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L T Chylack

Publications and source records attributed to L T Chylack.

At least 55 records · Page 3Linked to original sources
PubMed1993

The Lens Opacities Classification System III. The Longitudinal Study of Cataract Study Group.

OBJECTIVE: To develop the Lens Opacities Classification System III (LOCS III) to overcome the limitations inherent in lens classification using LOCS II. These limitations include unequal intervals between standards, only one standard for color grading, use of integer grading, and wide 95% tolerance limits. DESIGN AND RESULTS: The LOCS III contains an expanded set of standards that were selected from the Longitudinal Study of Cataract slide library at the Center for Clinical Cataract Research, Boston, Mass. It consists of six slit-lamp images for grading nuclear color (NC) and nuclear opalescence (NO), five retroillumination images for grading cortical cataract (C), and five retroillumination images for grading posterior subcapsular (P) cataract. Cataract severity is graded on a decimal scale, and the standards have regularly spaced intervals on a decimal scale. The 95% tolerance limits are reduced from 2.0 for each class with LOCS II to 0.7 for nuclear opalescence, 0.7 for nuclear color, 0.5 for cortical cataract, and 1.0 for posterior subcapsular cataract with the LOCS III, with excellent interobserver agreement. CONCLUSION: The LOCS III is an improved LOCS system for grading slit-lamp and retroillumination images of age-related cataract.

Aging↗
PubMed1993

Contrast sensitivity and visual acuity in patients with early cataracts.

In a population of 188 nondiabetic patients with early cataracts or nuclear brunescence, we assessed the degree to which contrast sensitivity function (CSF) provided more information about a patient's visual disability than high contrast visual acuity measurements. Data collected included LOCS II cataract classification, Bailey-Lovie visual acuity (LogMAR score), Lotmar interferometric visual acuity (LI VA), and distance contrast sensitivity function (CSF) using the Vistech 6500. Generalized least squares regression models in which CS was the dependent variable and either LogMAR score or LI VA was among the independent variables were used to ascertain whether CSF provided additional information about visual disability to that provided by LogMAR score or LI VA. Contrast sensitivity function was decreased only by nuclear opalescence at high frequencies (12 to 18 cpd); for all other cataract types and nuclear color, CSF testing provided no more information about cataract-related visual loss than LI VA or LogMAR score. Measurement of CSF using the Vistech 6500 system in patients with early cataracts provides information on visual dysfunction beyond that provided by LogMAR score or LI VA only in patients with nuclear opalescence, and that may not be clinically significant.

Adult↗
PubMed1993

Quantitating cataract and nuclear brunescence, the Harvard and LOCS systems.

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. Reported kappa scores for LOCS II range from 0.85 to 1.0. Intraclass correlation coefficients for LOCS III (r1) range from 0.67 to 0.94. The computerized objective system are: (1) fast spectral scanning colorimetry (FSSC) for assessment of nuclear color (r1 = 0.96 to 0.98); (2) nuclear mean density (NMD) for assessment of nuclear opalescence (r1 = 0.97); and (3) percent area opacity (anterior = a; posterior = p) (OPAC-a and OPAC-p) for assessment of cortical and posterior subcapsular cataract (r1 = 0.92 to 0.96).

Adult↗
PubMed1993

Evaluation of lens opacities classification system III applied at the slitlamp.

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.

Adult↗
PubMed1993

Lovastatin and the human lens; results of a two year study. The MSDRL Study Group.

Lovastatin has been associated with development of subcapsular cataract in dogs given high doses. To test the cataractogenic potential of lovastatin in humans, 192 patients were divided into 2 groups, A (N = 94) and B (N = 98), 1 taking 40 mg/day of lovastatin and 1 taking placebo. Both groups were enrolled for 2 years in this double-blind, randomized study and were followed with eye examinations including assessment of visual function, Lens Opacities Classification System II (LOCS II) cataract and nuclear color classification, and computerized lens image analysis. There were no statistically significant differences in visual function between the two groups. Similarly, cataract progression, assessed by LOCS II measurement and by computerized measurements of cataract, showed no important differences between the treatment groups. These data show no cataractogenic effect of lovastatin in humans.

Cataract↗
PubMed1993

Objective line spread function measurements, Snellen acuity, and LOCS II classification in patients with cataract.

