Elastic Characteristics of Human and Primates Lens Capsules Assessed ex vivo

Abstract

 

Abstract:

 

To determine in situ the elastic properties of the lens capsule pre–post lens content removal.

 

4 human, 4 rhesus and 5 cynomolgus fresh eyes underwent 4 mm lens stretching on EVAS (Parel et al, ARVO2002) before and after lens content removal via a 1mm peripheral capsulorhexis (Graefes Arch Clin Exp Ophth 1986;224:165–73). Accommodation amplitude (AA), natural (Øn) and empty (Øe) lens capsule diameters in the equatorial plane were recorded as a function of stretch force (g). The empty capsule surface area (Se) was calculated and compared to the average age–matched intact lens capsule surface (Sn) calculated from shadowphotogrammetric measurements of a large series of crystalline lenses (Rosen AM et al, ARVO 2002) and the surface shrinkage (SS) calculated.

 

Stretching force varied 5–9g but there was no statistical relationship with species or age. For whole lenses, stretched lens diameter (Øn st) changed less than 2.4% in old human and >5% in young primates. After emptying the capsular bag, the capsule diameter (Øe st) expanded by 4.6% in humans and 6.5% in primates. The difference in equivalent diameters (Ødiff) was higher for human and the surface area of old human capsules shrunk (SS) more than that of young primates showing presbyopic human eyes having a good elastic reserve.

 

 

^{Although the number of eyes is small and an age match between species was not achieved, the elasticity of the presbyopic human lens capsule does not seem to differ from that of younger primate lenses known to accommodate over 10D. The large difference in capsule surface between filled and empty lens is proof of a substantial endolenticular pressure regardless of age.}

 

: NIH EY14225; FL Lions Eye Bank; Aust Govt CRC Scheme; NIH center grant P30–EY014801; Research to Prevent Blindness; Henri and Flore Lesieur Foundation; N. Kenyon PhD, P. Gullett DVM, D. Rothen DVM.

 

 

Keywords: cataract • anterior chamber