Changes in Lens Capsule Thickness During Simulated Accommodation

Abstract

 

Abstract:

 

To determine if the thickness of the crystalline lens capsule changes during accommodation.

 

Anterior and posterior capsule thickness was measured on post–mortem lenses using a non–contact optical system using a focus–detection technique. The optical system uses a 670nm laser beam delivered to a single–mode fiber coupler. The output of the fiber coupler is focused on the tissue surface using an aspheric lens (NA=0.68) mounted on a translation stage with a motorized actuator. Light reflected from the sample surface is collected by the fiber coupler and sent to a photoreceiver connected to a computer–controlled data acquisition system. Optical intensity peaks are detected when the aspheric lens is focused on the capsule boundaries. The capsule thickness is equal to the distance traveled between two peaks multiplied by the capsule refractive index. The precision of the optical thickness measurements was determined to be ±0.5µm. Anterior and posterior lens capsule thickness measurements were performed on 17 monkey (6±2years, range 2–7 years) and 12 human (65±16years, range 42–92 years) intact lenses during simulated accommodation. The ex vivo accommodation apparatus and tissue preparation have been previously described (Parel et al, ARVO 2004, #1724). The mounted sample was placed under the focusing objective of the optical system so that the light was incident on the center pole. Measurements were taken of the anterior lens capsule in the unstretched and the stretched 5mm states. The lens was flipped, and the same procedure was performed for the posterior lens capsule.

 

 

 

^{No significant relationship could be found between lens capsule thickness changes and age.}

 

This study demonstrates that the thickness of the primate anterior lens capsule changes significantly during accommodation.

 

Support: NSF GSF; NIH EY14225; Florida Lions Eye Bank; Vision CRC, Sydney Australia; NIH center grant P30–EY014801; Research to Prevent Blindness.; Henri and Flore Lesieur Foundation.

 

 

Keywords: cataract • microscopy: confocal/tunneling • laser