In contrast to the situation with children, who usually present with concomitant squint associated with hypermetropia, the sudden onset of a squint in adult life is extremely disabling because of intractable double vision. The double vision is less apparent when the lesion is more central, involving the level of the cranial nerve nucleus or above. In the latter case, the patient tends to complain more of blurred vision and confusion.
A carefully taken history can reveal the diagnosis. First, it is necessary to ensure that the double vision is only present with both eyes open and then the patient can be questioned about the position of the second image and whether the separation of the images is maximal in any particular direction of gaze. The duration and constant or intermittent nature of the squint must be determined, as must the history of any associated disease, past or present.
Once the history has been obtained, the nature of the squint can be investigated by the cover test and measured by the Maddox wing and Maddox rod. An accurate record of the impaired muscle action can be recorded on the Hess screen.
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