What Is a Diopter? Eyeglass Power Numbers Explained (-2.00, +1.50)
Quick answer: A diopter (D) is the unit of lens power. Minus numbers (for example -2.00) correct short-sightedness (myopia) and plus numbers (+1.50) correct long-sightedness (hyperopia) or near vision. The bigger the number, the stronger the lens: up to about ±3.00 is usually considered mild, ±3.00 to ±6.00 moderate, and above ±6.00 high. Cylinder and axis numbers correct astigmatism.
Noticed this in your own eyes? Book an eye examination (NPR 400) with an optometrist at Vision Concern Lazimpat, Boudha-Tushal or Makalbari. WhatsApp +977 9841466716.
Related service: Prescription glasses in Kathmandu at Vision Concern Lazimpat, Boudha-Tushal and Makalbari.
Reading the numbers
- SPH (sphere): the main power, minus for myopia, plus for hyperopia
- CYL (cylinder): extra power for astigmatism
- AXIS: the angle (0–180°) of the cylinder
- ADD: extra plus power for reading in bifocal or progressive lenses
- PD: the distance between your pupils, used to centre the lenses
Why high power matters for your lenses
Higher powers make lenses thicker and heavier. High-index materials (1.67, 1.74) make strong lenses thinner, and a smaller, well-fitted frame reduces edge thickness. Very high myopia also carries a higher risk of retinal problems, so regular eye health checks matter.
Glasses power vs contact lens power
Contact lens power can differ from glasses power, especially above about ±4.00, because the lens sits on the eye instead of in front of it. Contact lenses need their own fitting and prescription.
When to get urgent care
Get prompt care if vision changes suddenly, or if you notice flashes, a shower of floaters or a shadow in your vision, especially if you have high myopia.
How Vision Concern can help
Vision Concern optometrists in Kathmandu can examine your eyes, record what they find for comparison, update your glasses or contact lenses, and refer you to an ophthalmologist or eye hospital when medical treatment is needed. Vision Concern does not perform surgery or injections.
Frequently asked questions
Is -2.00 eyesight bad?
It is mild to moderate myopia. Distance vision is blurred without glasses, but it is very common and easily corrected.
What power is considered high?
Above about -6.00 or +6.00 is usually called high power.
Can I use my glasses prescription for contact lenses?
Not directly. Contact lenses need a separate fitting and prescription.
This guide is general information from the Vision Concern editorial team. It is not a diagnosis and does not replace an eye examination or medical advice.
Yes. Many visitors, particularly from Bangladesh and West Bengal (Kolkata), come to Nepal for cataract, retina, or other eye surgery at a hospital and also want new glasses, a general eye exam, or contact lenses at the same time, before or after their procedure. Vision Concern is an optical and eye-examination clinic, not a surgical hospital, so we work alongside hospitals such as Tilganga: we are happy to see you for glasses, contact lenses, or a routine check-up either side of your surgical treatment elsewhere.
No conversion is needed. Eyeglass prescriptions from Germany, France, the UK, the USA, China, Russia, and almost every other country use the same international format, SPH (sphere), CYL (cylinder), and AXIS, measured in diopters. Our opticians read this directly, so you can bring your prescription paper, a photo of it on your phone, or simply your current glasses, and we will use the same values. If your prescription is more than a year or two old, we recommend a quick, free re-check before we make your new pair.
Yes. Above roughly 3,000 metres, UV exposure increases sharply because of the thinner atmosphere and reflection off snow, and ordinary sunglasses (category 2-3) do not block enough UV to prevent snow blindness (photokeratitis). We recommend glacier glasses or category-4 sunglasses with side shields, and can fit these with your own prescription if needed. Vision Concern offers ZEISS polarized, UV400-certified sunglasses with prescription lenses, which we can prepare before you set off on your trek.