BackgroundTo assess the dimensions of Brucke's muscle, as the longitudinal portion, and of Muller's muscle and Iwanoff's muscle combined as circular and radial/reticular portions of the ciliary muscle.MethodsThe histomorphometric study included human globes that had been enucleated due to an ocular tumor or end-stage glaucoma. After immunohistochemical staining of the ciliary muscles, the histology slides were examined under a light microscope applying a digitized image analysis system.ResultsThe study included 55 globes [axial length 25.63.0mm (range 21.0mm-36.0mm)] from 55 patients [mean age, 33.7 +/- 18.3years (range:1-66years)]. Length of Brucke's muscle (mean 3.40 +/- 0.76mm) increased with longer axial length (P<0.001; regression coefficient beta: 0.52) and was not significantly associated with age (P=0.12), presence of glaucoma (P=0.11) or Brucke's muscle thickness at the scleral spur (P=0.32), at the site of the maximum thickness of the ciliary body (P=0.84) or at the posterior end of Muller's/Iwanoff's muscle (P=0.66), or with thickness (P=0.29) and cross-sectional area (P=0.85) of Muller's/Iwanoff's muscle. Mean distance between Brucke's muscle end and the ora serrata measured 1.73 +/- 1.13mm and increased with longer axial length (P<0.001; beta: 0.46). Distance from the scleral spur to the ora serrata (mean: 4.94 +/- 1.42mm; range: 3.08-9.09mm) increased with longer axial length (P<0.001; beta: 0.61). Maximal thickness (mean: 245 +/- 125m) and cross-section area (mean: 0.19 +/- 0.11mm(2)) of Muller's/Iwanoff's muscle decreased significantly with the diagnosis of glaucoma (P=0.02;beta:-0.38) and longer axial length (P=0.03; beta: -0.35).Conclusions p id=Par4 Length of Brucke's muscle increased with axial length of the globe, while its cross-sectional area was independent of axial length. Muller's/Iwanoff's muscle decreased in cross-sectional area with longer axis, and in particular with the presence of glaucoma, while the dimensions of Brucke's muscle were not related to glaucoma.