant inverse association with AMD, whereas sun exposure and high-density lipoprotein cholesterol had a positive association. When men and women were combined, age and high-density lipoprotein cholesterol had significant positive associations, whereas total cholesterol, multivitamin use, and current alcohol use showed a significant inverse association with AMD. This study was the first to report a detailed prevalence of AMD in Oklahoma Indians and its risk factors. The prevalence seemed to be relatively high compared with that in other ethnic groups. Some of the modifiable risk factors identified confirmed previous findings and can be used to design preventive programs to reduce the burden of AMD, although longitudinal data are still needed.
    Ophthalmology 01/2011; 118(7):1380-1385. · 5.56 Impact Factor
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    ABSTRACT: To identify and characterize biochemical alterations in the retinas of very low-density lipoprotein receptor (VLDLr) knockout mice in an animal model of retinal angiomatous proliferation. Immunohistochemical analysis, Western blot analysis, reverse transcriptase-polymerase chain reaction, and electrophoretic mobility shift assay were used to identify and characterize the altered gene and protein expression as well as signal cascades involved in the pathogenesis of neovascularization in the retinas of VLDLr mice. Expression of the angiogenic factors vascular endothelial growth factor and basic fibroblast growth factor was significantly greater in the lesion area, and Müller cells around the lesion area were activated, as indicated by increased expression of glial fibrillary acidic protein. Expression of the proinflammatory cytokine IL-18 (interleukin 18) and the inflammation mediator intercellular adhesion molecule-1 was increased before significant intraretinal neovascularization. Furthermore, phosphorylation of Akt and mitogen-activated protein kinase and translocalization of nuclear factor kappa B were greater in VLDLr knockout mouse retinas. An inflammatory process is involved in the development of neovascularization in the VLDLr knockout mouse retina. Understanding the molecular mechanisms underlying these biochemical alterations in the retinas of VLDLr knockout mice will provide a foundation for developing novel therapeutic approaches to retinal angiomatous proliferation.
    Archives of Ophthalmology 07/2007; 125(6):795-803. · 3.83 Impact Factor
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    ABSTRACT: To determine the prevalence of visual impairment and eye abnormalities in Oklahoma Indians. The cross-sectional study included 1019 Oklahoma Indians, aged 48 to 82 years; 60.2% were women. All participants gave a personal interview, and all underwent an eye examination, including the determination of best-corrected visual acuity and an ophthalmoscopic examination. In addition, two 45 degrees fundus photographs were taken of each eye, and these photographs were graded by the Fundus Photography Reading Center at the University of Wisconsin, Madison. Among the 1019 participants, 77.4% had a visual acuity of 20/20 or better, 19.5% and 2.5% had visual acuities of between 20/25 and 20/40 and between 20/50 and 20/190, respectively; and 0.6% were legally blind, all in the better eye. Cataract was the most frequent contributing cause and age-related macular degeneration the second most frequent contributing cause of visual impairment. The overall prevalence proportions of age-related macular degeneration, cataract, diabetic retinopathy, and definite glaucoma were 33.6%, 39.6%, 20.1%, and 5.6%, respectively. Most of the other eye abnormalities were rare in the study participants, except for pinguecula (42.4%) and dermatochalasis (30.1%). Oklahoma Indians have a higher prevalence of visual impairment, age-related macular degeneration, and diabetic retinopathy than other ethnic groups. The implementation of adequate treatment and prevention programs for eye diseases is indicated.
    Archives of Ophthalmology 01/2006; 123(12):1699-704. · 3.83 Impact Factor
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    ABSTRACT: To propose methods for computer grading of the severity of 3 early lesions, namely, hemorrhages and microaneurysms, hard exudates, and cotton-wool spots, and classification of nonproliferative diabetic retinopathy (NPDR) based on these 3 types of lesions. Using a computer diagnostic system developed earlier, the number of each of the 3 early lesions and the size of each lesion in the standard photographs were determined. Computer classification criteria were developed for the levels of individual lesions and for NPDR. Evaluation of the criteria was performed using 430 fundus images with normal retinas or any degree of retinopathy and 361 fundus images with no retinopathy or the 3 early lesions only. The results were compared with those of the graders at the University of Wisconsin Ocular Epidemiology Reading Center and an ophthalmologist. Agreement rates in the classification of NPDR between the computer system and human experts. In determining the severity levels of individual lesions, the agreement rates between the computer system and the reading center were 82.6%, 82.6%, and 88.3% using the 430 images and 85.3%, 87.5%, and 93.1% using the 361 images, respectively, for hemorrhages and microaneurysms, hard exudates, and cotton-wool spots. When the "questionable" category was excluded, the corresponding agreement rates were 86.5%, 92.3%, and 91.0% using the 430 images and 89.7%, 96.3%, and 97.4% using the 361 images. In classifying NPDR, the agreement rates between the computer system and the ophthalmologist were 81.7% using the 430 images and 83.5% using the 361 images. The proposed criteria for computer classification produced results that are comparable with those provided by human experts. With additional research, this computer system could become a useful clinical aid to physicians and a tool for screening, diagnosing, and classifying NPDR.
