Lens Densities Research Articles

Comparison of corneal and lens density measurements obtained by Pentacam and CASIA2 in myopes

PurposeTo investigate the agreement between Pentacam and CASIA2 in the evaluation of corneal densities (CDs) and lens densities (LDs) in myopes.MethodsFifty-three patients (106 eyes) underwent comprehensive ophthalmologic examinations. CDs and LDs were measured using Pentacam and CASIA2, respectively, based on the grayscale percentage of the obtained images. Agreement between Pentacam and CASIA2 was evaluated using the consistency intraclass correlation coefficient (ICC) and represented using Bland-Altman plots.ResultsCompared to Pentacam, CASIA2 showed significantly higher CD and LD values in all measured zones. The ICC of the average CD and LD measured by the Pentacam and CASIA2 were 0.726 and 0.757, respectively. The ICC values of all corneal zones and lenses were above 0.7, except for the measurement of the cornea in the 0–2 mm zone (0.455), suggesting good consistency between the two devices, whose results were of different levels of linear correlation. Bland-Altman plots showed mean percentages of 3.93% for the points falling outside the limits of agreement among the densitometry results. The ICCs in different age groups were similar, but the agreement was poorer in the high myopia group (low and moderate myopia, CD: 0.739, LD: 0.753; high myopia, CD: 0.621, LD: 0.760).ConclusionsCASIA2 demonstrated good consistency with Pentacam in the measurement of CD and LD, except for measurement of CD in the central cornea and in high myopia. Despite difference in the numerical results compared with Pentacam, which made the two devices uninterchangeable, CASIA2 provides a reliable alternative densitometric measurement method.

Formulae for generating standard and individual human cone spectral sensitivities.

Normal color perception is complicated. But at its initial stage it is relatively simple, since at photopic levels it depends on the activations of just three photoreceptor types: the long- (L-), middle- (M-) and short- (S-) wavelength-sensitive cones. Knowledge of how each type responds to different wavelengths-the three cone spectral sensitivities-can be used to model human color vision and in practical applications to specify color and predict color matches. The CIE has sanctioned the cone spectral sensitivity estimates of Stockman and Sharpe (Stockman and Sharpe, 2000, Vision Res) and their associated measures of luminous efficiency as "physiologically-relevant" standards for color vision (CIE, 2006; 2015). These LMS cone spectral sensitivities are specified at 5- and 1-nm steps for mean "standard" observers with normal cone photopigments and average ocular transparencies, both of which can vary in the population. Here, we provide formulae for the three cone spectral sensitivities as well as for macular and lens pigment density spectra, all as continuous functions of wavelength from 360 to 850 nm. These functions reproduce the tabulated discrete CIE LMS cone spectral sensitivities for 2-deg and 10-deg with little error in both linear and logarithmic units. Furthermore, these formulae allow the easy computation of non-standard cone spectral sensitivities (and other color matching functions) with individual differences in macular, lens and photopigment optical densities, and with spectrally shifted hybrid or polymorphic L- and M-cone photopigments appropriate for either normal or red-green color vision deficient observers.

A Purkinje image-based system for an assessment of the density and transmittance spectra of the human crystalline lens in vivo

A method for rapid and objective assessment of ocular lens density and transmittance is needed for research and clinical practice. The aim of this study was to determine whether the Purkinje image-based technique can be used for objective and accurate quantification of spectral density and transmittance of ocular media (the mainly crystalline lens) in visible light. Twenty-six individuals (10 young, 9 middle-aged and 7 older individuals) participated in this study. Spectral lens density was evaluated by detecting the intensity of the IVth Purkinje image for different wavelengths. Subsequently, optical density index (ODI), the area under the curve in the lens density spectrum, was calculated and ODIs were compared with clinical lens opacification scales assessed subjectively using a slit lamp. Spectral lens transmittance was estimated from the lens density spectrum. Lens densities were higher in the short wavelength region of the visible spectrum across all age groups. ODI was highly correlated with the clinical opacification scale, while lens transmittance decreased with aging. Our results showed that spectral transmittance of the human crystalline lens can be easily estimated from optical density spectra evaluated objectively and rapidly using the Purkinje image-based technique. Our results provide clinicians and scientists with an accurate, rapid and objective technique for quantification of lens transmittance.

