Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0086543 (cataract)
 29,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Linkage data relative to the markers tabby and glucose-6-phosphate dehydrogenase are presented to locate X-linked cataract (Xcat) in the distal portion of the mouse X-chromosome between jimpy and hypophosphatemia. The human X-linked cataract-dental syndrome, Nance-Horan Syndrome, also maps closely to human hypophosphatemia and would suggest homology between mouse Xcat and human Nance-Horan Syndrome genes. In hemizygous males and homozygous females penetrance is complete with only slight variation in the degree of expression. Phenotypic expression in Xcat heterozygous females ranges from totally clear to totally opaque lenses. The phenotypic expression between the two lenses of a heterozygous individual could also vary between totally clear and totally opaque lenses. However, a correlation in the degree of expression between the eyes of an individual was observed. A variegated pattern of lens opacity was evident in female heterozygotes. Based on these observations, the site of gene action for the Xcat locus is suggested to be endogenous to the lens cells and the precursor cell population of the lens is concluded to be small. The identification of an X-linked cataract locus is an important contribution to the estimate of the number of mutable loci resulting in cataract, an estimate required so that dominant cataract mutagenesis results may be expressed on a per locus basis. The Xcat mutation may be a useful marker for a distal region of the mouse X-chromosome which is relatively sparsely marked and the X-linked cataract mutation may be employed in gene expression and lens development studies.
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PMID:Genetic localization and phenotypic expression of X-linked cataract (Xcat) in Mus musculus. 227 5

The Lens Opacity Meter (LOM) has been developed as a method of quantifying lens opacity. It was compared both with a photographic system and with measured visual acuity. The LOM is a simple system to operate and requires minimal training. LOM readings were correlated with the presence and severity of nuclear opacity and also total cataract grade. It also showed a correlation with visual acuity. LOM readings were not useful in documenting the presence or severity of cortical or posterior subcapsular opacity, and in these cases there was considerable variation in the LOM readings. These data suggest that the LOM may be of limited value as a simple screening test, but it has limited use in discriminating between various types of severity of opacities.
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PMID:The lens opacity meter: a method of quantification of lens opacity by measurement of scattering of incident light. 227 24

The administration of high dosages of various hydroxymethylglutaryl-CoA (HMG-CoA) reductase inhibitors has resulted in the development of subcapsular lenticular opacities in dogs. While dogs receiving cataractogenic doses of HMG-CoA reductase inhibitors experienced profound decreases in circulating serum cholesterol concentrations (40-60% reductions in total serum cholesterol), a causal relationship between serum cholesterol lowering and cataractogenesis was not established. A strong relationship was demonstrated, however, between the systemic exposure to inhibitor (plasma drug levels) and the cataractogenic potential of the various compounds studied. Analysis of lenses from dogs chronically dosed with various HMG-CoA reductase inhibitors revealed the presence of low drug levels in the lens (less than 500 ng equivalents g-1), but no correlation was observed between the amount of drug associated with the lens after chronic treatment and cataract development. In addition, no abnormalities in cholesterol content or sterol composition were observed in clear and/or cataract containing lenses from dogs chronically dosed with HMG-CoA reductase inhibitors. The kinetics of drug appearance in the aqueous and lens cortex was assessed after doses of various HMG-CoA reductase inhibitors, and suggested somewhat higher but not statistically significant peak concentrations of inhibitor were achieved by compounds which produced a higher incidence of cataracts. These data have suggested that high doses of HMG-CoA reductase inhibitors may increase lenticular exposure to drug via the aqueous humor by producing a substantial systemic exposure to drug substance. This may result in an increased concentration of inhibitor in the outer cortical region of the lens where cholesterol synthesis is critical, thereby resulting in the development of opacities. The production of lenticular changes by a HMG-CoA reductase inhibitor of diverse chemical structure establishes, with reasonable assurance, that these lens changes are mechanism based (i.e. a product of the biochemical mechanism of action of this class of compounds). An extrapolation of these findings to patients receiving therapeutic dosages enables a favorable risk evaluation since the doses to be employed clinically are much lower and result in a far lower systemic exposure to drug substance.
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PMID:On the etiology of subcapsular lenticular opacities produced in dogs receiving HMG-CoA reductase inhibitors. 230 97

The quantitative influence of cataracts on visual fields was studied in 11 patients before and after cataract extraction with intraocular lens implantation. Lens opacity, measured with the Opacity Lens Meter 701, correlated closely with the visual field changes. Measurement of stray light backscattered from the cataractous lens permits quantitative prediction of the influence of cataract on the visual field.
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PMID:[The Opacity Lens Meter 701: clinical experiences]. 236 62

