Long-term nutrient intake and early age-related nuclear lens opacities.

OBJECTIVE: To assess the relation between usual nutrient intake and subsequently diagnosed age-related nuclear lens opacities. SUBJECTS: Four hundred seventy-eight nondiabetic women aged 53 to 73 years from the Boston, Mass, area without previously diagnosed cataracts sampled from the Nurses' Health Study cohort. METHODS: Usual nutrient intake was calculated as the average intake from 5 food frequency questionnaires that were collected during a 13- to 15-year period before the evaluation of lens opacities. The duration of vitamin supplement use was determined from 7 questionnaires collected during this same period. We defined nuclear opacities as a nuclear opalescence grade of 2.5 or higher using the Lens Opacification Classification System III. RESULTS: The prevalence of nuclear opacification was significantly lower in the highest nutrient intake quintile category relative to the lowest quintile category for vitamin C (P<.001), vitamin E (P =.02), riboflavin (P =.005), folate (P =.009), beta-carotene (P =.04), and lutein/zeaxanthin (P =.03). After adjustment for other nutrients, only vitamin C intake remained significantly associated (P =.003 for trend) with the prevalence of nuclear opacities. The prevalence of nuclear opacities was significantly lower (P<.001) in the highest vitamin C intake quintile category relative to the lowest quintile category (odds ratio, 0.31; 95% confidence interval, 0.16-0.58). There were also statistically significant trends of decreasing prevalence of nuclear opacities with increasing duration of use of vitamin C (P =.004 for trend), vitamin E (P =.03 for trend), and multivitamin (P =.04 for trend) supplements, but only duration of vitamin C supplement use remained significantly associated with nuclear opacities after mutual adjustment for use of vitamin E (P =.05 for trend) or multivitamin (P =.02 for trend) supplements. The prevalence of nuclear opacities was significantly lower (P =.004) for women who used a vitamin C supplement for 10 or more years relative to women who never used vitamin C supplements (odds ratio, 0.36; 95% confidence interval, 0.18-0.72). Plasma measures of vitamins C and E taken at the eye examination were also inversely associated with the prevalence of nuclear opacities. CONCLUSION: These results provide additional evidence that antioxidant nutrients play a role in the prevention of age-related nuclear lens opacities.

Repeated use of Bacillus subtilis cell walls for copper binding.

Purified cell walls from Bacillus subtilis were repeatedly suspended in 5 mM CuCl2 and, after removing unbound Cu, were suspended in 1% (v/v) HNO3 to release bound Cu. The walls were then regenerated by washing in H2O. After five cycles, copper binding actually increased slightly, probably due to enhanced exposure of binding sites in the walls. Thus bacterial walls may be used repeatedly for metal removal during bioremediation of heavy metal pollution.

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).

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.

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.

Quantitating nuclear opacification in color Scheimpflug photographs.

PURPOSE: To test the validity of the color component subtraction method, a new objective technique of measuring nuclear cataract, and to correlate the tangent values of the different degrees of nuclear opacities to their corresponding subjective nuclear cataract grading using the Lens Opacities Classification System II and to another objective method of measuring nuclear cataract. METHODS: Densitometries for red, green, and blue colors of the color Scheimpflug image were conducted simultaneously along the anteroposterior axis of the lens nucleus. The three color curves were subtracted from each other, giving rise to three subtracted curves: blue-red, green-blue, and red-green. This technique was applied to 99 color Scheimpflug photographs taken in 99 eyes of 51 patients with varying degrees of nuclear opacities. Using linear regression analysis, the regression coefficient obtained, called tangent value (TV), represents the degree of nuclear opacification. RESULTS: Higher tangent value indicated greater nuclear opacification and was associated with higher correlation coefficient. This was seen graphically as an increased steepness in the slope of the subtracted curve. Good correlation existed between the subjective nuclear opacity grading and the objective tangent value. When the tangent values were correlated to the mean density of the three original color curves, good correlation was present in red and green, but only fair for blue, where maximum light scattering occurs. CONCLUSIONS: These results support the validity of color component subtraction technique in measuring nuclear cataract. This technique provides quantitative measures of nuclear opacification, has good reproducibility, and is useful for monitoring nuclear cataract longitudinally.

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.

Ray tracing error correction in ophthalmic optics.

Ray tracing error correction (RTEC), a new method for various refractive calculations, is introduced. It consists of two procedures: (1) ray tracing that determines whether the ray originating from an infinite point focuses on the fovea and (2) error correction that varies the curvature of the different refractive surfaces according to an error correction formula when the ray is not focused at the fovea. These calculations are continued until the ray is focused at the fovea. The refraction of Gullstrand's schematic eye at relaxation and at accommodation, the desired postoperative corneal curvature for postoperative emmetropia after corneal ablation surgery, and the intraocular power of convex-plano, biconvex, and plano-convex intraocular lenses are presented.

New method of measuring nuclear cataract in color Scheimpflug photographs.

Based on the differential equation, a new method of measuring nuclear cataract in color Scheimpflug photographs was introduced. The densitometries for red, green and blue color were conducted simultaneously along the anteroposterior axis of the lens within the nuclear region. The 3 color components were subtracted from each other, yielding blue-red, green-red and blue-green curves which were linear within the nuclear region. The tangent values were calculated from the curves that correlate well with the degrees of nuclear cataract.

Subjective (LOCS II) versus objective (BGS) measures of cortical and subcapsular cataracts in retroillumination photographs.

96 black-and-white Neitz retroillumination photographs were graded subjectively using the Lens Opacities Classification System Version II (LOCS II). They were also measured objectively using the background subtraction (BGS) analysis. Subjective and objective BGS gradings were compared and showed good agreement (kappa = 0.78 for cortical and 0.78 for posterior subcapsular cataracts) and good correlation (correlation coefficient = 0.82 for cortical and 0.84 for posterior subcapsular cataracts; Spearman rank analysis).

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.

Strategies for measuring the rate of age-related cataract formation in vivo.

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.

Evaluation of a Lens Opacities Classification System.

A simple system, based on standard photographs, has been developed to classify lens opacities. The system allows the definition of cataract cases and noncases according to the location of lens opacification (nuclear, cortical, posterior subcapsular) and its extent (early or more advanced). Evaluation of the system has shown good to excellent reproducibility for clinical and photographic classifications. Comparisons of clinical and photograph-derived gradings has shown generally good agreement in classifying the presence and type of cataract; this agreement is highest for nuclear cataract. Photographic gradings of posterior subcapsular and, to a lesser degree, cortical opacities tend to underestimate the extent of opacification found by clinical gradings. The Lens Opacities Case-Control Study system is simple, reproducible, and easy to implement; it is offered for use in case-control and other cross-sectional studies of cataract with compatible classification goals.

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.