Robert W. McClane

Resonance Raman measurement of macular carotenoids in normal subjects and in age-related macular degeneration patients

PURPOSE Dietary carotenoids lutein and zeaxanthin may play a protective role against visual loss from age-related macular degeneration (AMD) through antioxidant and light screening mechanisms. We used a novel noninvasive objective method to quantify lutein and zeaxanthin in the human macula using resonance Raman spectroscopy and compared macular pigment levels in AMD and normal subjects. DESIGN Observational study of an ophthalmology clinic-based population. PARTICIPANTS AND CONTROLS Ninety-three AMD eyes from 63 patients and 220 normal eyes from 138 subjects. METHODS Macular carotenoid levels were quantified by illuminating the macula with a low-power argon laser spot and measuring Raman backscattered light using a spectrograph. This technique is sensitive, specific, and repeatable even in subjects with significant macular pathologic features. MAIN OUTCOME MEASURE Raman signal intensity at 1525 cm(-1) generated by the carbon-carbon double-bond vibrations of lutein and zeaxanthin. RESULTS Carotenoid Raman signal intensity declined with age in normal eyes (P < 0.001). Average levels of lutein and zeaxanthin were 32% lower in AMD eyes versus normal elderly control eyes as long as the subjects were not consuming high-dose lutein supplements (P = 0.001). Patients who had begun to consume supplements containing high doses of lutein (> or =4 mg/day) regularly after their initial diagnosis of AMD had average macular pigment levels that were in the normal range (P = 0.829) and that were significantly higher than in AMD patients not consuming these supplements (P = 0.038). CONCLUSIONS These findings are consistent with the hypothesis that low levels of lutein and zeaxanthin in the human macula may represent a pathogenic risk factor for the development of AMD. Resonance Raman measurement of macular carotenoid pigments could play an important role in facilitating large-scale prospective clinical studies of lutein and zeaxanthin protection against AMD, and this technology may someday prove useful in the early detection of individuals at risk for visual loss from AMD.

In vivo resonant Raman measurement of macular carotenoid pigments in the young and the aging human retina

We have used resonant Raman scattering spectroscopy as a novel, noninvasive, in vivo optical technique to measure the concentration of the macular carotenoid pigments lutein and zeaxanthin in the living human retina of young and elderly adults. Using a backscattering geometry and resonant molecular excitation in the visible wavelength range, we measure the Raman signals originating from the single- and double-bond stretch vibrations of the pi-conjugated molecules carbon backbone. The Raman signals scale linearly with carotenoid content, and the required laser excitation is well below safety limits for macular exposure. Furthermore, the signals decline significantly with increasing age in normal eyes. The Raman technique is objective and quantitative and may lead to a new method for rapid screening of carotenoid pigment levels in large populations at risk for vision loss from age-related macular degeneration, the leading cause of blindness in the elderly in the United States.

Resonance Raman detection of carotenoid antioxidants in living human tissues

We have used resonance Raman scattering as a novel noninvasive optical technology to measure carotenoid antioxidants in living human tissues of healthy volunteers. By use of blue-green laser excitation, clearly distinguishable carotenoid Raman spectra superimposed on a fluorescence background are obtained. The Raman spectra are obtained within less than a minute, and the required laser light exposure levels are well within safety standards. Our technique can be used for rapid screening of carotenoid levels in large populations and may have applications for assessing antioxidant status and the risk for diseases related to oxidative stress.

Resonant Raman detection of macular pigment levels in the living human retina

We have used resonant Raman scattering as a novel, noninvasive in vivo optical technique to measure the concentration of macular carotenoid pigments in the living human retina. Using a backscattering geometry and resonant molecular excitation in the visible, we measure the Raman peaks that originate from the single- and double-bond stretch vibrations of the p -conjugated molecules carbon backbone. The Raman signals scale linearly with carotenoid content, whereas the required laser excitation is well under safety limits for macular exposure. The Raman technique is objective and quantitative and may lead to a new method for rapid screening of carotenoid pigment levels in large human populations that are at risk for vision loss from age-related macular degeneration, the leading cause of blindness of the elderly in the United States.

FL-41 Tint Improves Blink Frequency, Light Sensitivity, and Functional Limitations in Patients with Benign Essential Blepharospasm