Analysis of lens epithelium telomere length in age-related cataract

We aimed to investigate the associations among lens epithelium telomere length (LETL), cataract types, and systemic pro-senescence factors in patients with age-related cataract. In this prospective study, the general demographic factors, body mass index, smoking history, depression, hypertension, diabetes, various psychological measures, and uncorrected distant visual acuity of patients with age-related cataract were recorded. Lens Opacities Classification System III (LOCS III) scores and lens density measured by Scheimpflug imaging were used to evaluate the cataracts. LETL was measured by real-time polymerase chain reaction. Correlations among these parameters were analyzed. The LOCS III nuclear opalescence (NO) score was associated with age (β = 0.053, P < 0.001) and Patient Health Questionnaire-9 score (β = −0.042, P = 0.004). Smoking was identified as a risk factor affecting LOCS III NO score (odds ratio = 1.546, 95% confidence interval, 1.128–2.119), but not the LOCS III cortical or posterior subcapsular scores. LETLs showed a weak association with systemic factors and LOCS III scores, and a significantly moderate correlation with the average objective lens densities of different regions measured by Scheimpflug imaging (r values ranged from −0.278 to −0.523, P < 0.05). However, there was no correlation between the LETLs and the maximum lens densities. The groups with a relatively low lens density had longer LETLs. In Conclusion, being an age-related disease, cortical cataract was also associated with “aging of the lens epithelium.” Notably, lens epithelium activity rarely showed systemic effects. Thus, future studies should emphasize the importance of the telomeric system in cataractous process and aging.

An objective evaluation of crystalline lens density using Scheimpflug lens densitometry in different uveitis entities.

To measure lens densities with a Pentacam HR device in patients with active uveitis. Measurements were taken at the onset of the attack and after the treatment of inflammation. The study included 51 eyes with different anterior uveitis aetiologies and a control group of 48 eyes of age- and gender-matched healthy subjects. Lens densitometry measurements were taken with a Scheimpflug camera on a Pentacam HR device. All the examinations and measurements were performed on the first presentation with the onset of the attack and were repeated at 1st and 3rd months after treatment. Lens densitometry measurements were compared with those of the healthy control group and the healthy fellow eyes of the uveitic patients. No statistically significant difference was determined between the groups in respect of age and gender (p > 0.05). At 3months, Pentacam densitometry of zones 3 value was determined to be significantly high in the uveitic eyes compared to the healthy eyes (p = 0.018). The average lens density value (ALD) at 1month was statistically significantly higher than the baseline value in the uveitic eyes (p = 0.034). There was no significant change in the ALD value at 3months compared to the baseline and 1-month values (p = 0.386, p = 0.736, respectively). Even if there is no cataract development that can be clinically observed in eyes with anterior uveitis, lens density in zone 3 showed a significant increase at the end of 3months compared to the baseline value. This change can be evaluated objectively with Scheimpflug imaging.

Heterochromatic Flicker Photometry for Objective Lens Density Quantification.

Although several methods have been proposed to evaluate lens transmittance, to date there is no consensual in vivo approach in clinical practice. The aim of this study was to compare ocular lens density and transmittance measurements obtained by an improved psychophysical scotopic heterochromatic flicker photometry (sHFP) technique to the results obtained by three other measures: a psychophysical threshold technique, a Scheimpflug imaging technique, and a clinical assessment using a validated subjective scale. Forty-three subjects (18 young, 9 middle aged, and 16 older) were included in the study. Individual lens densities were measured and transmittance curves were derived from sHFP indexes. Ocular lens densities were compared across methods by using linear regression analysis. The four approaches showed a quadratic increase in lens opacification with age. The sHFP technique revealed that transmittance decreased with age over the entire visual spectrum. This decrease was particularly pronounced between young and older participants in the short (53.03% decrease in the 400-500 nm range) wavelength regions of the light spectrum. Lens density derived from sHFP highly correlated with the values obtained with the other approaches. Compared to other objective measures, sHFP also showed the lowest variability and the best fit with a quadratic trend (r2 = 0.71) of lens density increase as a function of age. The sHFP technique offers a practical, reliable, and accurate method to measure lens density in vivo and predict lens transmittance over the visible spectrum. An accurate quantification of lens transmittance should be obtained in clinical practice, but also in research in visual and nonvisual photoreception.

Quantitative Analysis of Lens Nuclear Density Using Optical Coherence Tomography (OCT) with a Liquid Optics Interface: Correlation between OCT Images and LOCS III Grading.

