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Penetrating eye injuries are a common complication of severe motor vehicle accidents. The majority of cases accompany facial laceration when the head of a front seat occupant passes forward, and then back, through the broken windshield. The frequency of such injuries has been greatly reduced since legislation was introduced to make the wearing of seatbelts for all occupants and the use of laminated windshield glass compulsory. Glass entering the car through an open side window from a broken external rear view mirror is an uncommon but potentially preventable cause of severe ocular injury. First reported in 1990 by Keenan1 there have been two subsequent reports from Australia.2,3 We report two further cases and highlight deficiencies in legislation regarding the manufacture of external rear view mirrors.
A 17 year old man was driving a 1987 registered Fiat Uno when the driver’s external rear view mirror struck an oncoming van. The mirror broke and a fragment of glass passed through the open side window and hit his left eye. He sustained a corneal and scleral laceration but the lens and iris were not damaged. Following primary repair he made an uneventful postoperative recovery and retained a corrected visual acuity of 6/9 with spectacles.
A 22 year old woman passenger of a 2002 registered Peugeot 206 was struck in the right eye when the side mirror struck the mirror of a parked car. The mirror was broken and a fragment of glass entered her right eye through the open passenger window. She sustained a large corneal and scleral laceration with loss of the majority of the iris and damage to the lens. She underwent primary repair of the laceration with lens aspiration and anterior vitrectomy. She subsequently required a second vitrectomy with gas injection for vitreous gel incarceration and a retinal tear. She regained a visual acuity of 6/24 with a contact lens correction, but further improvement was prevented by corneal scar.
Broken rear view mirrors have previously been identified as a cause of severe ocular injuries.1–3 The two cases we describe occurred in similar circumstances and both patients sustained penetrating eye injuries caused by glass from the broken external rear view mirror entering the car through an open window. The external rear view mirrors project beyond the body of the car and in both cases the mirror was broken following a collision with another vehicle in which the wing mirrors were clipped. No other vehicle damage occurred.
All exterior rear view mirrors fitted to cars in the United Kingdom have to comply with the European Community Directive 71/127/EEC which was last amended in 1988 (Directive 88/321).4 This requires mirrors designed for use in cars to undergo a “pendulum test” using a 7 kg weight on a pendulum of 1 metre length released at a 60 degree angle from the vertical to represent the impact of a head hitting the mirror. The test is performed with the weight hitting both the reflecting surface side and repeated on the opposite surface. If, at the end of this test, the glass of the mirror breaks, any fragments should adhere to the back of the protective housing. However, the directive further specifies that:
Partial unsticking of the glass is permitted provided that this does not exceed 2.4 mm either side of the cracks. It is acceptable for small shards to detach themselves from the surface of the glass at the point of impact.
The reflecting surface shall be made of safety glass.
It is therefore permissible for small splinters of glass to become detached from the surface of the glass at the point of impact, which is the case for any automobile safety glass. However, in both our cases the fragments appear to have been released from the mirror by spalling following a relatively high velocity impact on the reverse of the mirror housing. The released glass fragments had sufficient momentum to pass through the open window of the car and penetrate the eye. The test described above simulates an object striking the mirror at a velocity of 3.1 ms−1, compared to a velocity of 13.4 ms−1 when the mirror of a car travelling at 30 miles per hour hits a stationary object. This velocity would be considerably higher if the car mirror clipped an oncoming car.
These cases highlight that there is a continuing risk of severe eye injury following an impact on the back surface of an external rear view mirror. Current legislation is based on a test that does not replicate the most probable circumstance of impact or the associated risk to the eye. The test is based on the effect of a low velocity impact, as opposed to the high velocity impact that would result from two cars passing in opposing directions. Replacing the glass with plastic would be an option to reduce the risk, although current plastic surfaces do not have the resistance to abrasion of glass which could result in scratches causing distracting light scatter. Avoiding driving with the side windows down, or repositioning the external mirrors are further options.
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