ARCCA has investigated product liability cases where design decisions had unexpected consequences. In this case, a woman’s eye was lacerated when the frame of her eyeglasses unexpectedly fractured during a minor bump. ARCCA engineering and biomechanics experts worked together to analyze the design of the eyeglasses and the incident.

Steps Taken

ARCCA’s engineering experts conducted an investigation of the eyeglasses:

  • Examination of the fractured glasses frame indicated that the glasses were fractured by contact to the frame temples.
  • Microscopy of the fractured glasses showed that cracks had grown from where the temple of the glasses had holes cut to accommodate a decorative logo.
  • The glasses fractured in a way that created sharp-edged pieces near the wearer’s eyes.
  • Testing of exemplar glasses showed that this particular design was prone to fracturing where the decorative logo was placed.
  • Similar glasses, but without the logo, did not fracture at the temple or produce hazardous sharp edges.

exemplar showing holes that cause fracture

ARCCA’s biomechanics experts analyzed the accident:

  • The plaintiff’s account of the accident was compared with her documented injuries.
  • Alternative accident scenarios proposed by opposing experts were analyzed for consistency with the plaintiff’s medical records.
  • The direction of force identified by ARCCA’s engineering expert was compared with how the plaintiff’s body would have moved during the accident.

Final Findings

ARCCA engineering experts concluded that by designing the temples of the glasses to have a hole for the logo, the manufacturer had made the frame significantly weaker. The use of a brittle polymer caused the temple to fail in a way that produced sharp edges near the wearer’s eyes. The ARCCA engineering team tested similar alternative designs to demonstrate that using a different material and not cutting holes in the temples could have prevented the accident.


broken eye glasses hinge


ARCCA biomechanics experts found that the alternative accident scenarios proposed by the defense’s experts would have resulted in additional injuries that were not reported in the plaintiff’s medical history – such as orbital bone fractures. The plaintiff’s description of the accident was consistent with her injuries and with the failure mode identified by ARCCA’s engineering experts.



ARCCA engineering experts found that the glasses were defectively designed because they used a brittle material and placed holes in the temples that made them likely to fracture, creating sharp edges near the wearer’s eyes. ARCCA biomechanics experts found that the subject glasses failed during normal use.

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