Why is a prescription for glasses different from a prescription for contact lenses?
The frame glasses degrees are the optometric degrees of the eye, and the difference between the frame glasses degrees and the contact lens degrees is mainly due to the different contact distances between the two lenses and the eye. Usually, degrees of contact lenses and glasses need to be converted by a professional through vertex diopter. The conversion formula is Fc=Fs/(1-d×Fs). In the formula, Fc is the diopter of contact lens, Fs is the diopter of glasses frame lens, and D is the distance between frame glasses lens and cornea. Assuming that the prescription of frame glasses is -4.00d and the distance between lens apex is 12mm, the prescription of contact lenses is -4.00/ [1-0.012×(-4.00)] = -3.82d.
Do not wear blue light blocking glasses for a long time.
Blue light from the screen of electronic products directly enters our eyes. It has high energy and is close to our eyes, so it is more harmful to our eyes. This is why we should prevent electronic products. From the original intention of the blue light glasses, blue light glasses are for us to wear when using electronic products, not all day long. Therefore, if your child is not using electronic devices, it is recommended not to wear blue light glasses.
Can You Wear Glasses Without Prescription?
So, can you wear glasses without prescription? Of course, you can. You can wear glasses without prescription and they would not cause any damage to your eyes. What’s more, some non-prescription glasses, such as the type that blocks harmful blue light, can be beneficial to your eyes.
What is hard coating on lenses?
Lenses are mainly added in two kinds of film: anti-reflection film and hard film (and some manufacturers produce anti-fogging film and mirror film, but not common). The anti-reflective film is mainly by coating the front surface of the lens with multiple layers of transparent materials with different refractive index and thickness to reduce the excess reflected light on the surface of the lens, by using the principle of light interference. The film can be applied to both glass and resin lenses. The way of hard film plating is usually a soaking process. After many times of soaking and cleaning, soaking in an organic solution containing ultrafine silicon element for a certain time, and then keeping it at a certain temperature for 4-5 hours, the fixed polymerization process of the film has been completed. The surface wear resistance of CR-39 coating can be increased by 2-4 pH, which is similar to the hardness of optical glass lenses.
