Anthony Lee - Oct 13 2022
What is Cyl, Axis, and Sph?
The accuracy of the optometry is directly related to the success rate of the prescription glasses. If the optometry is inaccurate, the glasses will have blurred vision, visual fatigue, dizziness, nausea, and even double vision. Computerized optometry is currently the most familiar optometry method, which uses optical focusing to measure the specific degree. However, the mechanical reading of the data does not take into account the subjective feelings of the human eye, so computerized optometry is only one of the initial stages of medical optometry.
Medical optometry begins with an eye health examination, and for patients with visual fatigue, a binocular vision function examination must also be performed, and for children's optometry or the first glasses prescription, dilated pupil optometry must be used.
A Simple Explanation of the Terminology
Pupillary distance (PD)
The horizontal distance between two points in the center of the pupil of the left and right eyes, generally the PD on the optometry form without special remarks means the distance pupil distance of both eyes. Generally, the abbreviation "PD" is used to indicate the unit of millimeter (mm).
Spherical lens (SPH)
Nearsightedness, farsightedness and presbyopia. SPH is "-", indicating myopia; SPH is "+", indicating farsightedness or presbyopia. Spherical lenses have concave and convex lenses, concave lenses are indicated by the "-" sign to correct nearsightedness; convex lenses are indicated by "+"; to correct farsightedness.
Columnar lens (CYL)
The degree of astigmatism.
Axial position (AXIS)
The direction of astigmatism. Note: Astigmatism axial position only with astigmatism; without astigmatism, no axial position.
Corrected visual acuity (VA)
Refers to the visual acuity detected after wearing glasses.
Prescription example
If the prescription: +2.00DS_-2.00DC×90°
Then it means: Spherical lens Columnar lens Axial.
About lenses
Lenses are an important part of eyeglasses, and choosing a proper lens can be a good protection for your eyes.
01 Lens material
✏ Glass lenses Glass lenses are more scratch-resistant than other materials, but they are relatively heavy, fragile and unsafe, so they are rarely used.
✏ Polymer resin lenses Resin lenses are lighter and more impact resistant than glass lenses.
They can be divided into two types: spherical resin lenses and aspheric resin lenses. Resin lenses are popular among consumers for their UV protection, radiation protection, lightness, and high safety. Super tough lenses The lenses have a patent of independent research and development, patent number: CN101241238B.
The impact resistance is 5.6 times higher than the national standard and safer. The lenses are clearer and more comfortable with excellent imaging quality. It is the first choice for teenagers to get glasses.
02 Refractive index of lenses
The refractive index of lenses reflects the degree of refraction of light by the lens material, which is different from the transmittance. Usually, 1.49 and 1.501 refractive index lenses are ordinary lenses, 1.56 and 1.60 refractive index lenses are light lenses, and 1.61 refractive index and above are ultra-thin lenses.
03 Lens film layer
By silicifying the inner and outer surfaces of the lenses, a thermochemical and mechanical protective layer is formed on the inner and outer surfaces of the lenses to increase the corrosion resistance and anti-friction properties of the resin material, which is the hardening film layer. In addition, coated lenses can selectively increase the transmission of visible light, improve the light transmission of the lenses, make the imaging clearer, also block harmful infrared and ultraviolet rays, and greatly improve the surface hardness of optical resin lenses.
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Anthony Lee
freelance writer
Written by: Anthony Lee
Anthony Lee is a freelance writer who works as a sales clerk in an eyewear boutique, and her seven years of experience allows her to select the right eyewear for her customers at a glance. Knowing the whole process of eyewear production, she also has a unique perspective on eyewear fashion. She is passionate about fashion accessories and life. She likes to match a variety of eyewear with various styles of clothing.
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