External auditory exostosis is attributed to hyperostosis of the temporal bone, and usually found bilaterally. The mechanism for development of exostosis is believed to be a resultant of exposure to cold water and cold air (particularly below 19ºC)1; however, the condition is considered to be idiopathic. Contrary to this widespread belief, we recently documented exostosis in surfers limited to warm water conditions, with water temperatures ranging from 20.6ºC (69.1°F) in winter to 28.2ºC (82.8°F) in summer.

Exostosis is typically diagnosed by otoscopic examination with severity reported as Grade 0 (no exostosis identifiable), Grade 1 (≤33percent obstruction), Grade 2 (≥34% to ≤66% obstruction) or Grade 3 (≥67% obstruction) (Figure 1). In Grade 1, exostosis is usually asymptomatic; however, increased severity is associated with symptoms which can include water trapping, recurrent cerumen blockage, otitis externa, otalgia and deterioration of hearing. The treatment currently available for Grade 3 or highly symptomatic exostosis, is surgical removal; however, there are risks associated with this procedure which can include permanent hearing loss, facial nerve injury, tympanic membrane perforation and infection.

Exostosis is the most common benign tumour of the external auditory canal in surfers (and other aquatic enthusiasts) with an estimated 60–74% reported to have at least Grade 1 in a number of studies and as high as 95–100% in professional surfers. In our recent study of exostosis prevalence among surfers,7 we encountered

difficulty with determining severity in a number of the participants (approximately 20%) where their degree of stenosis was not clearly identifiable as Grade 1, Grade 2 or Grade 3.

Although established clinical best practice for diagnosis of exostosis and its severity is based upon visual estimate of the degree of stenosis during the otoscopic exam, determination of the severity can be problematic when a clearly defined severity is not evident. The visual estimate is also problematical when attempting to determine progression of the disorder (i.e., serial otoscopy). We therefore sought a simple, efficient methodology whereby clinicians can accurately determine the severity of the condition (occlusion of external auditory canal) which is applicable for a patient visit or serial otoscopy over time.

In this study, we followed the AGREE reporting for clinical practice. Initially, we conducted a review of computer-aided design and drafting software programs that would provide analyses (diameter for calibration and perimeter for area determination) of irregularly shaped objects. Ideally, the software program would be designed for medical and/or biological analyses and with an established high validity and reliability.