Purpose. To quantify whole lens and nuclear lens densities using anterior-segment optical coherence tomography (OCT) with a liquid optics interface and evaluate their correlation with Lens Opacities Classification System III (LOCS III) lens grading and corrected distance visual acuity (BCVA). Methods. OCT images of the whole lens and lens nucleus of eyes with age-related nuclear cataract were analyzed using ImageJ software. The lens grade and nuclear density were represented in pixel intensity units (PIU) and correlations between PIU, BCVA, and LOCS III were assessed. Results. Forty-seven eyes were analyzed. The mean whole lens and lens nuclear densities were 26.99 ± 5.23 and 19.43 ± 6.15 PIU, respectively. A positive linear correlation was observed between lens opacities (R 2 = 0.187, p < 0.01) and nuclear density (R 2 = 0.316, p < 0.01) obtained from OCT images and LOCS III. Preoperative BCVA and LOCS III were also positively correlated (R 2 = 0.454, p < 0.01). Conclusions. Whole lens and lens nuclear densities obtained from OCT correlated with LOCS III. Nuclear density showed a higher positive correlation with LOCS III than whole lens density. OCT with a liquid optics interface is a potential quantitative method for lens grading and can aid in monitoring and managing age-related cataracts.

Functional Visual Acuity in Age-Related Macular Degeneration.

ABSTRACTPurposeWe evaluated whether a functional visual acuity (FVA) system can detect subtle changes in central visual acuity that reflect pathological findings associated with age-related macular degeneration (AMD).MethodsTwenty-eight patients with unilateral AMD and logMAR monocular best corrected VA better than 0 in both eyes, as measured by conventional chart examination, were analyzed between November 2012 and April 2013. After measuring conventional VA, FVA, and contrast VA with best correction, routine eye examinations including spectral domain–optical coherence tomography were performed. Standard Schirmer test was performed, and corneal and lens densities were measured.ResultsThe FVA score (p < 0.001) and visual maintenance ratio (p < 0.001) measured by the FVA system, contrast VA (p < 0. 01), and conventional VA (p < 0.01) were significantly worse in the AMD-affected eyes than in the fellow eyes. No significant differences were observed in the anterior segment conditions. Forward stepwise regression analysis demonstrated that the length of interdigitation zone disruption, as visualized by optical coherence tomography imaging, correlated with the FVA score (p < 0.01) but not with any other parameters investigated.ConclusionsThe FVA system detects subtle changes in best corrected VA in AMD-affected eyes and reflects interdigitation zone disruption, an anatomical change in the retina recorded by optical coherence tomography. Further studies are required to understand the value of the FVA system in detecting subtle changes in AMD.

SPITZERIMAGING OF STRONGLY LENSEDHERSCHEL-SELECTED DUSTY STAR-FORMING GALAXIES

We present the rest-frame optical spectral energy distribution and stellar masses of six Herschel- selected gravitationally lensed dusty, star-forming galaxies (DSFGs) at 1 < z < 3. These galaxies were first identified with Herschel/SPIRE imaging data from the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) and the Herschel Multi-tiered Extragalactic Survey (HerMES). The targets were observed with Spitzer/IRAC at 3.6 and 4.5um. Due to the spatial resolution of the IRAC observations at the level of 2 arcseconds, the lensing features of a background DSFG in the near-infrared are blended with the flux from the foreground lensing galaxy in the IRAC imaging data. We make use of higher resolution Hubble/WFC3 or Keck/NIRC2 Adaptive Optics imaging data to fit light profiles of the foreground lensing galaxy (or galaxies) as a way to model the foreground components, in order to successfully disentangle the foreground lens and background source flux densities in the IRAC images. The flux density measurements at 3.6 and 4.5um, once combined with Hubble/WFC3 and Keck/NIRC2 data, provide important constraints on the rest-frame optical spectral energy distribution of the Herschel-selected lensed DSFGs. We model the combined UV- to millimeter-wavelength SEDs to establish the stellar mass, dust mass, star-formation rate, visual extinction, and other parameters for each of these Herschel-selected DSFGs. These systems have inferred stellar masses in the range 8 x 10^10 to 4 x 10^11 Msun and star-formation rates of around 100 Msun yr-1. This puts these lensed sub-millimeter systems well above the SFR-M* relation observed for normal star-forming galaxies at similar redshifts. The high values of SFR inferred for these systems are consistent with a major merger-driven scenario for star formation.

