ISSN:1040-5488    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Blindness due to cataract continues to take a heavy toll on economic, social, and personal resources. Research into factors that may cause or prevent cataracts is of the highest priority. In this paper, the epidemiological evidence is summarized on the role of sunlight exposure and antioxidants for cataract. To date, there are consistent findings linking ultraviolet B (UV-B) radiation to cataract, particularly cortical and posterior subcapsular opacities. Antioxidants are likely to exert a protective effect against oxidative stress in the lens, but the current epidemiologic data present less coherent support for this hypothesis. Difficulties in summarizing these data include different methods for assessing antioxidant status, widely varying populations, and different research designs. Nevertheless, most studies have found some measure of antioxidant status to be associated with some type of cataract. Future research directions are described.

ISSN:1040-5488    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

A phase separation inhibitor, WR77913 [S-3(amino-2-hydroxypropyl) phosphorothioate], was tested for its effects on lens opacification in the radiation (RAD), selenite (SEL), galactose (GAL), streptozotocin (STZ), and Royal College of Surgeons (RCS) models for cataract. A single i.p. injection of WR77913, approximately 15 min before induction of cataract formation by RAD, SEL, STZ delayed or inhibited opacification. Repeated administration was necessary to delay or inhibit opacification in the GAL or RCS models for cataracts. The results suggest that phase separation inhibitors such as WR77913 have the potential to delay or inhibit lens opacification resulting from a variety of physiological or biochemical mechanisms.

ISSN:1040-5488    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

The subjective classification of lens opacities is a fundamental component in both the clinical evaluation of the individual patient and in large-scale clinical trials. This procedure has been improved substantially by the implementation of standardized photographic systems depicting various levels of nuclear opacity and color, cortical, and posterior-subcapsular cataract. Comparison can also be made with recently developed objective measurements of opacity and color. Further improvements in reliability and sensitivity to change can be achieved by modifying traditional integer scaling systems by interpolating between photographic standards.

ISSN:1040-5488    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Subjective and objective systems are used to quantify cataract at The Center for Clinical Cataract Research. We have described each system and its use, presented data on reproducibility and validity, and for objective systems, demonstrated the correlation to the subjective grade of the cataract as defined by the Lens Opacities Classification Systems, Versions II and III (LOCS II and III). The subjective systems are used to classify nuclear color, nuclear opalescence, cortical cataract, and posterior subcapsular cataract. Reportedkappascores for LOCS II range from 0.85 to 1.0. Intra-class correlation coefficients for LOCS III (n) range from 0.67 to 0.94. The computerized objective systems are: (1) fast spectral scanning colorimetry (FSSC) for assessment of nuclear color (n = 0.96 to 0.98); (2) nuclear mean density (NMD) for assessment of nuclear opalescence (r, = 0.97); and (3) percent area opacity (anterior = a; posterior = p) (OPAC-a and OPAC-p) for assessment of cortical and posterior subcapsular cataract (r, = 0.92 to 0.96).

ISSN:1040-5488    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

This paper reviews recent research on the evaluation of visual function in cataract. Visual impairment in cataract is principally caused by increased intraocular forward light scatter. It is assumed that visual acuity (VA) measurements assess the impact of narrow angle light scatter. This also makes the measurement of high spatial frequency contrast sensitivity (CS) unnecessary. However, VA measurements alone are an inadequate assessment of visual impairment in some patients with cataract. In addition, it is suggested that a measurement of wide-angle light scatter is required. This can be evaluated directly using the van den Berg Straylightmeter, or indirectly using low spatial frequency CS or disability glare (DG) tests. The following are discussed: (1) the relative usefulness of these tests; (2) how they can be incorporated into the decision as to when to extract a cataract; and (3) the importance of considering binocular visual function.

ISSN:1040-5488    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

The clinician involved in cataract assessment is often faced with a deterioration in visual performance which may or may not be totally attributable to the cataract. Neural changes may occur concurrently and contribute toward the reduced performance. This paper reviews the methods which attempt to discriminate between changes due to cataract development and changes produced by neural degeneration. New techniques have been developed with more emphasis on quantitative rather than qualitative assessment. These techniques are discussed critically with particular reference to their ability to distinguish between the contributions of optical and neural change. This has particular application in predicting the visual outcome after cataract surgery.

