title: The stress on the anterior lens surface during human in vivo accommodation.
abstract: OBJECTIVE
  To determine the qualitative change in stress on the lens capsule during in vivo human accommodation.
  
  
  METHODS
  Nine subjects (mean age: 30 years; range: 25-38 years) were studied, each of whom had undergone a phakic refractive intraocular lens (PRL) surgical procedure. The change, during accommodation, of stress on the surface of the anterior lens capsule (ALS) was determined by employing high-resolution anterior segment optical coherence tomography (OCT). This was done by comparing the ratio of the intensity of the image from the anterior surface of the natural lens (ALS) to the images of the anterior corneal surface (ACS), posterior corneal surface (PCS) and the posterior surface of the phakic refractive intraocular lens (PPRLS) before and during accommodation.
  
  
  RESULTS
  The intensities of the OCT images of the ACS and PPRLS did not significantly change during accommodation when compared with their respective baselines, while the intensity ratios: ALS/ACS, ALS/PCS and ALS/PPRLS all significantly increased during accommodation (p<0.01).
  
  
  CONCLUSIONS
  The stress on the anterior lens capsule is increased during in vivo human accommodation. This observation is consistent with a mechanism of accommodation in which zonular tension increases with accommodation, which is opposite to the predictions of the Helmholtz theory.
authors.affiliation: Department of Physics, University of Texas at Arlington, Arlington, TX, USA. ron@2ras.com
authors.forename: R A
authors.initials: RA
authors.lastname: Schachar
authors.forename: A
authors.initials: A
authors.lastname: Koivula
mesh_terms: D000065:Accommodation, Ocular / Q000502:physiology*; D000328:Adult; D005260:Female; D006801:Humans; D007903:Lens Capsule, Crystalline / Q000502:physiology*; D008297:Male; D013314:Stress, Mechanical; D041623:Tomography, Optical Coherence / Q000379:methods