Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Ophthalmic lenses or blanks
Patent
1987-04-23
1988-11-08
Corbin, John K.
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Ophthalmic lenses or blanks
350438, 351163, 252582, 252589, G02B 520, G02C 710
Patent
active
047831421
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a radiation protection filter for skin pigmentation during solar irradiation.
For medical reasons, it is necessary to occasionally expose the skin of the human body to natural solar irradiation. The pigmentation resulting from the effect of certain spectral ranges not only provides an attractively tanned appearance corresponding to today's cosmetic fashion trends, but also shields unprotected skin from hazardous solar radiation. The pigmentary infiltration of the skin thus, to a large degree, protects against erythema-effecting radiation with a wavelength of less than 320 nm.
In order to achieve skin tanning in the fastest, most agreeable and physiologically safe manner during solar irradiation or irradiation with artificial radiation sources, the applicant has already developed a radiation protection filter made of a plastic with an incorporated radiation-absorbing material (DE-OS No. 26 09 194). This radiation-absorbing material blocks any physiologically harmful radiation with a wavelength shorter than 320 nm, filters out radiation over 450 nm as much as possible, and provides the highest possible transmittance in the intermediate range.
Now, it is a known fact that, apart from acute inflammations after lengthy exposure, radiation with a wavelength shorter than 340 nm can also lead to irreversible dimness (cataracts) in the lens of the human eye. Recent studies have shown that radiation in the 340 to 400 nm range can also cause such eye damage. On the other hand, radiation in the 340 to 440 nm range can be used to achieve skin tanning with healthy persons without the risk of sunburn, skin cancer or premature skin ageing.
The object of the invention is thus to design a radiation protection filter for skin pigmentation during solar irradiation in such fashion that radiation-caused eye damage is avoided. Inasmuch as the radiation protection filter is used in the form of tanning eyeglasses, it is to be designed in such fashion that, on the one hand, the skin area covered by the glasses around the eyes will be sufficiently tanned, whereas, on the other hand, radiation-caused eye damage is prevented.
The object of the invention can be achieved by maintaining the following relationship between the radiation wavelength and the mean transmittance of the filter:
______________________________________ Wavelengths (nm)
Transmittance
______________________________________
300-340 0.1 maximum, more preferably
0.01, and most preferably
0.001
340-400 0.35-0.55
340-440 0.45-0.7
______________________________________
radiation in the wavelength range between 380 and 780 nm if the protection
filter's light transmittance is such that, when the filter is used, the
amount of radiation in the range between 340-400 nm that penetrates the
eye lens does not exceed that amount of radiation in the 340-400 nm range
which penetrates the eye lens when the filter is not used.
The inventive doctrine is based on the considerations described in the following. With regard to the symbols used therein, reference is made to the list of symbols at the end of the description.
The radiation penetrating the lens of the human eye is determined by the irradiance in the pupillary plane and by the pupillary surface area (i.e. the size of the pupil in the iris). The pupillary surface area, in turn, is regulated in the case of healthy persons of medium age by the illumination E.sub.vis in the pupillary plane. Since it is very difficult to measure the irradiance or illumination in the pupillary plane directly, the corresponding tangential values for the front side of the eye (cornea irradiance or cornea illumination) normal to the line of vision are used for calculation.
The invention proceeds from the assumption that the risk of lens damage (cataracts) from solar irradiation of the unprotected eye in the 340 to 400 nm range is tolerable for a healthy person. Proceeding from this assumption, the invention provides that, in the case of protected eyes (i.e. when the radiation protection filter is
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patent: 3887485 (1975-06-01), Neuroth
patent: 3909441 (1975-09-01), Ohyama et al.
patent: 4200360 (1980-04-01), Mutzhas
patent: 4238351 (1980-12-01), Alfes et al.
patent: 4643537 (1987-02-01), Vance
patent: 4674823 (1987-06-01), Epstein
Ben Loha
Corbin John K.
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