Y Sakamoto

Kanazawa Medical University, Kanazawa-shi, Ishikawa-ken, Japan

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Publications (40)30.33 Total impact

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    ABSTRACT: To evaluate low-dose X-ray radiation effects on the eye by measuring the amount of light scattering in specific regions of the lens, we compared exposed subjects (interventional radiologists) with unexposed subjects (employees of medical service companies), as a pilot study. According to numerous exclusionary rules, subjects with confounding variables contributing to cataract formation were excluded. Left eye examinations were performed on 68 exposed subjects and 171 unexposed subjects. The eye examinations consisted of an initial screening examination, followed by Scheimpflug imaging of the lens using an anterior eye segment analysis system. The subjects were assessed for the quantity of light scattering intensities found in each of the six layers of the lens. Multiple stepwise regression analyses were performed with the stepwise regression for six variables: age, radiation exposure, smoking, drinking, wearing glasses and workplace. In addition, an age-matched comparison between exposed and unexposed subjects was performed. Minimal increased light scattering intensity in the posterior subcapsular region showed statistical significance. Our results indicate that occupational radiation exposure in interventional radiologists may affect the posterior subcapsular region of the lens. Since by its very nature this retrospective study had many limitations, further well-designed studies concerning minimal radiation-related lens changes should be carried out in a low-dose exposure group.
    Journal of Radiation Research 11/2012; · 1.45 Impact Factor
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    ABSTRACT: To investigate the lipid and DNA oxidative stress as well as corneal and retinal effects after ultraviolet B (UV-B) exposure in mice, with or without silicon hydrogel soft contact lenses (SCL). Twenty-eight C57BL6-strain male mice were divided into four groups: group I, control group with no SCL (SCL [-]) and no UV-B exposure (UV-B [-]); group II, senofilcon A SCL (senofilcon [+]) with UV-B exposure (UV-B [+]); group III, lotrafilcon A SCL (lotrafilcon [+]) with UV-B exposure (UV-B [+]); and group IV, no SCL (SCL [-]), but with UV-B exposure (UV-B [+]). All mice except group I received UV-B exposure for 5 days for a total dose of 2.73 J/cm(2). All mice underwent tear hexanoyl-lysine (HEL) and tear cytokine ELISA measurements, and fluorescein and rose bengal corneal staining before and after UV-B exposure. Corneal specimens underwent immunohistochemistry staining with CD45, HEL, 4-hydroxynonenal (4-HNE), and 8-hydroxy-2'-deoxyguanosine (8-OHdG) antibodies and evaluation with electron microscopy. All mice without SCL but exposed to UV-B developed corneal edema, ulcers, or epithelial damage compared with mice with senofilcon A SCL and exposure to UV-B. Tear HEL and cytokine levels significantly increased in mice without SCL after UV-B exposure. Immunohistochemistry showed a significantly higher number of cells positively stained for CD45, 8-OHdG, HEL, and 4-HNE in the corneas of mice without SCLs compared with those with senofilcon A after UV-B exposure. Silicon hydrogel SCL showed corneal and retinal protective effects, owing to UV blocking properties, against oxidative stress-related membrane lipid and cellular DNA damage.
    Investigative ophthalmology & visual science 03/2012; 53(4):2403-13. · 3.43 Impact Factor
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    ABSTRACT: To assess the validity of the solar ultraviolet index (UVI) as a determiner of eye risk under different conditions of facial profiles and orientation, and reflected light. Ocular UV radiation (UVR) exposure was measured as a function of the time of the day (solar altitude) using a two-dummy-type mannequin dosimetry system with embedded UVR (260-310 nm) sensors, in September and November in Kanazawa, Japan, on a motorized sun-tracking mount with one dummy face directed toward the sun and the other away from the sun. A bimodal distribution of UV-B exposure was found in September for the face directed toward the sun, which differed dramatically from the pattern of ambient UVR exposure and measurements taken on the top of the head and those for the eye taken later in the year. Although the overall level was lower, a higher solar altitude is associated with higher UVR exposure in the condition facing away from the sun. The UVI is based on ambient solar radiation on an unobstructed horizontal plane similar to our measures taken on the top of the head, which differed so much from our measures of ocular exposure that UVI as a determiner of eye risk is deemed invalid. The use of the UVI as an indicator for the need for eye protection can be seriously misleading. Doctors should caution patients with regard to this problem, and eye protection may be warranted throughout the year.