    Archives of Ophthalmology 07/2005; 123(6):759-64. · 3.83 Impact Factor
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    ABSTRACT: To investigate whether a computer vision system is comparable with humans in detecting early retinal lesions of diabetic retinopathy using color fundus photographs. A computer system has been developed using image processing and pattern recognition techniques to detect early lesions of diabetic retinopathy (hemorrhages and microaneurysms, hard exudates, and cotton-wool spots). Color fundus photographs obtained from American Indians in Oklahoma were used in developing and testing the system. A set of 369 color fundus slides were used to train the computer system using 3 diagnostic categories: lesions present, questionable, or absent (Y/Q/N). A different set of 428 slides were used to test and evaluate the system, and its diagnostic results were compared with those of 2 human experts-the grader at the University of Wisconsin Fundus Photograph Reading Center (Madison) and a general ophthalmologist. The experiments included comparisons using 3 (Y/Q/N) and 2 diagnostic categories (Y/N) (questionable cases excluded in the latter). In the training phase, the agreement rates, sensitivity, and specificity in detecting the 3 lesions between the retinal specialist and the computer system were all above 90%. The kappa statistics were high (0.75-0.97), indicating excellent agreement between the specialist and the computer system. In the testing phase, the results obtained between the computer system and human experts were consistent with those of the training phase, and they were comparable with those between the human experts. The performance of the computer vision system in diagnosing early retinal lesions was comparable with that of human experts. Therefore, this mobile, electronically easily accessible, and noninvasive computer system, could become a mass screening tool and a clinical aid in diagnosing early lesions of diabetic retinopathy.
    Archives of Ophthalmology 05/2001; 119(4):509-15. · 3.83 Impact Factor
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    ABSTRACT: To compare fundus photography with ophthalmoscopy in the detection of diabetic retinopathy. Ophthalmoscopy and fundus photographs with a nonmydriatic camera, both performed through dilated pupils, were compared to diagnose retinopathy in a cohort of 410 Oklahoma Indians with noninsulin-dependent diabetes mellitus. A total of 795 eyes were examined using both methods. The mean age of participants was 60.3 years, with a mean duration of diabetes of 17.3 years. An overall agreement of 86.3% with a kappa statistic kappa of 0.74 was found between ophthalmoscopy and fundus photography with a nonmydriatic camera. For the diagnosis of proliferative diabetic retinopathy, kappa = 0.84 with an agreement of 98.1%. With a total of 61 cases of proliferative retinopathy diagnosed by either method in our study, ophthalmoscopy alone detected 88.5% and fundus photography, 78.7%. When compared on a lesion-by-lesion basis, agreement between the two diagnostic methods was highest for nonproliferative retinopathy, as well as fibrous proliferation. The fundus photography with a nonmydriatic camera, performed with mydriasis, is comparable to ophthalmoscopy for the detection of retinopathy. It may prove to be a suitable, cost-effective method for routine screening in diabetes clinics, provided ophthalmologic referral is ensured for those with a diagnosis of any form of retinopathy, questionable retinopathy, nondiabetic retinopathy, those with poor quality photographs, as well as those with acute changes in visual acuity.
    Ophthalmology 11/1993; 100(10):1504-12. · 5.56 Impact Factor
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    ABSTRACT: To determine the incidence rates and risk factors for development of diabetic retinopathy in Oklahoma Indians. Cohort follow-up study with baseline examination between 1972 and 1980 and follow-up examination between 1987 and 1991. Mean +/- SD follow-up time was 12.8 +/- 1.7 yr. Eleven Indian Health Service facilities (clinics and hospitals) in Oklahoma participated in the study. Study participants were a quasirandom sample of 1012 American Indians (379 men, 633 women) in Oklahoma with NIDDM, 927 of whom received a detailed eye examination at baseline. The mean age of participants was 52 yr with a duration of diabetes of 6.9 yr at baseline. The average quantum of Indian blood was 92% (77% full blood). At follow-up, 515 (55.6%) were alive, 408 (44.0%) were deceased, and 4 (0.4%) could not be traced. Of the living participants, 380 (73.8%) underwent an ophthalmoscopic examination. The incidence of retinopathy among the participants who were free of disease at baseline and who survived the follow-up interval was 72.3%. By multivariate analysis, significant independent predictors of retinopathy recorded at baseline were FPG level, therapeutic regimen, systolic blood pressure, and duration of diabetes. FPG levels > or = 11.1 mM (200 mg/dl) increased the risk of retinopathy 1.7 times that for levels < 7.8 mM (140 mg/dl). Insulin use was associated with a 20% greater incidence. Hypertension was a particularly significant risk factor for those with lower FPG levels. Given that NIDDM is reaching epidemic proportions in Oklahoma Indians and that most may be afflicted with retinopathy, frequent ophthalmological examinations are clearly indicated for this high-risk population. The role of intervention, namely glycemic and hypertensive control, deserves further study.
    Diabetes Care 12/1992; 15(11):1620-7. · 7.74 Impact Factor