We tested an instrument to measure the line spread function (LSF) of the eye in order to assess objectively retinal image degradation due to cataract. Optical aberrations from 62 eyes with early to moderate cataract were assessed by measuring the extent of blurring of a best-focused fine line image (LSF) projected onto a subject's retina. The instrument consisted of a slitlamp equipped with a Hruby lens to project the line and a computer-coupled CCD camera to record and measure the blurred image. We hypothesized that the width of the blurred line image (called WSCAT) due to light scattering in the cataractous lens would be affected most by nuclear and subcapsular cataracts. The WSCAT results were compared to the data from two other tests: (1) Snellen acuity and (2) LOCS II cataract classification. Grouping eyes by Snellen acuity we found that WSCAT from the group with 6/4.5 (20/15) or 6/6 (20/20) acuity was distinguishable from the group with 6/9 (20/30) or worse acuity (95% confidence interval). Data also were analyzed using a regression model which corrects for the intraclass correlation between the two eyes of an individual. Results show a significant association between WSCAT and minimum angular resolution (MAR) derived from Snellen visual acuity (regression coefficient of 5.45, p = 0.008). WSCAT also is correlated with both LOCS II nuclear opalescence (NO) and posterior subcapsular (P) categories with regression coefficients of 3.03 (p = 0.004) and 2.07 (p = 0.054), respectively. Results from measurement of LSF indicate the potential for this instrument to assess retinal image degradation associated with nuclear and posterior subcapsular cataract objectively.

Aged↗
PubMed1993

Loss of contrast sensitivity in diabetic patients with LOCS II classified cataracts.

Contrast sensitivity function (CSF) was assessed in a population of diabetics with moderate cataracts to determine if CSF testing provides more information about visual dysfunction than Snellen or Lotmar interferometric visual acuity. With the Lens Opacities Classification Systems Version II (LOCS II) of cataract classification it was possible to grade accurately the type and severity of cataract and nuclear brunescence. The presence of statistically significant relationships between increasing LOCS II classification (worsening cataract) and diminished function, even when the regression model was controlled for Snellen visual acuity, supports the thesis that CSF measurements do provide more information about cataract related visual loss than Snellen acuity alone. Statistically significant (p < or = 0.05) relationships existed between different morphological types of cataract, nuclear colour, and CSF at specific frequencies. The frequencies affected differed with cataract type or nuclear colour, and with distance and near CSF.

Adult↗
PubMed1992

Indirect spectral transmission ratio measurements of the aging crystalline lens nucleus.

A new objective approach to characterize color and opalescence in the lens nucleus, using wavelength indexed transmission ratios (TR) is described. Transmission ratios, i.e. the transmissivity per unit lens thickness, for the whole visible spectral range (390-720 nm) were calculated using fast scanning spectral colorimetry (FSSC). The lowest transmission ratios values were obtained in the blue part of the spectrum in general and at 450 nm in particular. They inversely followed the subjectively determined LOCS II color grading. The difference between transmission ratios at the absorbed part of the spectrum (less than 500 nm) and the non-absorbed part (greater than 550 nm) also reflects the LOCS II color grading. The overall mean transmission ratios for all wavelengths in the spectrum gives an index that closely followed the nuclear opalescence grading of the LOCS II system. The transmission ratios are theoretically independent of the spectral characteristics of the incident light as long as it contains suprathreshold energies in the whole measured spectral range.

Absorption↗
PubMed1991

The Lens Opacities Case-Control Study. Risk factors for cataract.

The Lens Opacities Case-Control Study evaluated risk factors for age-related nuclear, cortical, posterior subcapsular, and mixed cataracts. The 1380 participants were ophthalmology outpatients, aged 40 to 79 years, classified into the following groups: posterior subcapsular only, 72 patients; nuclear only, 137 patients; cortical only, 290 patients; mixed cataract, 446 patients; and controls, 435 patients. In polychotomous logistic regression analyses, low education increased risk (odds ratio [OR] = 1.46) and regular use of multivitamin supplements decreased risk (OR = 0.63) for all cataract types. Dietary intake of riboflavin, vitamins C, E, and carotene, which have antioxidant potential, was protective for cortical, nuclear, and mixed cataract; intake of niacin, thiamine, and iron also decreased risk. Similar results were found in analyses that combined the antioxidant vitamins (OR = 0.40) or considered the individual nutrients (OR = 0.48 to 0.56). Diabetes increased risk of posterior subcapsular, cortical, and mixed cataracts (OR = 1.56). Oral steroid therapy increased posterior subcapsular cataract risk (OR = 5.83). Females (OR = 1.51) and nonwhites (OR = 2.03) were at increased risk only for cortical cataract. Risk factors for nuclear cataract were a nonprofessional occupation (OR = 1.96), current smoking (OR = 1.68), body mass index (OR = 0.76), and occupational exposure to sunlight (OR = 0.61). Gout medications (OR = 2.48), family history (OR = 1.52), and use of eyeglasses by age 20 years, which is an indicator of myopia (OR = 1.44), increased risk of mixed cataract. The results support a role for the nutritional, medical, personal, and other factors in cataractogenesis. The potentially modifiable factors suggested by this study merit further evaluation.

