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1. #SPECTACLE OPTOMETRY HOW TO#
2. #SPECTACLE OPTOMETRY FULL#
3. #SPECTACLE OPTOMETRY SOFTWARE#
4. #SPECTACLE OPTOMETRY PLUS#

#SPECTACLE OPTOMETRY HOW TO#

If your prescription doesn't have your PD on it, don’t worry, we have a tutorial that teaches you how to measure your PD yourself. PD: This number indicates the distance from the center of one pupil to the center of the other, and is an important number for lens customization. It may also be written as a large, positive number, across both the OD and OS lines of your prescription. It is typically the same positive number, for both eyes, although it may be written only once on your prescription.

Just have one ADD number on my prescription? That’s because for most people, ADD will be the same for both eyes. If you need reading, intermediate, bifocal or multifocal, or progressive lenses, this should be listed in your prescription. From 1 to 180 degrees.ĪDD is an additional strength for your lens for reading or upclose work. The AXIS represents the orientation or angle of your astigmatism. The higher the number, the more astigmatism you have.

CYL or cylinder is the degree of how flat your eye is. Astigmatism is where the eye is not completely spherical but shaped more like a football.

#SPECTACLE OPTOMETRY FULL#

If you have astigmatism, CYL and AXIS will be full in your prescription. The larger the number, the stronger the prescription you needed to correct your vision.

#SPECTACLE OPTOMETRY PLUS#

There will be a plus sign for farsighted and negative sign for nearsighted - followed by a number. This indicates the amount of lens strength. SPH stands for sphere or spherical power. OD means 'right eye' and OS means 'left eye'. Doctors use this to tell you that you need single vision lens instead of bifocal or progressive lens. Doctors usually use this to distinguish different usage. NV stands for near vision for reading use or computer use.ĭV stands for distance vision for constant wear or daily use. Let's take a moment to decipher and understand what’s on your prescription. It makes ordering prescription glasses online challenging and overwhelming.

#SPECTACLE OPTOMETRY SOFTWARE#

In the case of optimised prescription surfaces, on-board software will analyse the result by ray tracing to obtain the final z-co-ordinates.Īberrations aspherical surfaces atoroidal surfaces oblique astigmatism power error.When you leave your eye doctor's office and look at your prescription, it may seem like an unrecognizable series of numbers and abbreviations. In the case of free-form progressive surfaces, the pre-determined z-co-ordinates must be added to the z-co-ordinates of the prescription surface to obtain the final free-form surface. Examples of how these co-ordinates can be obtained from the equation to the surface are given for toroidal and aspherical surfaces. The advent of free-form manufacturing techniques requires the lens designer to convert the surface description to the (x,y,z) co-ordinates needed to generate the surface. In the case of astigmatic prescriptions, the surface requires different asphericities along its principal meridians and the geometry of these atoroidal surfaces is also described. The various types of aspherical surface and how the surface astigmatism arises is described, before considering how this feature is used to produce flatter, thinner lenses. Aspherical surfaces are employed because the surface itself is astigmatic and the surface astigmatism is used to combat aberrational astigmatism due to oblique incidence. Today, aspherical surfaces are used by all major lens manufacturers to produce thinner, lighter and more attractive best-form lenses in the normal power range. Before 1985, aspherical surfaces were used only for post-cataract spectacle lenses and high-power magnifiers. A brief review of these aberrations is given, explaining how the lens designer can control them using just the bending of the lens, and what results can be achieved using simple spherical and toroidal surfaces. The most significant aberrations are oblique astigmatism and mean oblique error (power error). Ophthalmic lens design concerns the control of spectacle lens aberrations which occur when the eye rotates away from the optical centre of the lens.