Comparison of Modern Super Wide Field Microscopy Systems in Mohs Surgery

October 2021 | Volume 20 | Issue 10 | Original Article | 6083 | Copyright © October 2021


Published online September 15, 2021

Michael S. Dent MD, C. William Hanke MD MPH

Laser and Skin Surgery Center of Indiana, Indianapolis, IN

Abstract
Microscopic interpretation of frozen tissue sections is fundamental to Mohs micrographic surgery. Mohs surgeons spend a significant portion of their day at the microscope. Eye strain and fatigue, in addition to musculoskeletal strain, may increase the risk of interpretation errors as well as musculoskeletal injury.3,4,5,7 Advances in microscope systems have allowed for more efficient and reliable reading of slides as well as decreased physical strain. In particular, the advent of super wide field (SWF) microscopy, which includes lower power objective lenses as well as wider eyepieces, allows for a much larger area to be viewed, decreasing eye strain.2,5 Also, more ergonomically designed systems help to decrease musculoskeletal fatigue and injury.7 In an update to an article from Goldsberry et al, that compared older SWF microscope systems,1 we review three newer systems for comparison: Leica DM2500, Nikon Ci-L, and Olympus Bx53 (Figure 1.) Each system reviewed demonstrates ergonomic design and super wide fields of view, allowing for efficient interpretation of tissue and decreased eye strain and musculoskeletal strain compared to older systems. The Nikon Ci-L had the largest possible VFA at 490.87 mm2, 40% more area than the Olympus and 56% more area than the Leica.

J Drugs Dermatol. 2021;20(10): doi:10.36849/JDD.6083

INTRODUCTION

Mohs micrographic surgery is the treatment of choice for large, aggressive, recurrent, or poorly defined skin cancers, as well as skin cancers in functionally or cosmetically sensitive areas. The reasons for this include the high cure rate, the cost-effectiveness of treating with local anesthesia in the outpatient setting, the superior aesthetic and functional results of repairing the smallest possible defect, and perhaps most importantly, the ability to precisely clear 100% of the tissue margin using frozen section processing and microscopic evaluation. Mohs surgeons end up spending considerable time and effort in interpreting slides. Therefore, we wanted to evaluate modern microscope systems that incorporate SWF eyepieces, low magnification objectives, and ergonomic designs. We evaluated the performance of each system for 1–2 weeks and report our findings.

RESULTS

First, it is important to understand the basics of SWF microscopy and how significant it is to the efficient interpretation of frozen sections. The viewable field area (VFA), also known as the field of view, is simply the actual area of what the microscope user is visualizing when looking into the scope through a particular lens. The larger the VFA, the more data one can process, with less time, less eye movement, and less slide manipulation. A larger VFA allows for a more efficient overall experience for the Mohs surgeon. In order to determine the VFA, we need to know the field number (FN) associated with the microscope as well as the magnification objective (MO) for a particular lens. The FN represents the diameter of the largest VFA possible on a particular microscope eye piece. Dividing the FN by the MO gives the view field diameter (VFD), which is the actual diameter of the VFA for a specific FN and MO. We are basically finding the area of a circle (πr2) when calculating the VFA. Calculations are as follows:

View Field Diameter = Field Number/Magnification Objective
Viewable Field Area = π*(View Field Diameter/2)2


The VFA varies based on the FN and MO of the eyepieces and lenses available for each microscope (Table 1.)1 Modern SWF systems incorporate higher FN’s (25mm+) and lower MO’s (1-2x) compared with older wide field systems (FN 18–22 mm, lowest