    Eye & contact lens 07/2011; 37(4):191-5.
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    ABSTRACT: To compare visual acuity and ocular higher-order aberrations (HOAs) in eyes with waterclefts, a type of crystalline lens opacity, and in normal eyes. Department of Ophthalmology, Kanazawa Medical University, Ishikawa, Japan, and Faculty of Medicine, University of Iceland, Reykjavik, Iceland. In this nested case-control study of subjects attending the third examination of the Reykjavik Eye Study in 2008, eyes with pure waterclefts and control eyes with no lenticular opacity were evaluated. All candidates had complete ophthalmic examinations and wavefront analysis. Higher-order aberrations in the watercleft group and the control group were compared. The watercleft group comprised 30 eyes and the control group, 194 eyes. The mean corrected distance visual acuity (CDVA) in the watercleft group was statistically significantly lower than in the control group (P<.01). There was a significant relationship between CDVA and HOA in both groups. Total HOA and trefoil and coma aberrations were statistically significantly higher in the watercleft group than in the control group (P<.05). Waterclefts significantly affected CDVA. Eyes with waterclefts had higher coma and trefoil aberrations, suggesting that the increased HOAs caused reduced visual acuity in eyes with waterclefts.
    Journal of Cataract and Refractive Surgery 05/2010; 36(5):799-805. · 2.75 Impact Factor
  • Journal of Vascular and Interventional Radiology - J VASC INTERVEN RADIOL. 01/2009; 20(2).
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    ABSTRACT: alpha-Lipoic acid (LA) is well known as a powerful antioxidant. The efficacy of dihydrolipoate-LA for oral administration against streptozotocin (STZ)-induced diabetic cataract in rat was investigated. Rats were divided into three groups, control, diabetes mellitus (DM), and DM treated with LA (DM+LA). Diabetes was induced by intravenous injection of 50 mg/kg STZ. DM+LA rats were fed 30 mg/rat per day LA in their diet. Lens changes were assessed using Scheimpflug images (EAS-1000) and by measuring light-scattering intensity. Increase in lens light scattering was less (P < 0.05) in DM+LA rats than in DM rats 5 weeks after induction of diabetes. DM rats had the highest and control rats the lowest blood glucose levels at every measurement point up to 111 days (P < 0.05). LA treatment delayed development and progression of cataract in rats with streptozotocin-induced diabetes.
    Japanese Journal of Ophthalmology 01/2007; 51(1):10-3. · 1.27 Impact Factor
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    ABSTRACT: Sunglasses have generally been used to protect against glare. Various kinds of sunglasses which correspond to the visual environment are on the market (e.g. for driving, fishing, skiing, etc.). As for the spectral transmission factor of sunglasses, the differences that occur in user's eyes with aging have not been fully considered. We investigated the relationship between different levels of crystalline lens transparence and the effects of glare protection using two kinds of filters. A Tri-Blocker filter (TB) and general driving filter (ActiveDrive, ADR) were used. The TB absorbs three spectral wavelengths (below 400 nm, blue light, 575 nm) and can be transparent for other visible light. The ADR reduces the light below 650 nm. TB and ADR transmit 52.5 and 29.0% of the visible light, respectively. Twenty-five normal volunteers with transparent lenses (n = 48 eyes, aged from 22 to 68 years) and 10 cortical cataract patients (n = 18 eyes, aged from 48 to 71 years) were selected. The visual acuity of all subjects was 1.0 or better with the best correction. Contrast sensitivity function (CSF) was measured in four simulated light conditions (daylight, daylight with peripheral glare, twilight, twilight with central glare) by MCT8000 (Vistech). The light scattering intensity of the crystalline lens was measured by EAS-1000 (Nidek). The TB improved the CSF of the elderly volunteers under daylight conditions and of 1 of the cataract patients under all conditions. In the younger group, the CSF did not change under daylight conditions and deteriorated under twilight conditions. Although the ADR was effective for glare protection in the young volunteers, the protective effects of the TB were better than those of ADR for the middle-aged group. Sunglasses not only protect against glare but also stabilize visual quality under various light conditions (e.g. passing through a tunnel while driving). Aging changes in lens transparency should be specially considered when developing protective eyewear.
    Developments in ophthalmology 02/2002; 35:93-103.
