It is currently unknown how much exophthalmos may be noticeable to an observer. The authors determined the threshold for detection of exophthalmos may be 4 millimeters.
Purpose: To determine the threshold for detection of exophthalmos by an observer.
Methods: The Massachusetts Eye and Ear Infirmary Ophthalmic Plastics imaging database was used to select 28 photographs of patients with unilateral exophthalmos measuring between 1 to 11 mm for the study group and 28 photographs of patients without exophthalmos for the control group. One hundred ophthalmology attendings, residents, medical students, and technicians reviewed each photograph. Participants commented on whether the patient appeared "normal" or "abnormal."
Results: Eighty-one percent of the control patients were correctly identified as "normal." In comparison, 60% of patients with 1 mm of exophthalmos (p < 0.001), 53% of patients with 2 mm of exophthalmos (p < 0.001), 46% of patients with 3 mm of exophthalmos (p < 0.001), 35% of patients with 4 mm of exophthalmos (p < 0.001), and 40% of patients with 5 mm of exophthalmos (p < 0.001) were identified as "normal." The vast majority of patients (91.9%, p < 0.001) with 6 mm of exophthalmos were identified as "abnormal," and almost all patients (97.9%, p < 0.001) with more than 6 mm of exophthalmos were also described as having an "abnormal" appearance.
Conclusions: Greater than half of the patients with 1-2 mm of exophthalmos appear as "normal" as the control patients. In comparison, the majority of patients with 4-5 mm of exophthalmos and nearly all the patients with 6 mm of exophthalmos and greater appear "abnormal." Our data suggests that the point at which exophthalmos becomes clinically perceptible to the majority of observers is 4 mm. There may be patients with 3 mm of exophthalmos and greater with orbital pathology being "missed" on cursory external examinations by general ophthalmologists, optometrists, and general practitioners.