Kazuyuki Sasaki

UV-B exposure to the eye depending on solar altitude

Purpose: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. Methods: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. Results: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. Conclusions: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.

Effect of 5-S-GAD on UV-B-induced cataracts in rats

Purpose5-S-Glutathionyl-N-β-alanyl-3,4-dihydroxyphenylalanine (5-S-GAD) is a novel antibacterial substance purified from Sarcophaga peregrina (flesh fly) that has both a radical scavenging activity and antioxidative activity. This is a report of an investigation of the effect of 5-S-GAD (eyedrops) on UVB-induced cataracts in rats.MethodsBrown Norway male rats (n = 32; 7 weeks old) were treated with either 5-S-GAD 0.1%, 5-SGAD 1%, astaxanthin (AST) 0.1% suspension eyedrops or the vehicle alone (the solution without 5-S-GAD) three times a day (three doses at 5-min intervals each time). The treatment was scheduled 2 days before UV-B exposure and 2 days after UV-B exposure. Exposure to 100–200 mJ/cm2 UV-B was performed once a week between drug treatments for 9 consecutive weeks, with a total dose of 1200 mJ/cm2 UV-B. Ocular penetration of 5-S-GAD was analyzed using high-pressure liquid chromatography (HPLC). Cataract formation was documented by an anterior eye segment analysis system once a week under mydriasis. The light-scattering intensity (LSI) of the anterior superficial cortex region was measured.ResultsIn the eighth to ninth week after the start of UV-B exposure, the LSI of anterior subcapsular lenses of 5-S-GAD-treated groups, as detected by HPLC, was significantly lower (P < 0.05) than that of the control, whereas no such difference was found in the AST-treated group.Conclusion5-S-GAD eyedrop application may delay the progression of UV-B-induced cataract in rats.

FDTD analysis of temperature elevation in the lens of human and rabbit models due to near-field and far-field exposures at 2.45 GHz

The eye is said to be one of the most sensitive organs to microwave heating. According to previous studies, the possibility of microwave-induced cataract formation has been experimentally investigated in rabbit and monkey eyes, but not for the human eye due to ethical reasons. In the present study, the temperature elevation in the lens, the skin around the eye and the core temperature of numerical human and rabbit models for far-field and near-field exposures at 2.45 GHz are investigated. The temperature elevations in the human and rabbit models were compared with the threshold temperatures for inducing cataracts, thermal pain in the skin and reversible health effects such as heat exhaustion or heat stroke. For plane-wave exposure, the core temperature elevation is shown to be essential both in the human and in the rabbit models as suggested in the international guidelines and standards. For localised exposure of the human eye, the temperature elevation of the skin was essential, and the lens temperature did not reach its threshold for thermal pain. On the other hand, the lens temperature elevation was found to be dominant for the rabbit eye.

Change in retinal image contrast with age in eyes with transparent lenses.

PURPOSE: To compare and evaluate changes in the retinal image with age in Japanese adults with transparent crystalline lenses. SETTING: Shibuya‐ku, Tokyo, Japan. DESIGN: Cross‐sectional study. METHODS: The study comprised right eyes with corrected distance visual acuity better than 0.0 logMAR. A point‐spread function analyzer (PSF‐1000) was used to measure retinal image contrast with 3.0 mm pupils under maximum mydriasis. A wavefront analyzer (KR9000PW) was used to measure higher‐order aberrations (HOAs) with 4.0 mm pupils. The lens transparency property was estimated by the backward light‐scattering intensity of each layer of the lens and the optical distance (mm) photographed by an anterior segment analysis system (EAS‐1000). The Pearson product‐moment correlation (R2) was used for statistical analysis; the significance level was 5%. RESULTS: The study comprised 269 patients (mean age 39.7 years ± 7.7 [SD]). The retinal image contrast degenerated significantly with age; the largest difference was seen with the 0.423 logMAR optotype, for which the decrease was 5.4% every decade. Backward light‐scattering intensity (R2 = 0.030, P<.01) and HOAs (R2 = 0.032, P<.01) correlated negatively with retinal image contrast. CONCLUSION: Retinal image contrast in eyes with transparent lenses degenerated with age. The decrease was most prominent at the middle frequency domain and was due to the increase in HOAs and light‐scattering intensity. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

An investigation of the heat transport mechanism under the millimeter-wave exposure considering the convection in the anterior chamber of rabbit's eye

The experiment exposing the millimeter-wave (MMWs) is performed to investigate the relation between the temperature elevation at the ocular tissue and MMW exposure. The temperature and velocity distributions in front part of the eye are simultaneously measured by using Micro-Encapsulated Thermo-chromic Liquid Crystal and Fluoroptic Thermometer. It is found that the flowing patterns of aqueous humor depend on the incident power density, and these patterns affect the heat transport mechanism.