Experimental increase in accommodative potential after neodymium : yttrium-aluminum-garnet laser photodisruption of paired cadaver lenses

Purpose. Loss of lens elasticity is one of several proposed mechanisms resp onsible 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 accommodat ive potential as measured by polar strain. Design: Experimental human autopsy eye study. Participants and Controls. Thirty-six cadaver lenses were tested to determi ne the age-dependent polar strain. Eleven lens pairs. were then tested. wit h one lens treated with neodymium:yttrium-aluminum-garnet (Nd:YAG) laser an d the other left untreated before rotation as an age control. I Testing: Using a custom-made rotational apparatus (described by Fisher, 197 1), freshly excised cadaver lenses (<48 hours postmortem) were rotated at 1 ,000 rpm on a 9-mm diameter pedestal to simulate the physiologic pull of th e zonules. Lenses were initially tested to determine the age-dependent pola r 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 suprathres hold pulse placed in a central annular pattern of 2- to 4-mm diameter. Trea tment energies varied from 2.5 to 7.0 mJ/pulse, depending on the relative c larity of the lenses. Polar strain was both microscopically measured and ca lculated from projected photographs before and after rotation of both lased and unlased lenses. Statistically significant differences were determined by paired. t test. Main Outcome Measures: Polar strain (decrease in axial thickness with rotat ion) of the lens. Results. An age-dependent decrease in polar strain was observed that parall eled the findings of Fisher. Both measured and projected polar strain were greater in the lased than unlased lens, and this difference was highly sign ificant by paired t test (P = 0.001 and P = 0.004, respectively). Conclusions: Age-dependent loss of lens elasticity, (polar strain) can be e xperimentally reversed (increased) by selective intralenticular photodisrup tion. Ophthalmology 2001;108:2122-2129 (C) 2001 by the American Academy of Ophthalmology.