Orbital protrusion index in Treacher-Collins syndrome: a tool for determining the degree of soft-tissue damage.

The relationship of measurements of the intercanthal width (en-en), the biocular width (ex-ex) and both eye fissures (ex-en), constituting the orbital protrusion index ex-ex x 100 (en-en) + (en-ex, r) + (en-ex, l) was used to analyze preoperative morphological developments in the orbits of 23 patients with Treacher Collins syndrome. The index permitted distinction between mildly and severely defective orbits, based on the degree of defective measurements and variations in relative sagittal positions. Optimal index values (mean, 94.0) were seen in 11 subjects with a slightly different sagittal level between the inner and outer commissures of the eye fissures, which created slightly protruding but still normal soft-tissue relief. The eye fissures in seven patients were moderately reduced in length. Orbits with higher indices (mean 98.1) (12 subjects) showed less differences in level between the two commissures of the eye fissures, producing a flattening in the surface relief. Eye fissure length was markedly subnormal in all patients.