Adult↗
PubMed1991

Epidemiologic evidence of a role for the antioxidant vitamins and carotenoids in cataract prevention.

The relationship between antioxidant nutrient status and senile cataract was examined in 77 subjects with cataracts and 35 control subjects with clear lenses. Subjects with low (below the 20th percentile) and moderate (20th-80th percentiles) plasma nutrient and nutrient intake levels of vitamin C, vitamin E, and carotenoids were compared with subjects with high levels (above the 80th percentile). The odds ratio (OR) of cortical (CX) cataract among subjects with low plasma carotenoid levels was 7.2 (P less than 0.05) and the OR of posterior subcapsular (PSC) cataract for persons with low plasma vitamin C was 11.3 (P less than 0.10). Low vitamin C intake was associated with an increased risk of CX (OR = 3.7, P less than 0.10) and PSC (OR = 11.0, P less than 0.05) cataract. Subjects who consumed fewer than 3.5 servings of fruit or vegetables per day had an increased risk of both CX (OR = 5.0, P less than 0.05) and PSC cataract (OR = 12.9, P less than 0.01).

Adult↗
PubMed1990

Objective measurement of cortical and subcapsular opacification in retroillumination photographs.

An image analysis system has been developed for the objective analysis of cortical opacification. Lens photographs are obtained using a Neitz CTR retroillumination camera. The images are digitized using an IBM-PC-based imaging system. We have developed a program, called OPAC, through which the computer analyzes the image using a circular grid consisting of 93 sectors. The program outputs the percent of lens area which is opaque. Ninety-eight photographs, previously classified by the Lens Opacities Classification System (LOCS II), were analyzed using OPAC as well as a manual, square-grid counting system (GRID). The results show a linear correlation between OPAC and GRID with a correlation coefficient of 0.94. The results obtained with OPAC are also linearly correlated with the LOCS II classifications.

Cataract↗
PubMed1990

Recent studies on photodamage to the eye with special reference to clinical phototherapeutic procedures.

The use of light in clinical procedures for diagnosis and treatment has raised the possibility of adverse side effects of light on the eye. Recent studies on photobinding of sensitizers to ocular tissue, photo-oxidation of lens proteins and the role of intrinsic and extrinsic photosensitizers in cataract formation are discussed. Aspects of light damage to the retina of significance in clinical phototherapeutic procedures are outlined. Future studies that may aid in documenting and minimizing the damaging effects on the eye of long-term phototherapeutic procedures are suggested.

Crystallins↗
PubMed1989

Lens opacities classification system II (LOCS II)

The Lens Opacities Classification System, version II (LOCS II), uses a set of colored slit-lamp and retroillumination transparencies to grade different degrees of nuclear, cortical, and subcapsular cataract. The system uses four nuclear standards for grading nuclear opalescence and color, five cortical standards, and four subcapsular standards. The LOCS II can be used to grade patients' cataracts at the slit lamp or to grade slit-lamp and retroillumination photographs; it is easy to learn and can be applied consistently by different observers. We obtained very good interobserver reproducibility of the clinical gradings at the slit lamp, excellent intraobserver reproducibility, very good to excellent interobserver reproducibility of photographic gradings, and good agreement between clinical and photographic gradings. The LOCS II is potentially useful for both cross-sectional and longitudinal studies of cataract.

Cataract↗
PubMed1989

Regional sensitivity to hypoglycemia within the rabbit lens epithelium.

