Optomechanical response of human and monkey lenses in a lens stretcher.
OBJECTIVE
To quantify the forces necessary to change the shape and optical power of human and monkey lenses.


METHODS
Cynomolgus monkey (n = 48; age: 3.8-11 years), rhesus monkey (n = 35; age: 0.7-17 years) and human (n = 20, age 8-70 years) eyes obtained postmortem, including the lens, capsule, zonules, ciliary body, and sclera were mounted in an optomechanical lens-stretching system. Starting at zero load, the lenses were symmetrically stretched in a stepwise fashion in 0.25- or 0.5-mm steps. The load, lens diameter, inner ciliary body diameter, and lens power were measured at each step and the diameter- and power-load responses were quantified.


RESULTS
The diameter- and power-load responses were found to be linear in the physiologically relevant range of stretching. The average change in cynomolgus, rhesus, and human lens diameter, respectively, was 0.094, 0.109, and 0.069 mm/g in young lenses, and 0.069, 0.067, and 0.036, mm/g in older lenses. For the same lenses, the average change in lens power was -3.73, -2.83, and -1.22 D/g in young lenses and -2.46, -2.16, and -0.49 D/g in older lenses.


CONCLUSIONS
The force necessary to change the lens diameter and lens power increases with age in human and monkey lenses. The results agree with the Helmholtz theory of accommodation and with presbyopia theories that predict that the force required to disaccommodate the lens increases with age.
Manns
Fabrice
F
Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida 33136, USA. fmanns@miami.edu
Parel
Jean-Marie
JM
Denham
David
D
Billotte
Christian
C
Ziebarth
Noel
N
Borja
David
D
Fernandez
Viviana
V
Aly
Mohammed
M
Arrieta
Esdras
E
Ho
Arthur
A
Holden
Brien
B
D000065:Accommodation, Ocular / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology; D000818:Animals; D002648:Child; D002924:Ciliary Body / Q000033:anatomy & histology / Q000502:physiology; D006801:Humans; D007908:Lens, Crystalline / Q000033:anatomy & histology / Q000502:physiology*; D008252:Macaca fascicularis; D008253:Macaca mulatta; D008875:Middle Aged; D012029:Refraction, Ocular / Q000502:physiology*; D013314:Stress, Mechanical; D014019:Tissue Donors