Posters

Objective methods to measure the depth-of-focus of ophthalmic surgical microscopes

Poster Details

First Author: J. Schwiegerling UNITED STATES

Co Author(s):    R. Dimalanta                    

Abstract Details

Purpose:

The purpose of this study is to develop and demonstrate objective and reliable means for measuring the perceived depth of focus for surgical microscopes.

Setting:

University of Arizona Optical Sciences and Ophthalmology

Methods:

The depth of focus (DOF) for a selection of ophthalmic surgical microscopes (Alcon LuxOR; Zeiss 700 and OPMI; Leica M820) was assessed. Images of a target with a calibrated ruling pattern are captured through the microscope’s objective lens through one ocular and processed to extract DOF information. The sharpness range is calculated using the Full Width Half Maximum (FWHM) dimension of each ruling with a threshold chosen to define the boundaries of the DOF and converted to a physical distance. The measured DOF is compared across the microscope platforms and accounts for differences in lens design.

Results:

At approximately 7x magnification, the LuxOR with a 200 mm working distance lens objective had a DOF of 6.58mm. The Leica 820 with a depth enhancement turned on had a DOF of 5.98mm. The Zeiss OPMI with a depth enhancement turned on had a DOF of 5.54mm. Additional results of these microscopes set at various configurations for use will be presented.

Conclusions:

The DOF of surgical microscopes varies across design. We have developed an objective means of measuring DOF. Based on our results, DOF is enhanced by using illumination in front of the objective lens. DOF enhancement in some microscopes may also be achieved through reducing the pupil size which may dim the overall image. It was determined that the DOF was highest for the LuxOR microscope using its 200mm objective set at equivalent magnifications amongst all systems tested.

Financial Disclosure:

One or more of the authors is employed by a forNONEprofit company with an interest in the subject of the presentation, One or more of the authors research is funded, fully or partially, by a competing company