HISTOCHEMICAL STAINING OF ORBICULARIS OCULI MUSCLE IN ECTROPION AND ENTROPION

A histochemical study of orbicularis oculi was undertaken to test the hypothesis that there is a difference in the percentage and size of mu scle fibre types which accounts for the development of involutional ec tropion or entropion. Wedge excisions from lower lids of patients unde rgoing repair of these conditions were frozen-sectioned and stained hi stochemically to reveal muscle fibre types. Five ectropion and five en tropion specimens were obtained, and the percentage of type 1 and type 2 fibres, fibre perimeters and fibre diameters were measured. An abun dance of type 2 fibres was found in both ectropion (mean 89.6%) and en tropion (mean 82.6%). No significant difference was found with respect to fibre type, perimeter or diameter when ectropion was compared with entropion or when either was compared with normals. Type 2 fibres wer e larger than type 1 in both ectropion and entropion. We conclude that no significant difference could be identified between orbicularis mus cle fibres in ectropion, entropion and normals to account for the deve lopment of the eyelid malpositions.