Most users are not aware that the contact lens prescription and the eyeglass prescription are not necessarily the same. Apparently, they don’t understand their own prescription. They get an eye examination done and buy glasses from where ever they get the eye exam. They could buy eyeglasses online for men, women and kids and buy antiglare glasses from other sources such as online eyewear stores but that would need the buyer to know the detailed description of his eye power. Besides if he needs to buy contact lenses, he has to know how to convert the same.
With Eyeglasses, it is also essential to keep all required technical factors in place. The PD (Pupillary distance) measurement 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 figure like 62/59 written on a prescription, then that would mean distance PD is 62 while the near PD is 59.
Distance PD is measured by looking straight and reading PD is measured when looking close. Each eye when measured individually is called MPD which is monocular PD. There is not much variation in the adult PD that takes place with time. The correct PD measurement helps in ensuring accuracy towards making of eyeglasses. If one intends to buy eyeglasses online, then this measurement helps.
We can also convert an eyeglass prescription into a contact lens prescription but not the other way around. This is because there could be a cylindrical power involved in the prescription which can be converted to the contact lens prescription. However, with the contact lens prescription, it is hard to know what the eyeglass prescription can be. Some good online stores have a convertor chart to convert spectacle power to contact lens power.
One should also be aware of how to read an eyeglass prescription. Once the user receives an eyeglass prescription from his doctor, after he has done a complete refraction to find out if there are any refractive errors of the eyes, he may think of using contact lenses depending on the eyeglass power.
Eyeglass prescription has a some abbreviated forms like OD and OS which means Oculus Dexter and Oculus Sinister. In simple words, its Right and Left. These number are either positive or negative indicating farsightedness or shortsightedness. The positive indicates the person is farsighted while a negative indicates nearsightedness. Ideally, if one knows the complete spherical, cylindrical and axis for each eye, then he knows that he is nearsighted, farsighted or has astigmatism. However, a complete prescription could also include astigmatic features.
Other than the two measurements given on the prescription, for astigmatism, there needs to be the axis as well. The axis is between zero to one hundred and eighty. The axis gives you the location of the astigmatism. The higher the cylindrical power, higher is the astigmatism.
A prescription may 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 could be up, down, in or out.
Whenever, there is a prescription with an Add power written at the end which would always be a positive number, this would indicate a bifocal or a progressive lens prescription. The positive power is the amount of extra focussing needed to assist in reading.
However, with contact lenses, there is more that is involved. One should be able to convert the eyeglass or spectacle power to contact lens power or seek professional help for the same. Depending on the type of lenses to be used, the prescription and fitting of contact lenses involves a lot more than fitting for spectacle lenses. There are different variety of lenses available like hard lenses, semi-soft lenses and soft lenses.
Soft lenses are available in yearly, monthly and daily lenses.
There is lot of sense to buy eyeglasses and contact lenses online. Getting your eyeglass prescription from your eyecare practitioner and ordering eyeglasses and contact lenses online saves you money and time.