25-Gauge Pars Plana Lensectomy With Vitrectomy

To describe a technique of 25-gauge pars plana lensectomy with primary posterior capsulotomy and sparing of the anterior lens capsule that is suitable for all lens densities. The authors describe a technique they routinely employ for pars plana vitrectomy using primarily a 25-gauge, three-port approach with intraoperative lens density assessment and possible fragmatome use for dense lenses. An analysis of the ability to achieve surgical goals is provided. Surgical goals were achieved in all 68 cases performed during an 18-month period. Anterior lens capsule was consistently spared, and 25-gauge fluidics functioned well even in the presence of a fragmatome and single 20-gauge sclerotomy. 25-gauge pars plana lensectomy with vitrectomy with and without fragmatome incision is an efficacious technique for lensectomy.

Lens density tracking in mice by Scheimpflug imaging

Scheimpflug imaging has recently been established for in vivo imaging of the anterior eye segment and quantitative determination of lens transparency in the mouse. This enables more effective investigations of cataract formation with the mouse model, including longitudinal studies. In order to enable recognition of disease-associated irregularities, we performed Scheimpflug measurements with the common laboratory inbred lines C57BL/6J, C3HeB/FeJ, FVB/NCrl, BALB/cByJ, and 129/SvJ in a period between 2 and 12months of age. C57BL/6J mice showed lowest mean lens densities during the test period. Progressive cortical lens opacification was generally observed, with the earliest onset in C57BBL/6J, C3HeB/FeJ, and 129/SvJ, between 2 and 6months after birth. Moreover, lenses of these inbred lines developed nuclear opacities. Calculated mean lens density significantly increased between 6 and 12months of age in all inbred strains except 129/SvJ. Lens densities (and the corresponding standard deviations) of FVB/NCrl and 129/SvJ increased most likely because of differences in the genetic background. Albinism as confounder might be excluded since the albino Balb/cByJ mice are more similar to the C57BL/6J or C3Heb/FeJ mice. We further identified strain-specific anterior lens opacities (C57BL/6J) and cloudy corneal lesions (C57BL/6J, FVB/NCrl, and BALB/cByJ) at later stages. In conclusion, our results indicate that there are lifelong opacification processes in the mouse lens. The highest lens transparency and a dark coat color, which prevents interference from light reflections, make mice with the C57BL/6J background most suitable for cataract research by Scheimpflug imaging. We show that lens densitometry by Scheimpflug imaging in mouse eyes can resolve differences of less than 1%, making it possible to detect differences in cataract development in different mouse strains, even if they are small.

Increased Ocular Lens Density in HIV-Infected Individuals With Low Nadir CD4 Counts in South Africa

HIV infection is thought to be associated with an increased risk of age-related morbidity and premature aging. Lens density increases with age and may function as a biomarker of aging. The relationship of lens density measurements with clinical and demographic characteristics in HIV-infected individuals in comparison with a matched population of HIV-seronegative individuals was investigated. Case-control study of 490 adults aged greater than or equal to 30 years composed of 242 HIV-infected adults and 248 age- and sex-matched HIV-seronegative individuals. Lens density was assessed using lens densitometry (Pentacam) imaging. Measurements were divided into quartiles, and comparison of HIV status and HIV-related factors was assessed by multivariate and multinomial logistic regression. The mean age was 41.2 years in HIV-infected adults and 42.3 years in HIV-seronegative individuals (P = 0.14). Of the HIV-infected adults, 88% were receiving antiretroviral therapy (ART) (median duration, 58 months), and within this group, their median CD4 count was 468 cells per microliter and 84% had undetectable viral load. Although adjusted lens densities were similar by HIV serostatus, participants on ART and who had nadir CD4 counts less than 200 cells per microliter had a higher risk of high lens density compared with HIV-seronegative individuals (P trend = 0.04). Lens density was weakly associated with detectable HIV viremia despite ART, but not with current CD4 count. HIV-infected individuals on ART with nadir CD4 counts <200 cells per microliter had increased risk of higher lens density. Lens density may represent a novel biomarker of aging, providing insight into accelerated aging trajectories in HIV infection.