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    ABSTRACT: To predict the postoperative anterior chamber (AC) depth from the preoperative in situ position of the lens central clear zone (CCZ) using Scheimpflug slit photography. 111 eyes of 78 cases that underwent phacoemulsification and intraocular lens (IOL) implantation were examined. 748 eyes of 383 healthy subjects with transparent lenses were used as the control. Scheimpflug slit photography was done under maximal mydriasis, and biometry was performed on the photographs. Two types of acrylic IOLs (MA30BA and MA60BM, both from Alcon) were used in this study. The preoperative AC depth (L1), the distance between the anterior lens capsule and lens CCZ (L2) and the postoperative AC depth (I1) were determined. I2, the predicted postoperative AC depth, was then determined from a linear regression of L1 + L2 and I1. L2 thickened by 0.014 mm/year, and L1 decreased by 0.016 mm/year in the transparent lenses. L1 + L2 changed little with aging in both cataractous and transparent lenses. L1 + L2 and I1 showed a linear correlation with r = 0.80 in the MA30BA and r = 0.77 in the MA60BM groups. The mean error values between I1 and I2 were 0.095 +/- 0.096 and 0.123 +/- 0.114 mm in MA30BA and MA60BM, respectively. The error between I1 and I2 was within +/- 0.17 and +/- 0.33 mm or less in 72.9 and 91.5% of MA30BA and in 82.7 and 96.2% of MA60BM. In contrast, the error between I2 and I1 when calculated using the SRK/T formula was much larger - in excess of +/- 0.33 mm in 38.7% of the eyes. L1 + L2 changes little with aging and is considered a useful marker of the position of the crystalline lens in situ. There was a high correlation between I1 and L1 + L2. These allow a far more accurate prediction of I1 than previous methods. In combination with the conventional regression formula and ray tracing, a highly accurate IOL power calculation can be attained.
    Ophthalmic Research 01/2002; 34(5):265-72. · 1.56 Impact Factor
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    ABSTRACT: The frequency and characteristics of cortical cataract localization within a dilated pupillary area were investigated in a population-based cataract epidemiological survey performed in the city of Reykjavik in Iceland. Among 1045 randomly selected individuals, the right eyes of 277 persons with mild cortical lens opacification (Grade I) were selected for our study. The localization of cortical cataracts was examined using retroillumination images, which were divided into 56 circular and radial sections, and calculations were made of the percentages for each opacified area. A questionnaire was used to record the number of hours spent outdoors during week days, the time of the day and whether the subjects wore spectacles, sunglasses or hats when outside. The percentage of cortical opacification was significantly higher in the lower nasal quadrant than in all other quadrants (p < 0.05). Furthermore, the percentage of opacification localized in the lower nasal quadrant was higher in individuals with a longer history of outdoor activity than those without (p < 0.05). The percentage of opacification in individuals, who have had the habit of wearing sunglasses for outdoor activities lasting longer than half an hour during weekdays in their 20's and 30's was lower in all quadrants and statistically significantly lower in the upper temporal quadrant (p < 0.05) compared to those not wearing sunglasses. This suggests that wearing sunglasses is effective in preventing the development and/or progression of cortical cataracts.
    Klinische Monatsblätter für Augenheilkunde 02/2001; 218(2):78-84. · 0.70 Impact Factor
  • Klinische Monatsblatter Fur Augenheilkunde - KLIN MONATSBL AUGENHEILK. 01/2001; 218(2):78-84.
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    ABSTRACT: Recently, the rapid progression of cataract surgical technique has led cataract patients in industrialized countries to ignore the possibilities of drug therapy. Globally, however, it will be impossible in the near future to treat cataract by surgery alone, mainly due to medicoeconomic reasons. Preventative measures must be sought. As one of the these measures, the development of anticataractogenic drugs has reemerged as a focus in the lens research field. Although clinical trials of newly developed drugs are absolutely necessary before they enter the market, they have been considered to be a rather easy task. However, in order to gain accurate and reproducible data from trials, the trial program must be carefully prepared. The numbers of participants to the trial, the selection criteria of the subjects, the objective judgment of cataractous changes, follow-up period, a high technical level for cataract documentation and image analysis are proposed. Although there still remain some difficulties concerning the methods for objective judgment, a scientifically acceptable examination must be conducted.
