PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Lens Cortex, Crystalline”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources
PubMed1989

Lesion and regeneration of the anterior and posterior lens capsule and cortex in rabbits Nd:YAG laser.

With a mode-locked Nd:YAG laser set at various energy levels, anterior and posterior capsular and cortical lesions were produced in the lens of rabbits. Biomicroscopic and Scheimpflug examinations showed the anterior lesion to be healing in a whitish scar that was restricted to the area of the original lesion. Histology and transmission electron microscopy (TEM) demonstrated the proliferation of epithelial cells that produced a new, continuous, basement membrane-like capsule. In the area of the lesion collagenous material, myofibroblast-like cells and macrophages were found. Laser-induced lesions in the posterior lens capsule and lens protein resulted in damage to the capsule and grey opacity of the lenticular proteins, which remained unchanged for 6 weeks. Neither inflammatory nor epithelial cells appeared within the locally damaged lens. Macrophages migrated from the vitreous into the lesion; they were observed either in intercellular clefts or within a lens fibre, almost completely taking up their cross section.

Animals↗
PubMed1989

Excimer laser ablation of the human lens at 308 nm with a fiber delivery system.

A 308 nm excimer laser has been used with a fiber delivery system to perform ablation of the human lens. Preliminary results demonstrate the system's ability to ablate lens nucleus and cortex selectively, preserving the anterior and posterior capsules. The total delivered energy necessary to ablate a human lens ranged from 35 to 63 joules. Laser tissue interaction and ablation rates were computed for the different components of the human lens (capsule, cortex, nucleus) for the operatively useful energy densities (fluences). Operative experience suggests that cortex and nucleus can be ablated while preserving the capsule if an adequate irrigation and aspiration system is developed. These results also suggest that this modality may be adequate for performing endocapsular cataract extraction. Laser tissue interactions were also computed at variable distances between the fiber tip and tissue. As this distance increased, the spread of the beam increased and a significant increase in energy was necessary to induce tissue ablation. This was due to the decrease in fluence with increasing distance to the target tissue and/or the absorption and scattering of the delivered energy within a short distance from the fiber tip by the ablated material. Evidence of a sonic effect was also present.

Aged↗
PubMed1988

Lens Opacities Classification System.

The Lens Opacities Classification System (LOCS) is a simple system for classifying age-related human lens opacities at the slit lamp or in retroilluminated and slit-lamp photographs. The system employs a set of standard Neitz CTR retroilluminated black-and-white photographs for classification of cortical and posterior subcapsular cataracts and a single color slit-lamp photograph for classification of nuclear color and opalescence. We present a detailed description of the system.

Cataract↗
PubMed1989

Cigarette smoking and risk of nuclear cataracts.

The current study was undertaken to assess the relationship of smoking to the risk of lens opacities. The risk was evaluated separately for nuclear and cortical opacities and for both types together. We studied 838 watermen in Maryland by detailed ocular examination for the presence and severity of each cataract type. All subjects were interviewed regarding smoking history, and a cumulative smoking dose was calculated. The results suggest a significantly increased risk of pure nuclear opacities associated with cigarette smoking. The increase in smoking dose was associated with increasing severity of nuclear opacity. The risk of nuclear opacities increased with increasing cigarette dose and decreased if the subject had quit smoking. The effect of smoking was most striking in those less than 80 years old. No increased risk of nuclear opacities was observed with earlier age when smoking started, after adjusting for dose and cessation of smoking. Further investigations are warranted on the biochemical and physical damage to the nucleus of the lens from smoking cigarettes.

Adult↗
PubMed1992

The effect of early cataracts on glare and contrast sensitivity. A pilot study.

To establish the effect of cataracts on glare and contrast sensitivity, we graded type and amount of lens opacity in 110 subjects who underwent two glare tests (Brightness Acuity Tester and Berkeley glare test) and two contrast sensitivity tests (a sine-wave test and Pelli-Robson chart). Twenty-seven subjects (25%) had clear lenses (mean visual acuity of 20/20) and 83 subjects (75%) had early lens opacities (mean visual acuity of 20/40) in otherwise normal eyes. Multiple regression techniques were used to control for the effects of age and visual acuity. Glare test scores were significantly lower for nearly all patients with lens opacities than for patients with clear lenses and were the lowest for patients with lenses with posterior subcapsular opacity. Contrast sensitivity scores were lower for all patients with lens opacities than for patients with clear lenses at high frequencies only; all lens opacity groups scores similarly with each other. These results indicate reduced visual function among patients with cataracts whose visual acuity is only minimally impaired.

