How to calculate the power of reading glasses
How to calculate the power of reading glasses
Reading glasses are a tool used by most older people to aid their vision. However, many elderly people do not have a clear concept of reading glasses and do not know when to wear reading glasses. So today, I will bring you an introduction to the calculation method of reading glasses, let's learn together. Reading glasses prescription calculation method Reading glasses have a prescription, the prescription of reading glasses will increase with age, generally after the age of 60, the prescription of the eyes will not change much. The change of prescription is also regular, generally it increases by 50 degrees every five years, in the case of good eyes, there is no other situation, generally 45-year-old eye presbyopia power is 100 degrees, 55-year-old is 200 degrees, in 60 years old, it reaches 250 degrees to 300 degrees, and the glasses power will not deepen in the future. So how should the degree be calculated? Equipment used: Scale, cardboard, sunlight. Operation steps: 1. Make the reading glasses perpendicular to the mirror, and put cardboard on the other side. 2. Repeatedly adjust the distance from the cardboard to the mirror surface until the smallest bright spot appears on the cardboard. 3. Use a scale to measure the distance f (in meters) from the bright spot to the center of the mirror. It's its focal length. 4. Use the power of reading glasses equal to the reciprocal of its focal length multiplied by 100 to calculate the power of reading glasses. Reading glasses prescription is age-related. For example, at the age of 45, presbyopia is +1.50D (i.e., 150 degrees), and at the age of 50, whether you wear glasses or not, presbyopia will increase to +2.00D (i.e., 200 degrees). If you have already seen presbyopia, if you don't wear reading glasses, you will not be able to adjust the exhaustion of the ciliary muscles, which will definitely aggravate reading difficulties, produce dizziness and swelling and many other symptoms, and affect life and work, which is very unwise. So, reading glasses should be fitted immediately, don't delay. As you get older, the prescription of your reading glasses is not enough, so you need to replace them in time. Therefore, if the elderly want to wear progressive lenses, they should choose carefully. According to the advice of the internal staff of a brand optical store, the general eye adaptation cycle is usually one to three weeks, and if they still can't adapt, they will recommend that the elderly change back to single-lens reading glasses. If you wear glasses with inappropriate prescription for a long time, it will not only bring a lot of inconvenience to the life of the elderly, but also accelerate the aging of the elderly's eyes. And if you find that you have presbyopia, you don't need to wear reading glasses right away. Older people should be given enough opportunities to exercise their eyes while their ability to adjust their vision is still alive.