title: Magnetic resonance imaging of aging, accommodating, phakic, and pseudophakic ciliary muscle diameters.
abstract: OBJECTIVE
  To quantify in vivo accommodative changes in the aging human ciliary muscle diameter in phakic and pseudophakic eyes.
  
  
  METHODS
  Department of Surgery/Bioengineering, UMDNJ-Robert Wood Johnson Medical School, Piscataway, and the Institute of Ophthalmology and Visual Science UMDNJ-New Jersey Medical School, Newark, New Jersey, USA.
  
  
  METHODS
  Images were acquired from 48 eyes of 40 people between the ages of 22 and 91 years, 1 eye of 32 phakic volunteers and both eyes of 8 patients who had monocular implantation of a single-piece AcrySof intraocular lens (IOL) (Alcon Laboratories). Images were acquired during physiological accommodation and with accommodation at rest, and the diameter of the ciliary muscle ring was measured.
  
  
  RESULTS
  Results show the ciliary muscle remains active throughout life. The accommodative change in its diameter (mean 0.64 mm) (P<.00001) was undiminished by age or IOL implantation. Preliminary data showed that the accommodative decrease in muscle diameter in phakic and pseudophakic eyes was statistically identical. The phakic eyes had a marked decrease in ciliary muscle diameter with advancing age for both accommodative states (P<.000001 and P<.000001), which did not appear to be altered by IOL implantation. The lens equator was constant with age in the unaccommodated human eye, resulting in decreased circumlental space with advancing age in the phakic eyes.
  
  
  CONCLUSIONS
  Although the undiminished ability of the ciliary muscle to decrease its diameter with accommodation can be relied on in strategies for presbyopia correction, even in advanced presbyopia, the decreasing circumlental space and its potential effects on zonular tension must also be considered.
authors.affiliation: Department of Surgery/Bioengineering, University of Medicine and Dentistry of New Jersey (UMDNJ)-Robert Wood Johnson Medical School, Piscataway, New Jersey, USA. sstrenk@wowway.com
authors.forename: Susan A
authors.initials: SA
authors.lastname: Strenk
authors.forename: Lawrence M
authors.initials: LM
authors.lastname: Strenk
authors.forename: Suqin
authors.initials: S
authors.lastname: Guo
mesh_terms: D000065:Accommodation, Ocular / Q000502:physiology*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D002924:Ciliary Body / Q000378:metabolism; D005260:Female; D006801:Humans; D019654:Lens Implantation, Intraocular; D007908:Lens, Crystalline / Q000502:physiology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology; D009130:Muscle, Smooth / Q000378:metabolism*; D018918:Phacoemulsification; D019591:Pseudophakia / Q000378:metabolism*