In vitro dimensions and curvatures of human lenses

Abstract

The purpose of this study was to determine dimensions and curvatures of excised human lenses using the technique of shadowphotogrammetry. A modified optical comparator and digital camera were used to photograph magnified sagittal and coronal lens profiles. Equatorial diameter, anterior and posterior sagittal thickness, anterior and posterior curvatures, and shape factors were obtained from these images. The data were used to calculate lens volumes, which were compared with the lens weights. Measurements were made on 37 human lenses ranging in age from 20 to 99 years. These showed that lens dimensions and the anterior radius of curvature increase linearly throughout adult life while posterior curvature remains constant. The relative shape (or aspect ratio) of the posterior lens is unchanged through adult life since both equatorial diameter and posterior thickness increase at the same rate. The ratio of anterior thickness to posterior thickness is constant at 0.70. It is suggested that in vivo forces alter the apparent location of the lens equator, that the in vitro lens shape corresponds to the maximally accommodated shape in vivo and that the shapes of the accommodated and unaccommodated lens progressively converge toward each other due to lens growth with age, with a convergence point located near the age of total loss of accommodation (55-60 years). Together, these observations provide additional support for the Helmholtz theory of accommodation.

Accommodation of the human lens capsule using a finite element model based on nonlinear regionally anisotropic biomembranes

“…The radius of curvature was 6.98mm for the anterior and 5.62mm for the posterior lens capsule. These were consistent with measurements of an accommodated lens (Rosen et al 2006;Hermans et al 2007Hermans et al , 2009Kasthurirangan et al 2011;Lanchares et al 2012). The geometry obtained using a pressure of 5-6mmHg had slightly greater thickness, but the dimensions were still within the range of measurements and human models (Augusteyn et al 2011).…”

Quantification of Age-Related and per Diopter Accommodative Changes of the Lens and Ciliary Muscle in the Emmetropic Human Eye

“…Removal of the young lens from the eye will cause it to assume its most accommodated shape and decrease the equatorial diameter; thus, early in vitro studies that reported an increase in diameter with age were not necessarily showing an age-related increase. [48][49][50] An in vivo study of rhesus monkeys showed no change in LED with age, but the few in vivo human studies were equivocal. 15,41,47,51 The original MRI studies by Strenk and coworkers reported no change, while a more recent study comparing 18-to 29-year-old subjects to 60-to 70-year-old subjects found a slight increase of approximately 0.01 mm/ y.…”

Volume change of the ocular lens during accommodation

“…Most parameters needed for the sketches of the lenses were obtained or calculated from information available in the literature (4,5,12,25,28). Stepwise description of the construction from the available data is shown below.…”

“…Rosen et al (25), in their research on excised human lenses from cadavers (ages 20 to 99 yr), developed a linear regression analysis of curvatures of the anterior and posterior surfaces, as well as A-P sagittal thickness and equator diameter. Most of the formulas for creating the accommodated lenses were extracted from this study.…”