Why Frame Degree and Contact Lens Degree are Not the Same?
Contact Lens Degree Conversion Table:
Contact lens diopter = glasses diopter/(1-0.012* glasses diopter).The diopter of myopia is negative, and one diopter is equivalent to what we usually call 100 degrees.
If your eye is already above 400 degrees, the contact lens you bought will need to be converted based on accurate optometry.But if you have an eye degree below 400 degrees, the formula translates to a contact lens degree that is close to that of a frame and negligible.
Warm tips: If the wearing of contact lenses is not accurate, it will often lead to visual difficulties, increase the burden of the eye, may affect the long-term vision of further decline.Before buying contact lenses, it is best to pass a special optometry, so as to better enjoy contact lenses.
How does contact lens degree choose
A lot of myopic patient thinks, the degree that matchs contact lens to use frame glasses directly matchs can, this kind of practice is wrong, the degree of contact lens and frame glasses are different.So, how does this contact lens degree get?This requires a professional to go through the vertex diopter conversion.
Usually, the diopter obtained by optometry is the degree of the glasses. There is a distance of about 10-15mm between the glasses and the cornea, while the contact lens is in direct contact with the cornea. Due to this distance difference, the diopter required by contact lenses is different from that required by the glasses.
The formula of contact lens degree conversion is: Fc=Fs/(1-d×Fs).
In the formula, Fc is the diopter of contact lens, Fs is the diopter of frame glasses, and D is the distance between frame lens and cornea (the distance of yellow race is generally 12mm, or 0.012m).
Assuming that the prescription of a frame glasses is -4.00d and the vertex distance of the lens is 12mm, the degree of contact lenses is: -4.00/[1-0.012×(-4.00)]= -3.82d.
Notics:For high astigmatism, or the degree of astigmatism is not mainly caused by the cornea (namely, in the eye astigmatism) patients, the need to order a special astigmatism contact lens, including soft astigmatism contact lens and hard permeability astigmatism contact lens.
Contact lens is a medical device. It should be worn according to the examination of an ophthalmologist, after excluding the discomfort certificate of the wearer, a professional contact lens examiner. It should be carefully evaluated in combination with the patient's eye habits, and it should be worn under the supervision and guidance of a optometrist.
Thank you
Mike Optical Company-Cayla
017@mikeeyewear.com
29.12.2020