Cataract↗
PubMed1994

Supramolecular order within the lens: 1H NMR spectroscopic evidence for specific crystallin-crystallin interactions.

alpha-, beta- and gamma-crystallins from bovine lens contain flexible terminal extensions which are readily observed by NMR spectroscopy. By monitoring these resonances, NMR spectroscopy therefore offers a means of examining specific protein-protein interactions in crystallin mixtures. In this paper, a 1H NMR spectroscopic study of bovine lens nuclear and cortical homogenates and various crystallin mixtures is presented. In both homogenates, resonances from the flexible C-terminal extensions of alpha-crystallin and the N-terminal extension of beta B2-crystallin are readily observed suggesting that these regions are not involved in crystallin-crystallin interactions. In the cortical homogenate, resonances from the short N-terminal extension of gamma S-crystallin are also present. The cortical homogenate gives rise to more intense resonances than the nuclear homogenate, suggesting that the cortical region has many more mobile crystallin regions. In both homogenates, the C-terminal extension of beta B2-crystallin and the very short C-terminal extension of gamma B-crystallin are not observed. Thus, the C-terminal regions of these proteins are involved in interactions with other crystallins. Similar effects are observed upon mixing of the individual crystallins, e.g. the C-terminal extension of gamma B-crystallin is absent in spectra of mixtures of total gamma-crystallin and high-molecular-weight beta-crystallin aggregates (beta H). Overall, the results are consistent with a short-range order for the crystallins within the lens.

Animals↗
PubMed1983

Distribution of taurine in the crystalline lens of vertebrate species and in cataractogenesis.

Marked heterogeneity was observed in the distribution of taurine in different regions of the lens in various species. In general low taurine pools were observed in the nucleus of all species except frog and human. The distribution of taurine in human senile cataractous lenses at different stages of maturation showed decreased contents in all the regions except capsule epithelium as compared to the normal human lenses. This decrease is progressive upto the 'mature' stage of cataract. In rat lenses with galactose cataracts taurine contents decreased by about 83-94% of the normal values in the equatorial, anterior, posterior cortical and nuclear regions.

Animals↗
PubMed1984

Measurement of refractive index in an intact crystalline lens.

A knowledge of the refractive index distribution within the crystalline lens is necessary to define the optical properties of the eye. This report describes the first nondestructive method for measuring the refractive index of intact crystalline lenses based on the work of Chu (1977) [Electron Lett. 13, 736-738] and Barrell and Pask (1978) [Opt. Commun. 27, 230-234] for optical fibre preforms. The method is simpler and more accurate than previous methods and shows that the rat crystalline lens has a smooth and almost parabolic distribution of refractive index.

Animals↗
PubMed2006

Effect of cortical cleaving hydrodissection on posterior capsule opacification in age-related nuclear cataract.

