Frame materials explained: acetate, metal, titanium, TR90What each material is, how it is made and what it costsLens materials and refractive indexCR-39, polycarbonate, Trivex, 1.56, 1.60, 1.67, 1.74Single vision, bifocal and progressive lensesHow multifocal lenses are designed and soldLens coatings and treatmentsHard coat, anti-reflective, hydrophobic, UV, blue-light, mirrorSunglass lens standards and categoriesUV400, filter categories 0–4, polarisation, EN ISO 12312-1, ANSI Z80.3, AS/NZS 1067Safety eyewear standardsEN 166, ANSI Z87.1, AS/NZS 1337, CSA Z94.3 and markingsFrame sizing, standards and measurementsISO 12870, eye size, bridge, temple, the boxing systemHow prescription lenses are madeBlanks, surfacing, free-form generators, coating, edging, quality checksContact lenses: materials, modalities and regulationHydrogel, silicone hydrogel, RGP; daily, monthly; FDA, CE MDR, PMDABuying eyewear from a factory: OEM, ODM, MOQ and samplingHow the frame trade works between brand and factoryImport duties, HS codes and regulationsHS 9001, 9003, 9004; CE, FDA, BIS, and what customs will askWhy good spectacles are cheap in Japan and KoreaOne-price chains, same-day lenses and Seoul's optical marketsReading glasses and the ready-reader tradePowers, quality checks, markets, and where they are made