Research projects

Based on epidemiologic data showing that violet light (VL) exposure suppresses the myopia progression, we hypothesized that the nonvisual opsin OPN5, which has an absorption peak at wavelengths between 360 and 400 nm, is involved in myopia progression. Using a method developed in our laboratory to efficiently induce myopia in mice by fitting them with -30D lenses, we showed that VL irradiation suppresses myopia progression and that OPN5 is involved in this suppressive effect in experiments using OPN5 knockout mice. We also searched for drugs and foods that inhibit myopia progression, and found that the glaucoma drug bunazosin and foods such as ginkgo extract were effective.

Epidemiological studies were conducted in Tokyo and Brazil to understand the prevalence of myopia in modern school children. The prevalence of myopia/high myopia in Tokyo was 76.5%/4.0% in elementary school students, 94.9%/11.3% in junior high school students (E Yotsukura E, Torii H, et al. JAMA Ophthalmology. 2019). Furthermore, in Brazil, the prevalence of myopia and the light environment were investigated, and the prevalence of myopia/high myopia in school children was 20.4%/0.48%. It is reported that not only racial differences but also differences in light environment may affect the prevalence of myopia (Yotsukura E, Torii H, et al. J Clin Med. 2020).

The db/db mice were the animal model for a rodent model of type 2 diabetes. We investigated the molecular mechanism of tear secretion and metabolic changes. We used db/db mice and their non-diabetic db/m mice in all experiments. Measurement of tear secretion was performed once a month with a phenol red thread. It was placed on the temporal side of the lower eyelid margin for 30 seconds. After measurement, the mice were sacrificed, lacrimal gland extirpated and lacrimal gland were used all experiments. Serum samples were collected for biochemical analysis. Body weight of db/db mice were significantly increased than db/m mice. In the biochemical analysis of the serum, blood glucoce were significantly higher in the db/db group than in the db/m. At the 3-month time-point of the experiment, tear secretion was decreased by the db/db mice compared to the db/m mice. We concluded those energy metabolism genes are key molecules for tear secretion.

We focused on violet light (VL, 360～400 nm wavelength), which is abundant in outdoor environments, and carried out research using a chick myopia model. Through that model, myopic progression of chicks exposed to VL was suppressed, and early growth response 1 (EGR1) was confirmed to be upregulated in chicks exposed to VL. In addition, the research also suggests that those wearing contact lenses that transmit VL suppress myopia progression more than those wearing contact lenses or glasses that do not transmit VL, suggesting that myopia progresses when wearing glasses that do not transmit VL. Furthermore, the LEDs and fluorescent lamps often used today contain little VL, and it was found that VL does not pass through materials such as the UV-protected eyeglasses and window glass. That is, in modern society there is a lack of VL, which may be related to the global increase in myopia.