Abstract
Purpose: :
To measure ex-vivo the stress-strain relationship of the human lens zonules.
Methods: :
Eleven presbyopic human donors eyes were classified by age in three groups (median age 60, 73 and 90 years) and measured in a device consisting of a rigid bench for holding and stretching coronal eye sections including the ciliary-lens zone. Radial stretching was created by a stepper motor coupled to a digital outside micrometer for linear displacement and distance measurement, and a digital balance for load measuring.
Results: :
Zonular elongation by 200 µm produced a mean load of 4.4; 3.3 and 2.8 mN in the different age groups (60, 73 and 90 years respectively). Increased elongation above physiological limits to 650 µm resulted in a mean load of 9.2; 6.9 and 6.2 mN, respectively. (10 mN = 1.02 g)
Conclusions: :
The force needed to stretch the human lens zonules decreases between the age of 60 to 90 years by about 30%.
Keywords: accommodation • aging • presbyopia