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ABSTRACT
A group of patients with the monofixation syndrome were assessed prospectively to compare performance on Titmus and Randot stereograms under monocular and binocular conditions. These patients achieved monofixation either as a result of surgery for infantile esotropia, or because of a partially accommodative esotropia or significant anisometropia. Their ability to detect elevation of the Titmus circles was not significantly better with two eyes as compared to that level achieved using only their monofixating eye. However, performance on the Titmus animals and on Randot circles or animals showed better discrimination. These data would suggest that the monocular clues available in determining elevation of the Titmus circles would invalidate establishing a diagnosis of monofixation.
The monofixation syndrome as popularized by Marshall Parks1 is generally viewed as a favorable outcome for children with many types of strabismus or anisometropia. The presence of peripheral fusion is felt to offer long-term stability to alignment and carries with it a good prognosis. It is assumed that stereoacuity in monofixators arises from the peripheral widening of Pannum's fusional space.
Monofixation generally has the following characteristics:
* A horizontal deviation less than 10 prism diopters,
* A macular scotoma in the nonfixating eye under binocular conditions,
* Peripheral NRC with fusional amplitudes,
* A phoria-tropia combination where cross cover measurement exceeds single cover measurement,
* Fusion of Worth-4-Dots at near but not at distance, and
* Stereoacuity between 67 and 3000 seconds of arc.
The stereo values of 3000 to 67 seconds of arc are derived from the Wirt stereotest which (copyright 1947, S. Edgar Wirt, PhD) actually goes down to 14 seconds of arc. When production of the Wirt stereotest was discontinued it weis replaced by the Titmus stereotest which has values from 3000 seconds of arc to 40 seconds of arc. The anomalous figure of 67 seconds of arc on the Wirt stereotest would then correspond to some intermediate between Titmus circle number six and number seven (80 and 60 seconds of arc stereoacuity respectively). Many types of stereotests are available but the Titmus stereotest is currently the most popular means available for assessing stereoacuity in an office practice.
MATERIALS AND METHODS
Twenty-two patients were assessed in a prospective fashion. Their ages ranged from 6 to 16 years...