ISSN:1040-5488    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

The detectability of a signal decreases in the presence of externally added visual noise. A linear relation exists between the energy of a signal at threshold and the spectral density of the added visual noise. This relation, represented by contrast detection in noise function, allows a given loss in contrast sensitivity (CS) to be attributed to an increase in the internal intrinsic noise and/or a decrease in the detection efficiency of the observer. Intrinsic noise gives a measure of the random background noise within the visual system, whereas detection efficiency is a measure of how effectively the observer utilizes the available stimulus information. Recent work shows that neural dysfunction produces a decrease in the detection efficiency, whereas optical deficits produce a change in the intrinsic noise only. We investigated whether the CS loss in cataract can be attributed to either a change in intrinsic noise, in detection efficiency, or both. Contrast detection in noise functions was measured for 10 uniocular cataract patients. Comparison between the two eyes showed no significant difference in detection efficiency, although the intrinsic noise increased significantly in the cataractous eye. The data suggest that detection efficiency may provide a measure of neural visual function behind a cataract and, conversely, that intrinsic noise provides a measure of the visual effect of the cataract itself. We discuss the implications of intrinsic noise as a measure of cataract for both clinical assessment and research.

ISSN:1040-5488    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

The Lens Opacities Classification Systems (LOCS III) was developed and standardized using photograding. The purpose of this study was to assess the validity of LOCS III at the slitlamp and to compare slitlamp with photograding. To do so, two independent observers graded cataract at the slitlamp and in photographs from two sets of patients; the first set consisted of 205 eyes (193 acceptable photographs) and the second set of 51 eyes (51 photographs). The 95% tolerance limits (TL) for grading at the slitlamp ranged from 0.9 to 1.8 for the first set and 0.6 to 1.2 for the second (intraclass correlation coefficients 0.79 to 0.91 vs. 0.70 to 0.97, respectively). Specifically, there was a significant decrease in 95% TL for cortical and nuclear color. For the first set of photograding, the 95% TL were 0.3 to 0.6 between the two observers and 0.6 to 0.8 for the same observer at two different sessions. Similar results were found for photograding the second set. The 95% TL for comparing slitlamp and photograding were generally < 1.0. The results suggest that (1) LOCS III at the slitlamp has 95% TL only slightly worse than those for LOCS III photogradings; (2) LOCS III slitlamp grading for cortical and nuclear color improves with practice; and (3) the slitlamp and photographic gradings cannot be used interchangeably.

ISSN:1040-5488    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

The crystallin profiles of the cortices and nuclei of intracapsular cataractous lenses were studied by high pressure liquid chromatography (HPLC), polyacryl-amide gel electrophoresis (PAGE), and dot blotting. The complete personal and medical history of 381 patients and the Cooperative Cataract Research Group (CCRG) classification of each were obtained. Few statistically significant associations between patient personal history and cataract types were found. Protein profiles of selected cataracts which had specifically located opacities (i.e., nuclear only, cortical only, etc.) were studied in detail. Sodium dodecyl sulphate-PAGE revealed few differences in lens-soluble proteins between cataractous and normal cortices or nuclei. By HPLC, the proteins of cataractous cortices and their nuclei differed very little from age-matched controls. The cortical proteins of nuclear cataracts appeared normal. However, two major alterations of proteins were observed in the nuclei of dense nuclear cataracts. Increased high molecular weight protein and increased components with molecular weights <20,000 Da were found in cataractous nuclei as compared with normal age-matched control lens nuclei. Dot blot (immunological) analyses identified the crystallins of normal lenses that eluted from the HPLC column more efficiently than those of cataractous lenses. Cortical protein HPLC samples had the most specificity. Nuclear protein HPLC samples of older normal and cataractous lenses had little if any alpha crystallin specificity in the void volume peak. A relation between the presence of opacities and changes in molecular weight distribution of crystallins was found in the opaque nuclei but not in the opaque cortices. Cortical opacities seem more related to structural changes in the fiber cells, whereas nuclear opacities may be related to altered states of the crystallins, such as aggregation and breakdown.

ISSN:1040-5488    

出版商:OVID    

年代:1993

数据来源: OVID