OBJECTIVE The objective of these 2 studies was to assess the efficacy of FL-41-tinted lenses in the treatment of benign essential blepharospasm (BEB). DESIGN A randomized crossover study and a randomized crossover case-control study. PARTICIPANTS The first study included 30 subjects with BEB. The second study included 26 subjects with BEB and 26 controls. METHODS For the first study, subjects were randomized to wear either FL-41 or gray-tinted lenses for 2 weeks. After a 2-week washout period, the other lens was worn for 2 weeks. Questionnaires were completed at baseline, after the first lens, and after the second lens. In the second study, surface electromyography (EMG) was used to measure blink frequency, duration, and force while subjects read and wore FL-41, rose, or gray-tinted lenses. MAIN OUTCOME MEASURES Questionnaires were used to assess perceptions of light sensitivity and the effect of light sensitivity on activities of daily living (ADL). EMG was used to measure blink frequency, duration, and force. RESULTS Most participants observed improvement while wearing both FL-41 and gray-tinted lenses. FL-41-tinted lenses provided superior improvement in the areas of reading, fluorescent light sensitivity, overall light sensitivity, blepharospasm frequency, and blepharospasm severity. FL-41 lenses reduced mean blink rate compared with both rose and gray-tinted lenses, and reduced eyelid contraction force compared with rose-tinted lenses. CONCLUSIONS FL-41 lenses provided both subjective and objective benefit to subjects with BEB. Physicians should consider recommending this noninvasive and inexpensive lens tint to patients with BEB. FINANCIAL DISCLOSURE(S) Proprietary or commercial disclosure may be found after the references.

Application of charge-coupled device technology for measurement of laser light and fluorescence distribution in tumors for photodynamic therapy.

Abstract— —Laser and fluorescence light distributions with applications for photodynamic therapy were measured in mouse tumors using a non‐invasive electronic optical imaging system. The system consists of a liquid‐nitrogen‐cooled, charge‐coupled‐device (CCD) array camera under computer control with 576 × 384 detection elements having dimensions of 23 μm × 23 μm. The available dynamic range of the array is approx. 103, and the effective wavelength range is 400–1000 nm. An interstitially placed cylindrical diffusing optical fiber was used to provide tumor illumination. The light distribution pattern from the fiber was determined by immersing the cylindrical diffusing tip in a fluorescing solution and recording the emission image. Fluorescence imaging facilitates an accurate measurement of light intensity distribution while avoiding problems associated with the directional nature of other detection methods used with diffusing fibers. Radiation‐induced fibrosarcoma tumors on C3H mice were grown to about 1 cm diameter for in vivo recording of light distribution from the tumor volume and for determination of effective light penetration distance at 18 wavelengths in the range 458–995 nm. Endogenous tumor fluorescence and Photofrin II fluorescence intensity were measured over the wavelength range 585–725 nm to investigate the possible application of CCD imaging technology for drug distribution measurements. Model experiments were begun to evaluate the relative importance of potential distortions of light distribution measurements using this approach.

Raman detection of carotenoid pigments in the human retina

We have used resonant Raman scattering as a novel, non- invasive, in-vivo optical technique to measure the concentration of macular carotenoid pigments in the living human retina of young and elderly adults. Using a backscattering geometry and resonant molecular excitation in the visible, we measure the Raman peaks originating from the single- and double-bond stretch vibrations of the (pi) - electron conjugated molecules carbon backbone. The Raman signals scale linearly with carotenoid content while the required laser excitation is well below safety limits for macular exposure. Measured macular pigment levels decline significantly with increasing age. The Raman technique is objective and quantitative and may lead to a new method for rapid screening of carotenoid pigment levels in large populations at risk for vision loss from age-related macular degeneration, the leading cause of blindness in the elderly in the United States.

Noninvasive laser Raman detection of carotenoid antioxidants in living human skin

We have used resonance Raman scattering as a novel non- invasive optical technology to measure carotenoid antioxidants in human skin of healthy volunteers. Using blue-green laser excitation, clearly distinguishable carotenoid Raman spectra are obtained which are superimposed on a large skin autofluorescence background. The Raman spectra are obtained rapidly, i.e. within about 30 seconds, and the required laser light exposure levels are well within safety standards. Our technique can be used for rapid screening of carotenoid antioxidant levels in large populations and may have applications for assessing the risk for cutaneous diseases.

In-vitro CCD measurements of light distributions from diffusing optical fiber tips used in photodynamic therapy

An electronic optical imaging system consisting of a computer-controlled CCD array with 576 x 384 detection elements and 14 bits of digitization is presented. The system is used to obtain internal and external light intensity distributions for diffusing optical fiber tips used with photodynamic therapy and laser angioplasty. Significant intensity distribution variations were observed between fiber tips from 5 different sources. The effect of launch numerical aperture on the measured light distributions is also presented.

Raman imaging of carotenoid pigments in the human retina

We have generated high spatial resolution images showing the distribution of carotenoid macular pigments in the human retina using Raman spectroscopy. A low level of macular pigments is associated with an increased risk of developing age-related macular degeneration, a leading cause of irreversible blindness. Using excised human eyecups and resonant excitation of the pigment molecules with narrow bandwidth blue light from a mercury arc lamp, we record Raman images originating from the carbon-carbon double bond stretch vibrations of lutein and zeaxanthin, the carotenoids comprising human macular pigments. Our Raman images reveal significant differences among subjects, both in regard to absolute levels as well as spatial distribution within the macula. Since the light levels used to obtain these images are well below established safety limits, this technique holds promise for developing a rapid screening diagnostic in large populations at risk for vision loss from age-related macular degeneration.