Strabism, hemianopsia and the sundial of Mawas and Franceschetti

The artifact: The artifact is a light rectangular slate of black cardboard showing two white lines at 40 degrees angle. It provokes physiological dipl opia in lateral vision. Background: In normal subjects, the right oblique line stimulates the right nasal hemiretina, perceived as an oblique line, and the left temporal hemi retina, perceived as a vertical line, both lines being on the right: hand s ide. Likewise, the left oblique line is seen as two lines on the left hand side. The 4 lines form and M and a W combined. The strabismus subject sees 3 lines for he neutralizes one; the alternating squint sees only 2; the het erophoric sees 4 lines, two of which blurred, and the hemianopic sees only part of the dial. Results: The subject must select the image he sees from an array of possibi lities shown on the back of the dial. From 5 years of age on, normal subjec ts select the X or the "butterfly"; hemianopic subjects correctly describe the loss of either the left or right field. Conclusions: The sundial facilitates both the screening and the treatment o f binocular vision disorders. Bangerter's hemifilter will be used in associ ation with exercises for physiological diplopia at home under monthly ortho ptic control. All this made it: possible to obtain useful peripheral fusion in early onset strabismus.