Dimensions of the ciliary muscles of Brücke, Müller and Iwanoff and their associations with axial length and glaucoma.
BACKGROUND
To assess the dimensions of Brücke's muscle, as the longitudinal portion, and of Müller's muscle and Iwanoff's muscle combined as circular and radial/reticular portions of the ciliary muscle.


METHODS
The 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.


RESULTS
The study included 55 globes [axial length 25.6 ± 3.0 mm (range 21.0 mm-36.0 mm)] from 55 patients [mean age, 33.7 ± 18.3 years (range:1-66 years)]. Length of Brücke's muscle (mean 3.40 ± 0.76 mm) 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 Brücke'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 Müller's/Iwanoff's muscle (P = 0.66), or with thickness (P = 0.29) and cross-sectional area (P = 0.85) of Müller's/Iwanoff's muscle. Mean distance between Brücke's muscle end and the ora serrata measured 1.73 ± 1.13 mm and increased with longer axial length (P < 0.001; beta: 0.46). Distance from the scleral spur to the ora serrata (mean: 4.94 ± 1.42 mm; range: 3.08-9.09 mm) increased with longer axial length (P < 0.001; beta: 0.61). Maximal thickness (mean: 245 ± 125 μm) and cross-section area (mean: 0.19 ± 0.11 mm2) of Müller'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
Length of Brücke's muscle increased with axial length of the globe, while its cross-sectional area was independent of axial length. Müller's/Iwanoff's muscle decreased in cross-sectional area with longer axis, and in particular with the presence of glaucoma, while the dimensions of Brücke's muscle were not related to glaucoma.
['Mao|Ying|Y|', 'Bai|Hai Xia|HX|', 'Li|Bin|B|', 'Xu|Xiao Lin|XL|', 'Gao|Fei|F|', 'Zhang|Zhi Bao|ZB|', 'Jonas|Jost B|JB|http://orcid.org/0000-0003-2972-5227']
D000199:Actins D000293:Adolescent D000328:Adult D000368:Aged D058452:Axial Length, Eye D002648:Child D002675:Child, Preschool D002924:Ciliary Body D015353:Eye Enucleation D005260:Female D005901:Glaucoma D006801:Humans D007150:Immunohistochemistry D007223:Infant D008297:Male D008875:Middle Aged D009130:Muscle, Smooth
Ciliary muscle Glaucoma Scleral spur Bruch’s membrane Brücke’s muscle Intraocular pressure Iwanoff’s muscle Müller’s muscle