What Are Pinhole Glasses?
Pinhole glasses, also called stenopeic glasses, are plastic eyewear with hundreds of pinhole-sized perforations in place of lenses. Pinhole glasses are mostly used to improve refractive errors in the eye because they shield the eye from indirect rays of light which can distort vision. This would decrease the blur circle on the back of the retina.
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.
Titanium frame machining is complicated.
The elastic modulus of titanium alloy is small, which is easy to produce large deformation, springback, distortion, and vibration in cutting, resulting in poor geometric shape and accuracy of the workpiece. As the surface roughness increases, the tool wear increases. The thermal conductivity of titanium alloy is poor and its thermal conductivity is small, 1/6 of that of 45 steel, so the high heat generated in processing cannot be effectively diffused. It is even harder to use titanium to make glasses. The frames are very thin and a lot of fine work is demanded. It's definitely a challenge for titanium, which is pretty difficult to work with. In addition, titanium alloy frames involve titanium alloy welding technology, which is more difficult.
How much do a pure titanium eyeglass frame cost?
What’s the probable price of a a pure titanium frame? The price is not the same, due to customer demand. There are pure titanium frames, Beta titanium frames, and half titanium frames. Online shopping is different from physical stores, and online shopping prices are probably only more than 50% of the physical optical stores. The price of the pure titanium frame is more expensive, be in 500 above commonly. The frame of pure titanium appears sedate mature, suiting the man with a successful career quiet. The price of a titanium frame is relatively cheap, usually around 300. The titanium alloy frame is practical and suitable for students. Prices vary depending on the brand, style, material, and even location of the frame. The price of the eyeglass frame is determined by several aspects, like the brand material, the marketing mode, and so on.
Is there a standard for lens material selection?
No, again, according to your needs and budget. The materials of lens mainly include glass and resin, among which resin materials are divided into thermoplastic materials and thermosetting materials, respectively represented by PC and CR39. Different from the lens frame, the lens market choice is more uniform. And in recent years, resin lenses do better and better, most people choose thermosetting resin lenses.
Buy Prescription Glasses Online Step By Step
1. Before you can buy glasses online, you’ll need a current glasses prescription.
2. Select an online retailer, comparing online retailers like EyeBuyDirect and KOALAEYE until you find the best fit for your needs.
3. Shop for the perfect frames according to face shape, frame favorites, the budget, etc.
4. Once you’ve found your perfect frames, you’ll enter your eyeglasses prescription and pupillary distance to choose the lenses.
5. Read over the fine print on return/exchange policies and product warranties before you complete your order.
6. Having picked your perfect frames, entered your prescription information, added any lens coatings and upgrades, and checked your online retailer's warranty and return policy, it’s time to complete your order.
The disadvantages of progressive lenses
- The field of view in the near and middle distances is relatively narrow.
- The adaptation time is longer and patients with greater astigmatism are not suitable for wearing.
- The peripheral aberration is large, and there will be large astigmatism in the periphery.
