Testing of aspheric lens
The optical axis of the optical center just overlaps with the visual axis of the eye, which is the most ideal state. Because the light from the edge cannot form a focus on the optical axis, when the optical axis does not overlap with the visual axis (the difference is greater than 2mm), such unclear and scattered imaging results will occur. When choosing frames and aspheric lenses, you need to ensure that they fit correctly, to achieve the best visual and decorative effects. Simply put, due to the special design of the lens, we found through a calculation that the optical center should move down 1mm higher than the pupil for every 2° increase in front inclination angle. Otherwise, the wrong pupil height will cause the lens to look like astigmatism, and cause discomfort. For glasses with aspheric lenses, there must be an inclination angle after wearing. The specific angle varies from person to person.
The Cons of Progressive Lenses
In this section, we will show you the cons of progressive lenses. There are some problems with progressive lenses especially when walking up and downstairs. Since the reading correction is at the bottom, the stairs may appear closer than they actually are. But this problem can disappear if you have adapted to them.
In addition, all measurements must be exact when creating a pair of progressive glasses. The optical center of the lenses must be placed exactly in front of your pupils in order to the lenses to work correctly.
Also, some people may find that it is difficult to adapt the progressive lenses, and it may take a few days to adapt them.
These are the progressive glasses’ pros and cons. If you want to a pair of progressive glasses, Koalaeye glasses are recommended. Koalaeye glasses are stylish and come at a cheap price. Besides progressive glasses, Koalaeye Optical also provides other eyeglasses, such as blue light block glasses, polarized glasses, sunglasses, and so on. So, if you need a pair of progressive glasses, try Koalaeye glasses.
How to Choose Reading Glasses?
If you need reading glasses when using a computer, you may want to choose a lower reading glasses power. This is because most people view their screen from a greater distance from their eyes than when they are reading a book or a magazine.
However, if you need reading glasses for looking at something very close or very small, you may need a pair of stronger power glasses.
In most cases, when two reading glasses’ powers seem equally suitable, choose the glasses with the lower power. Picking reading glasses that are too string typically will cause more discomfort problems than reading glasses that are a little too weak.
Are prescription glasses bought online safe?
You can buy good-quality prescription glasses from online stores of major brands. Like Essilor Official Flagship Store, Baodao Optical Official Flagship Store, these brand stores have professional processing and customer service teams behind them, and the quality of the processed glasses is very good. There are basically no counterfeit sales of brand lenses and frames. SelectSpecs.com sells high-quality prescription eyeglasses to thousands of new and existing customers each year. They are always committed to providing our customers with high-quality products at very competitive prices. SelectSpecs.com provides the lens coating free of charge. Specialist eyewear brands like EyeBuyDirect also offer high-quality prescription eyewear.
How Should Glasses Fit?
You should check the placement of the bridge. The bridge is the small middle piece on the front of your frames that sits on your nose. This measurement is usually the middle number displayed on the inside of your temple. The bridge should rest comfortably on your nose without pinching or sliding off. A correctly fit bridge will also ensure your glasses sit properly on your face and your eyes are aligned appropriately within your lenses.
How should glasses fit? You need to consider the size of your lenses, which is essential to the proper function of your prescription, especially with the progressive lenses, because it ensures that there is enough space for the near, intermediate and distance zone powers of your prescription.
Parameters of lens material selection
Abbe number
Since the refractive index of the lens material varies for the light of different wavelengths, and white light is made up of various colors of light of different wavelengths, the dispersion phenomenon occurs when the lens refracts white light. The dispersion coefficient is an important index to identify the sharpness of lens imaging, which is usually indicated by Abbe number (Abbe number = dispersion coefficient). The larger the Abbe number, the smaller the dispersion, and vice versa, the smaller the Abbe number, the larger the dispersion, and the worse the resolution of the image.
Impact resistance
Humans have been using glass lenses for about 300 years, and it was not until 1947 that the first resin lenses made of CR39 were produced. A big reason for using resin lenses is their safety, i.e. impact resistance. Only lenses that pass the Drop Ball Test are considered safe. Combining the above two parameters, we can compare different lenses.
Online stores have fewer customer service staff and low human resources costs.
Generally speaking, to choose the website shopping, you can directly click on the website, and then get professional customer service reception. The data for each customer visit is accurate. The online stores just need to solve the customer's needs, so the customer service staff is relatively small in numbers, and the human resources investment is relatively small. So the price of glasses will be lower for each customer. Brick-and-mortar stores focus on service. Online shops is involved in the whole network competition, and the entity store is service first. The advantage of physical stores is very obvious,because they can provide perfect service. So the physical store manpower cost will increase.
