Compact Shadowphotogrammetry System for Measurement of Isolated Lens Shape

Abstract

Purpose: : To develop a compact low-cost table-top digital shadowphotography system which produces undistorted images of the lens profile.

Methods: : A shadow-photogrammetric system optimized for isolated lens contour imaging was designed. The system uses two optical imaging paths to produce sagittal and coronal views of the lens. Each imaging path uses a telecentric white-light LED illumination system and folding mirrors which direct the beam to a common lens objective. The objective creates an image of the lens plane on the sensor of a digital camera. A positioning and mounting stage was designed to allow precise alignment and centration of the lens immersed in preservation medium (DMEM). To avoid distortions the immersed lens is supported by suture wires. The system was constructed using rapid manufacturing techniques of stereolitography using clear resins and polyjet. The resolution of the system was quantified using an AirForce resolution resolution target. Thus far, the system has been used on 4 monkey isolated lenses.

Results: : The telecentric imaging system produced high contrast images of the lens with a resolution of 32 lp/mm, corresponding to 13.4 micrometers in the plane of the lens, and a large depth of field. The resolution was sufficient to visualize the zonular attachment on coronal views of the lens. Undistorted contours of the whole lens including the equatorial region were obtained on all lenses.

Conclusions: : The study demonstrates the feasibility of acquiring undistorted shadowphotographic images of the whole contour of the isolated crystalline lens and of the zonular attachments using a low-cost table-top optical imaging system.Support: NIH Grants 2R01EY14225, P30EY14801 (Center Grant); the Florida Lions Eye Bank; Dr Rakhi Jain, AMO Inc, Santa Ana, CA; an unrestricted grant from Research to Prevent Blindness; Australian Federal Government CRC Scheme through the Vision Cooperative Research; Henri and Flore Lesieur Foundation (JMP).

Keywords: optical properties • imaging/image analysis: non-clinical