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PURPOSE.To investigate the elastic properties of human lens zonules as a function of age in presbyopes.METHODS. We studied 16 presbyopic human donor eyes (ages 47-97). Anterior eye sections with crystalline lens, zonules, ciliary body, and sclera were stretched radially. The stretching device consisted of a chamber filled with balanced salt solution and eight radial hooks to hold the anterior eye section. Radial stretching was created with a stepper motor connected to a digital outside micrometer for linear displacement and digital balance for force measurement. Three eye globes were used to test our methodology. For 13 eye globes, the spring constant, elastic modulus of the zonular system, and Young's modulus of the zonules were calculated. RESULTS.We found linear dependence for force-elongation and force-strain relationships at all ages. In young presbyopic eyes (ages 47-60), the Young's modulus of the zonules was 340 mN/ mm 2 , whereas in older eyes (ages 83-97) it was significantly lower at 270 mN/mm 2 . However, the correlation coefficient between Young's modulus and age (47-97 years) was not significant with P ¼ 0.063. CONCLUSIONS.The zonular system in presbyopic eyes was linear elastic, and the Young's modulus of the zonules decreased 20% from presbyopic age to late presbyopic age. However, there was no significant correlation between Young's modulus and age in presbyopes. (Invest Ophthalmol Vis Sci. 2012;53:6109-6114)

When stretching tests are conducted on the anterior segment, significant circumferential tensions develop in the ciliary body. This means that the forces applied to the lens and zonules cannot be related directly to the forces applied by the external loading system. If radial cuts are introduced in the ciliary body prior to testing, however, then this difficulty does not arise.

Purpose: To evaluate a new nuclear cataract grading system which is intended as a surgical guidance system to predict lens hardness before cataract surgery. Methods: The new BCN 10 grading system consists of frontal and cross-sectional slit-lamp images of human eye lenses, ranging from a completely transparent lens nucleus to a totally black nuclear cataract. Validation was done with 9 observers for 110 cases. Two modalities were applied, and observers were asked to use only whole digits and then half digits for grading. Results: Repeatability with regard to test-retest differences showed a mean limit of agreement of 1.70 for whole digits and 1.32 for half digits. The absolute test-retest difference was close to zero for low as well high degrees of cataracts. Reliability for the entire group of 9 observers yielded an intraclass correlation coefficient which was within the same confidence interval, i.e., 0.991-0.995, for whole digits and half digits. Conclusions: BCN 10 grading repeatability was not affected by the severity of the cataract. It showed very good repeatability. Repeatability was significantly higher when the observers used half digits compared to whole digits. Reliability was found to be very good as well, independently of the use of whole or half digits.

Wedge resection is a safe and moderately effective procedure in the correction of high astigmatism after penetrating keratoplasty for keratoconus. Histopathologic changes confirm a true late progression of the disease in the host cornea. Keratoconus may be a disease that affects the entire cornea, and surgical resection does not cure the disease.

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