Detection of early visual impairment in patients with epiretinal membrane

Patients with epiretinal membrane sometimes complain of impaired central visual function, despite good best corrected visual acuity (BCVA), as measured by visual acuity (VA) charts. Here, we evaluate early epiretinal membrane-induced changes in central VA. Subjects were 72 eyes of 36 patients with epiretinal membrane in only one eye and a BCVA in each eye better than 1.0, as measured by conventional Landolt C chart, at the Retina Division Clinic of the Department of Ophthalmology, Keio University Hospital, between December 2010 and November 2011. The conventional Landolt VA, functional VA (FVA) and contrast VA measurements were taken after a general eye examination. For the FVA, Landolt optotypes were sequentially displayed every 2 seconds, which size was changed according to the correctness of the answer. To exclude the influence of other diseases, a standard Schirmer test was performed to diagnose dry eye, and corneal and lens densities were evaluated. Average BCVA measured by Landolt C chart was not changed between affected and unaffected fellow eyes. However, the affected eyes showed a poorer FVA score (0.21 ± 0.12, affected; 0.09 ± 0.12, fellow) and visual maintenance ratio (VMR) (0.90 ± 0.04, affected; 0.94 ± 0.04, fellow), measured by the FVA system, and contrast VA score (0.35 ± 0.11, affected; 0.25 ± 0.14, fellow) than fellow eyes. The FVA and contrast VA values were correlated with the presence of epiretinal membrane, but not with the presence of dry eye, cataract and corneal densities. FVA and contrast VA results reflected early changes in central visual function caused by epiretinal membrane, which were not detected by conventional Landolt BCVA.

Effects of DL-alpha-lipoic acid on the experimentally induced diabetic cataract in rats

To investigate whether DL-alpha-lipoic acid (LA) can offer lenticular protection in diabetic rats. 36 Brown-Norway (BN) specific pathogen free (SPF) rats (7 week-old, female), were divided into 3 groups comprising of the diabetes mellitus (DM) group (14 rats), the diabetes mellitus treated with LA (DM + LA) group (14 rats), and the control (CTL) group (8 rats). The diabetic cataract was induced by streptozotocin (STZ) injection. Powdered food mixed with 0.3% LA was given to the DM + LA group, 3 days after STZ injection. Lens density was measured with EAS-1000, blood glucose and lens glutathione concentration was examined. 2 weeks after STZ injection, there was a subcapsular reticular opacity in the DM; Lens opacity became more severe and enlarged with increased duration of STZ exposure. 4 weeks later, there was slight lens opacity in the DM + LA group. After 5 weeks, there were significant differences in lens densities between the DM and the DM + LA groups (P < 0.01). 3 days after STZ injection, there was no difference between the DM and the DM + LA in blood glucose (P > 0.05); At 80 days, the concentration of blood glucose in the DM + LA was less than that of in the DM (P < 0.01). 10 months after STZ injection, there was no difference of the concentration of glutathione in lens between the DM + LA and the DM (P > 0.05). LA ingested orally can effectively reduce STZ-induced blood glucose and inhibit diabetic cataractogenesis in rats.

L, M and L–M hybrid cone photopigments in man: deriving λmax from flicker photometric spectral sensitivities

Using heterochromatic flicker photometry, we have measured the corneal spectral sensitivities of the X-chromosome-linked photopigments in 40 dichromats, 37 of whom have a single opsin gene in their tandem array. The photopigments encoded by their genes include: the alanine variant of the normal middle-wavelength sensitive photopigment, M(A180); the alanine and serine variants of the normal long-wavelength sensitive photopigment, L(A180) and L(S180); four different L–M hybrid or anomalous photopigments, L2M3(A180), L3M4(S180), L4M5(A180) and L4M5(S180); and two variants of the L-cone photopigment, encoded by genes with embedded M-cone exon two sequences, L(M2; A180) and L(M2; S180). The peak absorbances ( λ max) of the underlying photopigment spectra associated with each genotype were estimated by correcting the corneal spectral sensitivities back to the retinal level, after removing the effects of the macular and lens pigments and fitting a template of fixed shape to the dilute photopigment spectrum. Details of the genotype-phenotype correlations are summarized elsewhere (Sharpe, L. T., Stockman, A., Jägle, H., Knau, H., Klausen, G., Reitner, A. et al. (1998). J. Neuroscience, 18, 10053–10069). Here, we present the individual corneal spectral sensitivities for the first time as well as details and a comparison of three analyses used to estimate the λ max values, including one in which the lens and macular pigment densities of each observer were individually measured.

