Purpose:
To image the interior ultrastructure of the lens using Atomic Force Microscopy (AFM).
Methods:
Porcine eyes were retrieved from an abattoir, placed in a bag filled with saline, and shipped to the laboratory overnight. Human eyes were retrieved from a local eye bank. Upon arrival, the lenses were extracted from the whole globes and placed in 10% formalin for one week. One porcine and one human lens were prepared for imaging by sectioning them from the anterior pole to the posterior pole. Each segment of the sectioned lenses was then viewed under a light microscope (10X) to verify that the lens was cut smoothly and that the native, internal structure of the lens remained intact. The lens halves were then carefully embedded within a 5% Agarose gel in a Petri dish to stabilize the sample for imaging. A commercial Asylum AFM was used to image the collagen structure of the lens at the nanoscale level. The images were obtained in contact mode, in which the cantilever tip is kept in continuous contact with the sample surface, maintaining constant cantilever deflection while scanning. The piezoelectric mechanism applies vertical position corrections to keep this deflection constant, thereby mapping the actual three-dimensional topography of the sample surface. The imaging was performed with the lens submerged in balanced salt solution.
Results:
AFM was successful in providing high resolution images of the internal structure of the porcine lens (Figure 1) and human lens. Repetitive layers of long lens fiber cells were seen in the images.
Conclusions:
AFM can provide high-resolution, quantitative images depicting the densely packed fibers of the lens.
Figure 1. Resulting AFM image. Deflection image of porcine lens.
Keywords: anatomy • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • topography