PURPOSE: To evaluate the effect of multiquadrant cortical cleaving hydrodissection on the development of posterior capsule opacification (PCO) after phacoemulsification. SETTING: Iladevi Cataract and IOL Research Center, Ahmedabad, India. METHODS: A prospective randomized triple blind clinical trial was conducted in 86 eyes (86 patients) having phacoemulsification. Eyes were assigned randomly to Group 1, multiquadrant cortical cleaving hydrodissection and hydrodelineation (n = 48 eyes), or Group 2, no multiquadrant cortical cleaving hydrodissection, only hydrodelineation (n = 38 eyes). Age-related nuclear sclerosis (grading system of 1 to 5) and age greater than 50 years were included. Diabetes mellitus and associated eye diseases were excluded. Standard phacoemulsification with implantation of an AcrySof MA30BA intraocular lens (IOL) was done in both groups. High-resolution digital retroillumination images of the posterior capsule were analyzed at 4 years using POCOman software. Seven patients dropped out (8.1%). Outcome measures were incidence and percentage area of PCO. Test of proportions, independent sample t test, and 95% confidence intervals (CIs) were noted. RESULTS: In Groups 1 and 2, the mean age was 58 years +/- 4 (SD) and 57 +/- 5 years, respectively (P = .702; 95% CI, 1.90-2.81); mean follow-up was 48.4 +/- 2.5 months and 49.3 +/- 1.9 months, respectively (P = .687; 95% CI, 1.186-0.7856); incidence of PCO was 11 of 44 (25%) and 12 of 35 (34.3%), respectively (P = .317; 95% CI, 0.359-0.0889); percentage area of PCO was 14.3% and 25.6%, respectively (P = .006; 95% CI, -19.19 to -3.44). One of 44 eyes (2.27%) and 2 of 35 eyes (5.7%) in the groups, respectively, had a neodymium:YAG capsulotomy. CONCLUSION: Although no difference was noted in the incidence of PCO, in eyes that had PCO, the percentage of the area of the central posterior capsule involved by PCO was significantly lower in eyes that had multiquadrant cortical cleaving hydrodissection than in those that did not.

Aging↗
PubMed2000

Iris color and cataract: the Blue Mountains Eye Study.

PURPOSE: To investigate the relationship between eye color and cataract. METHODS: A population-based cross-sectional study (N = 3654) was conducted near Sydney, Australia. Lens photographs were graded for cortical, nuclear, and posterior subcapsular cataract. Iris color was assessed at slit-lamp examination by comparison with four photographic standards. RESULTS: Eyes with dark brown irises were more likely to have nuclear (adjusted odds ratio, 1.59; 95% confidence interval [CI], 1.03 to 2.28) or posterior subcapsular cataract (adjusted odds ratio, 2.50; 95% CI, 1.57 to 3.98) than eyes with lighter-colored irises. CONCLUSIONS: People with dark brown eyes are at increased risk of cataract and should be encouraged to protect their eyes from direct exposure to sunlight.

Cataract↗
PubMed1983

A simple method of implantation within the capsular bag.

We describe a new method of implantation in the capsular bag. The initial anterior capsulotomy incision is limited to a linear opening from 10 o'clock to 2 o'clock. The nucleus is expressed and the cortical remnants are removed. An implant, specially designed for this technique, is introduced vertically between anterior and posterior capsules and then rotated to a horizontal position entirely within the capsular bag. Finally, a central piece of anterior capsule is excised.

Cataract Extraction↗
PubMed1998

A longitudinal study of body mass index and lens opacities. The Framingham Studies.

OBJECTIVE: The purpose of the study was to determine whether body mass index (BMI) is an independent risk factor for the development of nuclear, cortical, or posterior subcapsular lens opacities. DESIGN: A cohort study. PARTICIPANTS AND METHODS: Eye examinations were conducted on surviving members of the Framingham Heart Study Cohort from 1973 to 1975 (Framingham Eye Study I) and again from 1986 to 1989 (Framingham Eye Study II). Data from the Framingham Heart Study, including weight measurements collected biennially from 1948, were used to examine associations between BMI (mean BMI across examinations, slope of BMI over time, and fluctuations in BMI) and the development of lens opacities. This analysis included 714 individuals, aged 52-80 years, who were free of lens opacities at the first eye examination. MAIN OUTCOME MEASURES: Development of nuclear, cortical, and posterior subcapsular lens opacities. RESULTS: A total of 444 persons developed lens opacities during the approximately 13 years between eye examinations. In logistic regression analyses that controlled for age, sex, education, diabetes, and smoking, the risk of developing cortical opacity increased with higher BMI at the time of the first eye examination (P = 0.002). Risk of cortical opacities also increased, at a borderline level of significance, with higher average BMI (P = 0.09) across examinations and increasing BMI levels over time (P = 0.10). There was a strong association between increasing BMI over time and the development of posterior subcapsular lens opacities (P = 0.002). No associations were found for nuclear lens opacities. CONCLUSIONS: Although the mechanism explaining the association is unclear, these findings suggest that BMI, a potentially modifiable characteristic, is associated with the development of cortical and posterior subcapsular lens opacities.

Aged↗
PubMed1994

Stop and chop phacoemulsification.