The Lens Opacities Classification System I (LOCS I) was used to classify lens opacities in the clinic-based Italian-American Case-Control Study of Age-Related Cataract. Data on the distribution of cataract types among the 1008 patients (age range, 45-79 years) are presented. A single type of cataract was found in 65% of all cases in whom both lenses could be graded. Among all patients and among patients with only one type of cataract, cortical opacities occurred most frequently and posterior subcapsular opacities least frequently. In patients with bilateral cataracts there was a high degree of concordance of cataract type and severity. The high degree of concordance of cataract type between eyes and the decreasing prevalence of unilateral cataract with increasing age suggest that patients with unilateral cataract are at high risk of developing the same opacity in the fellow eye. Cortical cataracts were found more frequently in women, and in patients with unilateral cataract, the left eye was more frequently affected. Clinic-based data on the distribution of cataract may be of assistance in planning future clinical studies of cataract.
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PMID:Distribution of lens opacities in the Italian-American Case-Control Study of Age-Related Cataract. The Italian-American Study Group. 237 79

The frequency of complications after surgical iridectomy in angle-closure glaucoma is normally considered low. In order to estimate the influence of the surgical intervention independent from other factors (such as ischemia caused by angle-closure, progression of glaucomatous disease, medical treatment), 35 eyes that had undergone a prophylactic iridectomy because of acute angle closure of the contralateral eye were investigated retrospectively. The mean follow-up time of the 35 eyes was 6.1 years. None of the prophylactically iridectomized eyes developed angle-closure during follow-up. No significant change in visual acuity was present in the group of patients less than 65 years of age (n = 12). This group had a preoperative visual acuity of 0.85 +/- 0.18 and a visual acuity of 0.81 +/- 0.20 at the last visit. A considerable decrease in visual acuity, however, was found in the group of patients more than 65 years of age (n = 23). This group had a preoperative visual acuity of 0.64 +/- 0.24 and a visual acuity of 0.36 +/- 0.23 at the last visit. Biomicroscopically, one eye (8%) in the age group less than 65 years developed further lens opacity, whereas 15 eyes (65%) in the age group more than 65 years developed further lens opacity. In 2 eyes in the older group a cataract operation was performed. Five eyes developed posterior synechiae; in all of these eyes cataract formation increased. The results indicate that cataract progresses more rapidly after iridectomy if the patients are older.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Long-term results following preventive iridectomy. A retrospective study]. 237 74

We performed an epidemiological study to identify risk factors of cataract based on 2,243 subjects who underwent a general health checkup. Each subject underwent a 75-gram oral glucose tolerance test and blood chemistry analysis. The prevalence rate of cataract was higher in diabetic subjects in their 50s than in nondiabetics in the same age range (p less than 0.01). The incidence of vesicular and radial lens opacity was higher in diabetics than in nondiabetics (p less than 0.05).
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PMID:Diabetes as risk factor of cataract: differentiation by retroillumination photography and image analysis. 238 57

Lens opacity was quantified in 85 cataractous patients, using a new instrument: the lens opacity meter 701 (LOM; Interzeag, Schlieren, Switzerland). Cataracts were classified as nuclear, cortical, subcapsular and mixed forms. Sensitivity, specificity and reproducibility of the results were evaluated by statistical analysis. Visual acuity was correlated with LOM values in patients with nuclear and mixed cataracts. Moreover, the instrument gave a good degree of reproducibility only in patients who presented these forms of lens opacities. Our findings demonstrate that the LOM 701 is able to detect and to measure only lens opacities which affect the central area of the lens.
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PMID:Quantification and measurement of human lens opacities using the lens opacity meter. 239 78

The Lens Opacity Meter 701 (Interzeag, Switzerland) is a recently developed instrument for assessing cataract. It measures the degree of scatter of a red light beam by the lens. Fifty patients prior to cataract surgery had measurements made before and after dilatation of the pupil. Inconsistent results were found at pupil diameters of less than 4 mm. It is postulated that this was due to absorption of scattered light by the iris.
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PMID:Influence of pupil size on measurements made with the Lens Opacity Meter 701. 239 43

The Lens Opacities Classification System (LOCS II) has been tested as a method for detecting and grading longitudinal changes in cataract severity. The LOCS I and II systems have already been tested and validated for cross-sectional classification of human cataracts in vivo. 130 eyes (of 68 patients) were photographed at baseline and follow-up visits with Neitz CTR and Zeiss slit photography. The mean length of follow-up was 14.7 +/- 4.4 months. The severity of nuclear opalescence (NO), cortical (C) and posterior subcapular cataract (P) was graded in a masked fashion using the LOCS II standards. Side-by-side comparisons of baseline and follow-up photos were also done in a masked fashion to detect more subtle changes than might be evident in the LOCS II gradings. The annual percent progression in cataracts graded by LOCS II standards are: (NO): 12.4%, (C): 17.9%, and (P): 6.5%. The LOCS II standards are offered as a promising subjective method for longitudinal grading of human cataractous change in vivo.
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PMID:Strategies for measuring the rate of age-related cataract formation in vivo. 248 69


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