Patent ID: 8270089

Claim:
A method of thermoforming thermoplastic polyurethanes (TPU) into an ophthalmic lens having an optical surface wherein the resulting lens exhibits a reduction in the initiation and propagation of flaws, comprising the steps of: selecting a TPU having urethane repeating units (—NHCOO—) that are at least 23% by weight, wherein said TPU has an Elongation at Break value of between 140% and 160%, a flexural modulus above about 1,400 Mpa, an Abbe number between about 27 and about 45 and a refractive index, n d , between about 1.54 and about 1.60; thermoforming a highly transmissive, tintable ophthalmic lens from the TPU by one of injection molding and compression molding, wherein the formed lens contains about 99.5% TPU by weight and about 0.5% additives by weight, wherein the additives include an antioxidant, an ultra-violet light absorbers, and a hindered amine light absorber to stabilize progressive yellowing of the lens; tinting the thermoformed lens; coating the tinted lens with at least one protective layer; and drilling through the coating and the tinted lens to form a bore bordered by a sidewall, wherein the stated weight percentage of urethane repeating units (—NHCOO—) renders an optical surface and a sidewall with improved containment of flaws created in the coated, tinted TPU lens during drilling so that flaws are less likely to grow and propagate causing cracking and crazing in the tinted lens and protective coating layer.