We present a method for phacoemulsification within the capsular bag in which sculpting is performed to provide space for nuclear manipulation and then the posterior plate is cracked into two halves. The nuclear rim is chopped into bite-size pieces for removal using a modified lens hook that is buried in the nuclear periphery and pulled toward the center. The procedure begins as a routine nuclear cracking technique and then stops. It continues as a chop technique.

Cataract Extraction↗
PubMed1989

Continuous-tear capsulotomy and insertion of a silicone bag lens.

Opacification of the posterior capsule and lack of intraocular lens fixation have been recurring problems and have resulted in a gradual shift from sulcus-fixated silicone lenses to bag-fixated silicone lenses. Postoperative capsular contraction, however, can cause capsular tearing in the periphery and intraocular lens decentration. A new method of combining a small circular capsulotomy, cataract removal without anterior capsular rim tearing, and meticulous bag placement of the silicone lens seems to allow centering and secure fixation of the silicone lens.

Cataract Extraction↗
PubMed2002

A simplified cataract grading system.

A simplified method for grading the presence and severity of different cataract types is needed for field use in assessment of the magnitude of the cataract problem. A cataract grading system was developed by a panel of experts with the objective of making available a simple system for use with a slit lamp to allow for the reliable grading of the most common forms of cataract by relatively inexperienced observers. Three levels, reflecting progressive severity, for grading of nuclear, cortical and posterior subcapsular (PSC) cataract were included in the classification; three standard photos were used for grading nuclear cataract. Field evaluation from four different sites indicated very good to fair interobserver agreement with the use of this system following minimal training of residents in ophthalmology at each site. Further testing of this system is warranted. The WHO simplified cataract grading system should allow for the obtaining of comparable data across countries based on field assessment of the most common forms of cataract.

Cataract↗
PubMed1996

Contrast sensitivity in different types of early lens opacities.

The purpose of the present study was to evaluate the relationship of various types of early lens opacities with contrast sensitivity at different spatial frequencies. The Lens Opacities Classification System II and Lensmeter 701 were used in the grading of the lens status. The contrast sensitivity was tested with the Vistech VCTS 6500 distance test with optimal correction of refractive errors. Data from 995 eyes were available for the present study. Contrast sensitivity decreased by increasing lens opacification graded with the Lens Opacities Classification System II and also by increasing Lensmeter 701 reading. When the statistical model was adjusted for age and best corrected visual acuity, nuclear opacities and nuclear colour were not associated with decreased contrast sensitivity, however, there was a weak, but statistically significant correlation between contrast sensitivity reduction and cortical opacities at high spatial frequencies, and between contrast sensitivity and posterior subcapsular opacities at low and medium spatial frequencies.

Adult↗
PubMed2005

A case-control study on risk factors for nuclear, cortical and posterior subcapsular cataract: The Casteldaccia Eye Study.

PURPOSE: To investigate risk factors for nuclear, cortical and posterior subcapsular age-related cataract. METHODS: A case-control study was carried out on subjects aged 40 years and older, living in Casteldaccia, Sicily. Twenty-seven potential risk factors were investigated. Nuclear, cortical and posterior subcapsular opacities of the lens were classified according to the Lens Opacities Classification System II. Subjects with advanced lens opacities represented the cases, while an identical number of subjects without or with early cataract, matched for sex and age, were recruited as controls from within the same population. RESULTS: Univariate analysis showed that myopia and iris atrophy were significantly associated with nuclear cataract. Iris atrophy, use of corticosteroids, pseudoexfoliation syndrome and familial occurrence of cataract were positively correlated with cortical cataract. Myopia, iris atrophy, use of corticosteroids and familial occurrence of cataract presented an association with posterior subcapsular cataract. After multivariate analysis, the variables that remained significantly associated were myopia and iris atrophy for nuclear cataract; iris atrophy, pseudoexfoliation syndrome and familial occurrence of cataract for cortical cataract; and myopia, iris atrophy and familial occurrence of cataract for posterior subcapsular cataract. CONCLUSION: In addition to well known risk factors such as myopia or use of corticosteroids, the Casteldaccia case-control study shows that iris atrophy represents a previously unrecognized risk factor for each of the three types of cataract.

Adult↗