    Ophthalmologica 02/2000; 214(6):390-8. · 1.41 Impact Factor
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    ABSTRACT: Purpose: An epidemiological survey of ocular disease was performed in a town of the Amami Islands in southwestern Japan.Object and Methods: A total of 339 participants over 40 years joined the survey. Among the 339 participants, the lens findings of 602 eyes of 301 subjects were analyzed.Results: The prevalence of lens opacification was 32.0, 54.0, 83.1, 96.9%, and 100% among subjects in their 40, 50, 60, 70s, and over 80 years. Lens opacification over grade II was 4.0, 12.7, 26.2, 60.0%, and 83.3%. The cataract type most frequently seen was cortical (96.1%), followed by 48.5% with nuclear opacity and 14.7% with subcapsular type. A high prevalence was seen of pterygium at 25.4%. Although the prevalence of lens opacification was higher in the group with pterygium in their 70s, no significant difference was noticed in persons in their 40, 50, 60s, and over 80 years old between the pterygium and non-pterygium groups.Conclusions: Similarly to the results of a previous survey in Okinawa, Noto, and Hokkaido, the main type of lens opacification was cortical in Amami. The prevalence of nuclear opacification and pterygium was higher than in Noto and Hokkaido, and close to that seen in Okinawa.
    Japanese Journal of Ophthalmology - JPN J OPHTHALMOL. 01/2000; 44(1):97-97.
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    ABSTRACT: UV irradiation has the potential to induce the development of lens opacities. This has been demonstrated since long with animal experiments. Unfortunately these animal cataracts did not explain or elucidate the epidemiological observation that the frequency of human cataracts--such as the so called senile cataract--is remarkably higher in regions with increased cosmic UV irradiation or in the population being in close professional contact with UV-irradiation. The main problem was that the type of UV induced animal cataracts differs remarkably with respect to onset, localization of the opacity, size and its timely progression from the cataract classes observed in human. The research of the last 10 years comes to the conclusion that beside the direct (acute) damage--as seen in animal studies due to high UV dosages--we have to realize a syn- or co-cataractogenic potential of UV irradiation even below the threshold dose which is able to accumulate in the lens and to initiate together with other risk factors (chronic damage) the opacification of the lens. The mechanism for the animal cataract and the human cataract (with an UV risk participation) are different. The epidemiological research about cataract frequency in different regions of the world have to take into account that UV irradiation--even below a threshold dose--is a possible risk among the multifactorial pathogenesis of human cataract.
    Journal of Epidemiology 01/2000; 9(6 Suppl):S39-47. · 2.11 Impact Factor
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    ABSTRACT: An epidemiological survey of ocular disease was performed in a town of the Amami Islands in southwestern Japan. A total of 339 participants over 40 years joined the survey. Among the 339 participants, the lens findings of 602 eyes of 301 subjects were analyzed. The prevalence of lens opacification was 32.0, 54.0, 83.1, 96.9% and 100% among subjects in their 40, 50, 60, 70 s, and over 80 years. Lens opacification over grade II was 4.0, 12.7, 26.2, 60.0% and 83.3%. The cataract type most frequently seen was cortical (96.1%), followed by 48.5% with nuclear opacity and 14.7% with subcapsular type. A high prevalence was seen of pterygium at 25.4%. Although the prevalence of lens opacification was higher in the group with pterygium in their 70 s, no significant difference was noticed in persons in their 40, 50, 60 s, and over 80 years old between the pterygium and non-pterygium groups. Similarly to the results of a previous survey in Okinawa, Noto, and Hokkaido, the main type of lens opacification was cortical in Amami. The prevalence of nuclear opacification and pterygium was higher than in Noto and Hokkaido, and close to that seen in Okinawa.
    Nippon Ganka Gakkai zasshi 08/1999; 103(7):556-63.
