![]() ![]() This eye condition is referred to as an astigmatism. When your eye has this condition we need to add cylinder to correct for the irregular shape of the eye. There may be instances where we can provide guidance on the frame selected and your lens requirements if you give us a call or contact us via email.Ĭylinder or CYL – When your eye is not exactly spherical the light doesn’t focus exactly where needed for optimal vision. We don’t suggest semi rimless or rimless frame designs because the lens is thinnest on the edges and these designs may not provide sufficient material where the lens is anchored to the frame. Choose frames with smaller lens openings, narrower widths, and consider buying higher index plastic for your lenses. To help minimize the effect the techniques suggested to reduce edge thickness can work to minimize the center thickness for farsighted lenses. In cases of positive sphere values the center of the lens will tend to magnify the eye and some find this unappealing. In this case the far vision is better than the near vision. As the power of the lens increases the edge thickness gets thicker so if the aesthetic appearance of the lens edge concerns you we suggest selecting frames with smaller lenses, narrower lenses, buying frames with rounder lens openings, and buying higher index plastic lenses to help reduce the edge profile.Ī positive sphere (sphere value preceded with a plus sign) means that you are farsighted and the lens is thickest in the center of the lens. Typically the nearsighted lens is thinnest in the center and thickest at the edges in order to bend the light for optimal correction. A majority of corrective lenses made correct for nearsightedness. This means you have better near vision than you have the ability to see distant images. Sphere - SPH – Sphere or Spherical - Provides the depth of the focal field in the lens.Ī minus sphere (sphere value preceded by a minus sign) means you are myopic or near sighted. ![]() The smaller number would be used only when converting the prescription to single vision reading glasses and multifocal lenses. This would mean that you use 63 as your PD for distance vision. You might be given two numbers such as 63/60. Most adults have a PD between 53 and 70, and children will be between 41-55. If your PD value is expressed as 63/60, the first number if the PD for distance vision and the second number is called the near PD for reading or near activities. We use an average 58 mm PD for women and an average PD value for men of 63 mm. Because children grow PD values can range average over a wide area from 36 mm to 56 mm with the lowest values for toddlers and the higher values for teens. We know through tens of thousands of patients that adults have PD values between 50 and 70 mm. With your PD you are able to purchase eyeglasses from any source and not just the place where your exam was performed. In the end we want you to be satisfied with the quality and accuracy of your lenses and the PD value is crucial to this goal. There are many ways to obtain your PD if your practitioner is unable or unwilling to provide these measurements so check other resources on the site for how you might be able to help yourself. The PD value helps us adjust the various fields of view in your multifocal lenses to the optimal position when the PD measurements are accurate. If you so choose we will use an average PD value to manufacture you eyeglasses lenses.īecause there are many variable points of focus in a multifocal lenses – such as bifocal or progressive lenses – the need for an accurate PD is even more important. We cannot make your corrective lenses without a PD value. That is why two PD measurements are best. ![]() This measurement is used to position the optical correction in the lens directly in front of the pupil for each eye. A measurement with OD and OS PD values is a measurement to each pupil centerline from the center of the bridge (nose) area. A single PD number is a measurement of the distance between the centerline of your pupils and it is measured in millimeters (mm). The best and most accurate PD measurements are when you have two measurements (right-OD and left-OS) since no one is exactly symmetrical on the right and left side of their bridge. At the time of your optical examination you can ask the person doing the exam to measure your PD. You should also know that a contact lens prescription cannot be used to make eyeglasses.Įye examinations do not necessarily result in a PD measurement but proper manufacturing of your lenses will require an accurate PD value, either one measurement, or two. You will also need to have your pupillary distance (PD). Unless you are buying frame only or frames with plano (no Rx lenses), you will need a prescription to place an order for corrective eyeglass lenses. ![]()
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