Phaco slice and separate

Phaco slice and separate retains the advantages of the chopping techniques of Nagahara, Koch, and Fukasaku but replaces chopping or snapping with slicing across the center of the phaco-tip-stabilized nucleus using a Nagahara chopper and then repositioning the chopper to optimally separate the divided lens halves. As the lens is rotated in the capsular bag, small pieces of the nuclear pie are sliced off, separated, emulsified, and aspirated. Emulsification and aspiration can alternatively be left until most or all the slices have been made. This technique works with a broader range of lens densities than other chopping techniques and uses no sculpting and very little phaco time. The phaco time required for this technique is relatively independent of nuclear density compared with a sculpting technique.

Tracing a Metameric Match to Individual Variations of Colour Vision

A metameric match may be accepted by one observer but rejected by another, indicating that the colour vision of the two observers is different. We analysed the variations of normal colour vision using metameric surfaces. First, we modelled the matches of a theoretical colour-normal observer on the Davidson and Hemmendinger (D&amp;H) colour rule (Kaiser and Hemmendinger, 1980 Color Research and Applications5 65 – 71), using spectroradiometric measurements and a set of fundamentals (Stockman, Macleod, and Johnson, 1993 Journal of the Optical Society of America A10 2491 – 2521). We also derived deviate fundamentals by changing the macular pigment density, the lens density, the photopigment density, and by shifting the long-wave sensitive photopigment. Modelling the deviate normal observer matches yields shifts of no more than 1 sample on the D&amp;H colour rule. The largest shifts are produced by changes in lens density. Second, we asked six observers to perform a match on the D&amp;H colour rule. We also estimated their macular pigment densities and their lens densities by using heterochromatic flicker photometry matches at 466 nm and 413 nm versus a 558 nm reference, and we recorded their Nagel anomaloscope setting. Then, we computed their personalised fundamentals in order to predict their D&amp;H colour matches. As the most frequent match in a sample of young observers is F-15 and the modelling for the theoretical observer yields G-15, a systematic error occurs in the predictions. After correction for this error, the results show that the metameric match of five out of six observers is better predicted by using the personalised correction of the lens and macular pigment optical density only, than by using the theoretical colour observer data.

Aging of the human crystalline lens and anterior segment

Changes in the unaccommodated human crystalline lens were characterized as a function of subject age for 100 normal emmetropes over the age range 18–70 yr by Scheimpflug slit-lamp photography. With increasing age, the lens becomes thicker sagittally, but since the distance from the cornea to the posterior lens surface remains unchanged, this indicates that the center of lens mass moves anteriorly and the anterior chamber becomes shallower. Sagittal nuclear thickness is independent of age, but both anterior and posterior cortical thicknesses increase with age, shifting the location of the nucleus and the central sulcus in the anterior direction. The amount of light scattered by the lens at high angles, as represented by normalized and integrated lens densities from the digitized images, increases with increasing age in an exponential fashion. Similar relationships to age are observed for the major anterior zone of discontinuity (maximum density) and the central sulcus (minimum density). The relationships of these results to accommodation and presbyopia are discussed.

Physiological causes of individual variations in color‐matching functions

AbstractThe present study confirms that the individual variations of Stiles' 20 color‐matching functions are physiologically well predicted by those of eye lens and macular optical densities. The principal‐component analysis of the blue color‐matching functions shows the significance of the two independent spectral components, which are expected to correspond to lens and macular optical densities. The lens and the macular densities for each of Stiles' 20 observers are estimated by using their published data physiologically measured. The estimated densities predict well each of Stiles' 20 color‐matching functions. The singular‐value decomposition of the estimated 20 color‐matching functions provides a good estimate of the standard‐deviate observer derived from the original Stiles 20 color‐matching functions by using the same procedure.

A rapid method to assess crystalline lens pigment density in vivo.

A procedure for rapidly estimating lens pigment density, based upon metameric matches on the D & H Color Rule, is described. A computational nomograph to convert settings to lens densities is provided. This procedure was validated in a sample 126 normal observers, and shown to produce data comparable to more complex laboratory testing procedures. The speed and simplicity of this procedure suggest that it may be useful for monitoring changes in lens pigment density in groups exposed to high levels of environmental, laboratory or industrial ultraviolet light.