gradual multifocal spectaclesThe lenses were developed by Bernard Maitenaz, a Frenchman, after eight years of research and development. They were first used in actual products in 1959.
The design principle was to seamlessly connect the far-sighted area and the near-sighted area on the same lens through the gradual change of refraction, so that the same lens could simultaneously have the function of viewing a variety of different luminosity required for long distance, medium distance and close distance. It is suitable for people of all ages, especially those whose myopes do not exceed-10.00D and whose aberrations are less than-2.00D.
In terms of usage, it could be simply worn. One pair could replace the traditional three pairs of glasses and help prevent further deterioration of vision. However, eye discomfort may occur when using it for the first time, such as eye soreness, fatigue, or mild dizziness. Usually, it can be relieved within a few days. Users with diseases such as epilepsy, eyeball trauma, acute eye diseases, and high blood pressure should avoid using it.
From the optical center of the lens, it was much more complicated than the single-focus (near-vision, far-vision) lens. It required data such as the reference circle, the cross, the prism reference point, the reference circle, and the left and right lenses were different. Among them, the cross of the glasses corresponds to the customer's pupil, the distance reference circle is located 4mm above the cross of the glasses to measure the distance refraction, the prism reference point is located 4mm below the cross of the glasses to accurately measure the actual prism power of the lens, and the near reference circle is located below the prism reference point, which is the most accurate place to measure the near power and ADD.
In terms of focal point distribution, a single-focal lens only had one focal point, which could only see far or near. Although a bifocal lens and a three-focal lens could see far and near, the focal points were distributed in different positions, and the difference was large. Wearing it would cause situations such as jumping, dizziness, headache, eye pain, etc., while a gradually changing focal lens was connected by many focal points with small differences. According to the reasonable distribution of the four different areas, it could see far and near, and there would be no problems wearing a bifocal lens or a three-focal lens.
When choosing the frame, the height of the mirror ring should meet the distance field of view and the near field of view. The frame of the nose pad should be selected. After adjustment, the distance between the eyes should not exceed 12mm to obtain a better near-sighted field of view. The material structure of the frame should be firm and not easily deformed to avoid wearing discomfort caused by the frame distortion.
<a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
What is 'les sept jours du talion english novel' about?2 answers
2024-11-05 20:17
Since I don't have detailed information about this 'les sept jours du talion english novel', it's hard to say precisely. However, if we break down the title, 'les sept jours' means 'the seven days' and 'du talion' might imply a theme of retribution or getting even. Maybe it's a mystery or thriller novel where events occur within a week and are centered around a revenge - based plot.
Superbe histoire hâte De voir la suite. Et voir où les jumeaux sont prêt à aller dans leur vendetta