Inside Constar’s six-factory contact lens production line

Constar says its Gansu and Hunan plants make more than 15 million contact lenses a month through a 55-day process that starts with liquid monomer and ends with sterilized vials. The company’s manufacturing line spans cast molding, hydration, pigmentation, inspection, packaging and terminal sterilization for customers in more than 40 countries.

Why it matters: - Contact lenses are medical devices, so manufacturing quality directly affects eye safety, comfort and vision. - Constar’s scale shows how mass-market lenses move from chemistry to a sterile consumer product through tightly controlled industrial steps. - The company’s production model matters for global brands and distributors that rely on consistent supply across more than 40 countries.

What happened: - Constar outlined how its contact lenses are made, from liquid monomer to sterilized vial, across six production facilities. - The company said the line uses more than 500 automated machines and more than 70 inspection units. - Constar says the plants produce more than 15 million lenses each month. - The process covers injection molding, polymerization, hydration, pigmentation, quality inspection, packaging and sterilization.

The details: - The production process begins in a controlled mixing room where hydroxyethyl methacrylate, silicone hydrogel blends or tinted formulations are prepared. - Raw-material ratios determine water content, oxygen permeability, refractive index and mechanical strength. - Constar says the formulation lab operates within an ISO 13485 quality management system. - Each raw-monomer batch is tested for purity, viscosity and polymerization readiness before entering the line. - Cast molding shapes the lens in precision CNC-machined molds made from optically clear cycloolefin or polypropylene. - A measured drop of liquid monomer, typically 50–80 microliters, is dispensed into the mold. - UV light at 365 nm or thermal energy polymerizes the monomer into a solid hydrogel network in 60–120 seconds. - The molded lens is removed dry and rigid before hydration. - Hydration submerges the lens in phosphate-buffered saline at 25–35°C for 2–24 hours, depending on material. - The process brings lenses to their target diameter of 14.0–14.5 mm and water content of 38% for hydrogel or 43%–55% for silicone hydrogel. - Constar says real-time sensors monitor swelling rate and final dimensions during hydration. - Colored lenses use a sandwich-printing process with FDA-approved pigments sealed between two transparent hydrogel layers. - Constar says the pigment never contacts the eye directly because the color layer is fully encapsulated. - The company says its laser engraving system, introduced in 2020, produces higher-resolution patterns than conventional printing. - Constar says its pigment library includes more than 300 color patterns for natural and fantasy looks. - Quality inspection includes automated optical inspection, Dk/t testing, power verification, water-content analysis and packaging checks. - AOI systems measure diameter, base curve, center thickness, edge profile and surface defects. - Constar says its silicone hydrogel formulation achieves Dk/t values above 110. - The company says lens power is measured across a prescription range from -10.00 to +6.00 D. - Packaging places each approved lens into a thermoformed polypropylene blister vial with 0.5–1.0 mL of sterile saline. - The vial is heat-sealed with an aluminum foil laminate lid and then inserted into a printed carton with a destination-market leaflet. - Constar says it supports OEM and ODM packaging, including custom cartons, multi-language inserts and regulatory labeling. - Terminal sterilization uses moist heat autoclave processing at 121°C for 30 minutes, according to the company’s process description. - The release says some manufacturers also use gamma irradiation or ethylene oxide for heat-sensitive materials. - Constar says it validates sterilization cycles to ISO 11135 and ISO 11137 and uses biological indicators to confirm efficacy. - The company says the full bulk-production timeline is about 55 days, while sample lead times are 3–7 days. - Constar says the day-by-day flow runs from raw-material testing and molding to hydration, pigmentation, inspection, packaging, sterilization, release and shipping.

Between the lines: - The manufacturing process is built around redundancy and automation because contact lens defects can have direct medical consequences. - Constar’s emphasis on closed-loop control, robotic handling and real-time inspection signals a push for lower defect rates and more consistent optical performance. - The company’s focus on colored lenses shows that cosmetic products still have to meet the same sterility and material-safety requirements as clear lenses.

What’s next: - Constar says lenses continue through documentation and shipping after sterility testing. - The company’s output is positioned for branded and OEM/ODM customers that need regulatory-ready products for different markets. - The release suggests future production will keep centering on automation, laser-patterned coloring and tighter inspection controls.

The bottom line: - A contact lens may look simple in the package, but Constar’s process shows it is the product of chemistry, precision molding, hydration, inspection and sterilization before it ever reaches an eye.