Materials glossary / Standard and mark
Reader strength (diopter)
On the label: Diopter · Standard and mark
What it is
The power of a reading lens in diopters, +1.00 to +4.00 in steps of 0.25; higher means closer focus. Off-the-shelf readers use the same strength in both eyes.
Standard and marks: The marks, tests and laws behind the words on a label: karat stamps, UV400, ANSI Z80.3, the FTC Jewelry Guides, Prop 65.
Wikidata: Unit of optical power. Q193933 →
In the research
1,432 PubMed papers mention it with jewelry, allergy, eyewear or UV; the three most recent:
- Pupil Size Associations and Refractive Error Tolerance in Enhanced Monofocal Intraocular Lenses With Different Central Optic Designs · Journal of refractive surgery (Thorofare, N.J. : 1995), 2026
- Sushrutha's Reflex: A Novel Clinical Sign for Detecting Focal Macular Surface Elevation · Journal of vitreoretinal diseases, 2026
- Development of a smartphone-based retinal imaging device for stable fundus imaging · Japanese journal of ophthalmology, 2026
A paper is a paper, not a verdict: titles are listed so you can read them, and a study on one fabric or one filter says little about the piece in your hand.
Other standard and marks
Clasp & Lens describes materials from the public record and does not appraise, grade or test pieces; what a listing states is the supplier's statement. If a piece causes a rash, take it off; a reaction that spreads or blisters is a doctor's question, and sunglasses are no substitute for impact-rated eye protection where that is required.