To the Editor:We read with interest the case report "Elderly Man with an Orbital Blowout Fracture After a Motor Vehicle Accident"by Dr K. Nguyen (July 2005). Two points need correction. The author quotes a mean value of 78 mJ as the force required to cause an orbital blowout fracture. However, the millijoule is a unit of energy, not a unit of force, which is measured in newtons. The authors of the original study reported this value as the mean energy required to fracture the orbital floor of human cadavers.¹ In addition, the author suggests that the Figure shows subcutaneous emphysema resulting from the inferior orbital wall fracture, but this abnormality seems localized in the left periorbital soft tissues lateral to the nose rather than posterior to the nose in the midline as indicated by the arrow. Otherwise, we greatly enjoyed the article and found the content very useful.

James Bradley Summers, MD
Department of Radiology
University of South Alabama, Mobile
Joseph Kaminski, MD
Department of Radiology
Medical College of Georgia, Augusta

1. Bullock JD, Warwar RE, Ballal DR, et al. Mechanisms of orbital floor fractures: a clinical, experimental, and theoretical study. Trans Am Ophthalmol Soc. 1999;97:87-110.