Most wearers are unaware that a contact lens prescription and an eyeglass prescription are not necessarily the same. Apparently, they don’t understand their own prescription. They get an eye exam and buy glasses wherever they get an eye exam. They could buy men’s, women’s and children’s glasses online and buy anti-glare glasses from other sources such as online glasses stores, but that would need the buyer to know the detailed description of their eye power. Also, if you need to buy contact lenses, you need to know how to convert them.
With Eyeglasses, it is also essential to keep all the necessary technical factors in place. The measurement of PD (pupillary distance) is important. It is measured as the distance between the two pupils. It can be measured with a simple scale and a mirror in front. It is measured in millimeters. If you notice a number like 62/59 written on a prescription, that would mean that the range DP is 62 while the close DP is 59.
The PD distance is measured by looking straight ahead and the PD reading is measured by looking closely. Each eye, when measured individually, is called MPD, which is monocular PD. There is not much variation in adult PD that occurs over time. Correct PD measurement helps ensure precision in eyeglass manufacturing. If one intends to buy glasses online, then this measure helps.
We can also convert an eyeglass prescription to a contact lens prescription, but not the other way around. This is because there could be a cylindrical power involved in the prescription that can be converted to the contact lens prescription. However, with a contact lens prescription, it’s hard to know what the glasses prescription might be. Some good online stores have a conversion chart to convert the power of glasses to the power of contact lenses.
You should also know how to read an eyeglass prescription. Once the wearer receives a prescription for eyeglasses from their doctor, after having done a complete refraction to find out if there is any refractive error of the eyes, they can think about wearing contact lenses depending on the power of the eyeglass.
Glasses prescription has some abbreviated forms like OD and OS, which stands for Oculus Dexter and Oculus Sinister. In simple words, it is right and left. These numbers are either positive or negative, indicating farsightedness or nearsightedness. Positive indicates that the person is farsighted, while negative indicates myopia. Ideally, if one knows the complete spherical, cylindrical, and axis of each eye, then one knows that they are myopic, farsighted, or have astigmatism. However, a full prescription could also include astigmatic features.
In addition to the two measurements given on the prescription, for astigmatism, there must also be an axis. The axis is between zero and one hundred and eighty. The axis gives you the location of the astigmatism. The greater the cylindrical power, the greater the astigmatism.
A prescription can also consist of prism power. This occurs rarely and could indicate diplopia. Whenever there is prismatic power, they have a direction or a base. This feature can be up, down, in, or out.
Whenever there is a prescription with an Add power written at the end that would always be a positive number, this would indicate a bifocal or progressive lens prescription. Positive power is the amount of extra concentration needed to aid in reading.
However, with contact lenses, there is more involved. One must be able to convert the power of glasses or spectacles into contact lens power or seek professional help for the same. Depending on the type of lenses to be used, the prescription and adaptation of contact lenses involves much more than the adaptation of lenses for glasses. There are a different variety of lenses available such as hard lenses, semi-soft lenses, and soft lenses.
Soft lenses are available in annual, monthly, and daily lenses.
It makes a lot of sense to buy glasses and contact lenses online. Getting your eyeglass prescription from your eye care professional and ordering glasses and contact lenses online saves you money and time.