title: Experimental increase in accommodative potential after neodymium: yttrium-aluminum-garnet laser photodisruption of paired cadaver lenses.
abstract: OBJECTIVE
  Loss of lens elasticity is one of several proposed mechanisms responsible for the decline in accommodation with age and is the most accepted explanation for presbyopia. We wish to confirm the lens elasticity premise and attempt to experimentally reverse the age-dependent loss of accommodative potential as measured by polar strain.
  
  
  METHODS
  Experimental human autopsy eye study.
  
  
  METHODS
  Thirty-six cadaver lenses were tested to determine the age-dependent polar strain. Eleven lens pairs were then tested with one lens treated with neodymium:yttrium-aluminum-garnet (Nd:YAG) laser and the other left untreated before rotation as an age control.
  
  
  METHODS
  Using a custom-made rotational apparatus (described by Fisher, 1971), freshly excised cadaver lenses (<48 hours postmortem) were rotated at 1000 rpm on a 9-mm diameter pedestal to simulate the physiologic pull of the zonules. Lenses were initially tested to determine the age-dependent polar strain. One lens in a pair was then treated with an Nd:YAG laser and the other left untreated before testing. Treatment consisted of 100 suprathreshold pulse placed in a central annular pattern of 2- to 4-mm diameter. Treatment energies varied from 2.5 to 7.0 mJ/pulse, depending on the relative clarity of the lenses. Polar strain was both microscopically measured and calculated from projected photographs before and after rotation of both lased and unlased lenses. Statistically significant differences were determined by paired t test.
  
  
  METHODS
  Polar strain (decrease in axial thickness with rotation) of the lens.
  
  
  RESULTS
  An age-dependent decrease in polar strain was observed that paralleled the findings of Fisher. Both measured and projected polar strain were greater in the lased than unlased lens, and this difference was highly significant by paired t test (P = 0.001 and P = 0.004, respectively).
  
  
  CONCLUSIONS
  Age-dependent loss of lens elasticity (polar strain) can be experimentally reversed (increased) by selective intralenticular photodisruption.
authors.affiliation: Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
authors.forename: R R
authors.initials: RR
authors.lastname: Krueger
authors.forename: X K
authors.initials: XK
authors.lastname: Sun
authors.forename: J
authors.initials: J
authors.lastname: Stroh
authors.forename: R
authors.initials: R
authors.lastname: Myers
mesh_terms: D000065:Accommodation, Ocular / Q000502:physiology*; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology; D004547:Elastic Tissue; D006801:Humans; D053685:Laser Therapy; D007908:Lens, Crystalline / Q000502:physiology* / Q000601:surgery*; D008875:Middle Aged; D011305:Presbyopia / Q000503:physiopathology