Paired rabbit lenses were kept in organ culture; one of the lenses was subjected to hypoglycemia, and the other served as control. The lens changes were followed and examined by photomacrography, light microscopy of the intact lens, and light and electron microscopy at different time intervals. The possibility of reversing the morphological changes was evaluated at different times by replacing the hypoglycemic medium with a normal glycemic one. The central zone of the lens epithelium was affected first through the formation of large extracellular vacuoles. These changes were reversible. Subsequently, the central lens epithelial cells showed severe swelling and breakdown of the lens membranes. These changes were not reversible. With time the epithelial changes spread from the central zone towards the equator. Lens fiber swelling followed the severe epithelial damage. These findings show that there is a regional sensitivity to hypoglycemia within the lens epithelium. The results are discussed in relation to hexokinase activity.

Animals↗
PubMed1989

Allopurinol use and the risk of cataract formation.

Several reports have suggested an association between chronic allopurinol ingestion and cortical and subcapsular cataract formation. To examine this possibility we identified 51 allopurinol users and compared their lenses with those of 76 patients who did not use allopurinol. The existence of lens opacities and the level of visual acuity were assessed by review of medical records or by prospective ophthalmic examinations; in both phases of the study the examiners were blinded as to the patient's use or non-use of allopurinol. Three different outcomes were considered: formation of any cataract, formation of a posterior subcapsular cataract, and formation of a cataract contributing to a corrected visual acuity of 20/30 or worse. The risk ratio for the formation of any cataract was 1.3 (95% confidence interval: 0.8, 2.0), the risk ratio for the formation of a posterior subcapsular cataract was 0.9 (0.3, 2.0), and the risk ratio for the formation of a cataract contributing to a loss of visual acuity was 1.3 (0.6, 2.9). None of these risk ratios was changed appreciably after controlling for age, sex, hypertension, or diabetes. Thus, after a mean of 6.9 years of allopurinol use, we found no evidence to confirm that allopurinol users were at higher risk of acquiring cataracts.

Allopurinol↗
PubMed1989

An enriched set of features of nuclear cataract identified by multidimensional scaling.

Development of an improved system for visual classification of cataracts requires a three-step procedure: first, to identify the full range of visible features of cataracts; second, to develop and test scales for the visual assessment of each feature; and third, to establish the epidemiological or clinical validity of each scale for cataract classification. This paper focuses on the first step, applying a powerful psychometric technique for identifying the visible features of nuclear cataracts. New visual features of nuclear cataract were identified using the psychometric procedure of multidimensional scaling (MDS). Each of 5 observers independently examined pairings of slitlamp photographs of 24 cases of pure nuclear cataract, making two different ratings of dissimilarity of each of the 276 possible pairs. The two dissimilarity ratings were, first, of nuclear color and, second, of nuclear structure. MDS analysis of the dissimilarity ratings of nuclear color revealed two major visual features underlying the judgments: one a combination of hue and saturation, and the other brightness. Analysis of the ratings of nuclear structure identified a total of nine features: one distinguishing between immature and mature cataracts, four describing features of the immature cataracts (aspect ratio, background haze, clarity of the embryonal nucleus, and clarity of the outer nuclear shell), and four describing features of the mature cataracts (opalescence, aspect ratio, color of the nucleus, and symmetry). We conclude that there are many more systematic distinctions to be made in the appearance of nuclear cataracts than are now recognized in clinical practice.

Cataract↗
PubMed1989

Elemental and structural studies of the rat galactose cataract.

A series of rat galactose lenses, from 1 to 20 days on the 50% galactose diet, were frozen in the whole eye, and fractured from pole to pole in the frozen state. Lyophilized half-lenses were prepared for analysis by energy dispersive spectrometry (EDS). Following elemental analysis, some specimens were embedded and sectioned for histological studies. Elemental X-ray maps, and/or profiles, were made for K, Na, Cl, Ca, P, and S. As early as two days on the galactose diet, a crescent-shaped region ("streak") of Cl, Na, and Ca gain, and K loss develops near the equatorial surface. Between this region and the equatorial surface are the nucleated differentiating fiber cells which maintain low Cl, Na, and Ca, and high K (viable equatorial zone, VEZ). With time the "streak" expands anteriorly, centrally and posteriorly, eventually (by 20 days) including most of the lens. The VEZ, including the epithelium, however, is non-reactive to the galactose diet, which is deleterious to the fully differentiated fiber cells. Eventually, the VEZ undergoes a characteristic morphological change, apparently due in part to changes in its physical environment.

Animals↗