Familial intermittent diplopia: a report of two cases

The presence of sufficient muscle balance and bifovial fixation to prevent a break in fusion resulting in diplopia, even under conditions of hypoxia, fatigue, stress, and peripheral gaze, has been of concern in aviation medicine since 1917. Considerable resources are still expended obtaining, reporting, and storing test results, using procedures that undoubtedly exceed the skills of many examiners, when denials are rare, few inflight breaks in fusion have ever been reported, and most known cases of diplopia are from the history. We have recently examined a 54-yr-old employee with a 5-yr history of several daily episodes of incapacitating diplopia, and we have information about his 48-yr-old brother who has a similar history. When asymptomatic, both have normal vision test results. Detection was from the histories; the diagnosis remains uncertain. The ease of concealment, rare test value, and prevalent examiner skills are of concern. The importance of the history is reaffirmed.