  • Y Sakamoto, M Kojima, K Sasaki
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    ABSTRACT: The relationship between eyeglass size and protection of the eye surface from the effects of solar ultraviolet (UV) rays was investigated. Solar UV rays irradiating the eye surface were measured on a mannequin which modeled the standard facial bone structure of a Japanese female. UV sensor chips (photo-sensitivity: 260-400 nm) were attached to the ocular surface of the lid fissure. UV measurement was done from 12:00 to 15:00 on a sunny day in March. UV intensity was measured under the following conditions: 1) with or without eyeglasses, 2) wearing sunglasses with side protectors, and 3) wearing a cap with a 7 cm brim. Eyeglasses of four frame sizes (width: 48-57 mm) were put on the mannequin. All lenses were made of plastic and coated so as to be impervious to rays shorter than 400 nm. The refractive power was 0 diopters. At the same time, UV irradiation intensity from all directions (excluding from the earth direction) was measured using a polyhedron type UV sensor with 25 sensor chips. Except for eyeglasses with the smallest frame size, eyeglasses effectively reduced UV exposure to sunlight from the upper front direction. However, protection against rays from the upper temporal direction was extremely poor. Sunlight from the upper back was reflected by the posterior surface of the eyeglasses and reached the eye surface. The efficacy of eyeglasses against UV depends on their size. The shape of the eyeglasses and reflection from the posterior lens surface are also of great importance. Small eyeglasses do not offer ideal UV protection for the Japanese face shape.
    Nippon Ganka Gakkai zasshi 06/1999; 103(5):379-85.
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    ABSTRACT: The light scattering intensity of normal, clear lenses varies with age and with the localization within the lens. Realizing the biometry of single lens areas together with their relevant light scattering intensity one should be able to calculate an index to express the lens transparency properties of normal human lenses in dependence on age. Performing the same procedure in cases of diabetic patients with still clear lenses it should become possible to obtain an index for the lens transparency properties of lenses under the 'risk factor' diabetes. 748 eyes with transparent lenses in 383 healthy individuals and 134 eyes with clear lenses in 70 subjects with diabetes were examined. Scheimpflug slit images of the lens were documented by a Nidek EAS-1000 instrument. Biometry for measuring the distance of the single lens layers from the anterior capsule and densitometry for determining the light scattering intensity of six defined lens layers along the (theoretical) optical axis were performed. The index of the lens transparency properties was calculated using the light scattering intensity of a defined lens layer and its distance from the anterior capsule. Lens thickness and light scattering intensities increased linearly with increasing age in the normal population as well as in the diabetic patients. The densitogram pattern of the light scattering intensities in the defined representative six points was similar in both populations, but in the diabetic group the lens thickness was larger and the light scattering intensities were higher at all ages. The index of lens transparency properties calculated with the light scattering intensities of a certain lens area and its distance from the anterior capsule is a useful measure of lens clarity in dependence on age. 'Clear' lenses of the diabetic population show significantly higher indices for the lens transparency properties in all age groups.
    Ophthalmic Research 02/1999; 31(2):93-103. · 1.56 Impact Factor
  • Y Sakamoto, H Nakaizumi, K Sasaki
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    ABSTRACT: In order to objectively evaluate the relationship between the quality of images which will be reflected on the retina, through opaque lenses and the grade of opacification, model lenses of nuclear cataract and subcapsular cataract were manufactured. The nuclear cataract model lenses were made of polymethylmethacrylate (PMMA) with and without a cut off wavelength below 380 nm. The lens shape was the biconvex intraocular lens (IOL) type and the opacification was achieved by polymerization of both hydrophile and lyophobic monomers. The model of subcapsular opacification was composed of ultraviolet (UV)-cut IOL and a hard contact lens (HCL). The HCL was attached behind the IOL and whitish corpuscles (T1O2, mean diameter of particle = 0.2 micron) were inserted into the gap between the lenses. Utilizing a still camera with 35 mm film, images were photographed through the nuclear opacified model lenses and evaluated. The model of the subcapsular opacified lens was examined by a simulation camera (CCD) in which the lens was held in water. The image quality obtained from the non-UV absorbed nuclear opacification type lens was markedly poor compared with that from the UV absorbed type lens. Although image contrast became worse with increased nuclear opacification, the worsening of image quality was slight in the opacified lens with a 20% reduction of light transmission. It was even possible to recognize photographed subjects through an opacified lens with 60% transmission. Images through the subcapsular opacified model lenses were not influenced by the opacified area in the models with up to 130 cct light scattering intensity at the central part of opacification. Although the study aimed to simply simulate images reflected on the retina through two types of cataractous lenses, the results obtained showed useful objective information concerning images seen through cataractous eyes.
    Nippon Ganka Gakkai zasshi 06/1998; 102(5):312-8.
  • Y Sakamoto, M Kojima, Y Emori, K Sasaki
    Developments in ophthalmology 02/1997; 27:50-5.
  • Developments in ophthalmology 02/1997; 27:56-62.
  • Developments in ophthalmology 02/1997; 27:32-41.