SAN DIEGO – Like choosing a cell phone, stereo system, or new car, shopping for a microscope suitable for a Mohs surgery practice can be a delicate balance between what is needed, what is wanted, and how much money there is to spend.
Consumer Reports doesn’t have a special Mohs edition to help out on the microscope hunt, but Dr. Kenneth G. Gross offered his perspective on must-haves, don’t-wants, and "highly desirable features" to look for in a microscope designated for the special needs inherent in Mohs.
For starters, he emphasized that an appropriate microscope is a necessity, not a luxury.
"That little student microscope you used in medical school is really not the kind of microscope you want to use in a Mohs practice. You don’t bring a knife to a gun fight," he said at a meeting sponsored by the American Society for Mohs Surgery.
Dr. Gross, a dermatologic surgeon practicing in San Diego, explained that several competitive companies market technical microscopes that work well for Mohs and that all make quality products. He stated no personal preference but recommended shopping for a microscope that contains certain specifications, no matter the manufacturer.
Binocular or Trinocular?
Mohs surgeons really need a microscope with a teaching head – a binocular design – and ideally, the addition of a trinocular scope for photography.
A dual head is valuable not only for teaching or consultation with a resident, colleague, or pathologist, but it also allows for demonstrating to a technician the errors that can thwart a complete and accurate view of a specimen.
A third head for a camera is not 100% necessary, but is very nice to have, according to Dr. Gross.
"Photography is so easy nowadays, it is really stone simple. Everything is through the viewfinder and through the lens," automatically optimizing the F-stop, speed, and color balance.
"That little student microscope you used in medical school is really not the kind of microscope you want to use in a Mohs practice."
"Really, there’s no trick to it," said Dr. Gross. "You just attach a digital camera on top and shoot."
Point it Out
An adjustable, lighted pointer further assists communication and identification of focal regions on a slide.
"If there’s something I don’t see, [the pathologist] can flip on the pointer and say, "There you are, man. There it is."
Focusing on Lenses
Objective lenses, those closest to the specimen, come in three quality levels, and the middle level is acceptable for Mohs, according to Dr. Gross.
The lowest power objective lens should be no bigger than a 2.5x; a 2x is preferable. A 1x or 1.5x is fine as well, but not necessary, he said. With a 2.5x objective lens, "You can orient yourself to a pretty big specimen ... without getting lost."
He compared the view of a large specimen with a 10x objective lens to looking at ink dots and then trying to figure out how they combine to form letters on a book page.
Nose pieces hold five objective lenses, with a 2x, 4x, 10x, 20x, and 40x of middle-quality a good selection.
"You do not need an oil immersion lens on your microscope," he said.
Proper lighting with different lenses is achieved by using swing-out condensers, the best of which "clunk" into place like a solid car door.
The ones that freely slide from side to side are "kind of a piece of junk in my opinion," he said, "because they get out of focus easily."
When it comes to ocular lenses, pony up for the focusable, highest-quality, wide-angle options available, Dr. Gross said.
Each person viewing the specimen should be able to separately focus the image to accommodate individual differences in visual acuity.
Angle for Tilt Heads
Opting for a system with tilt heads isn’t imperative, but is wise if more than one doctor is sharing the microscope, according to Dr. Gross.
"Unless you’re identical twins, you’re going to [have one doctor who is] taller or shorter, sits up straight or slumped, use[s] different style chairs. If you have tilt heads, they’re really easy to adjust."
You can economize, though, by foregoing an option that allows the microscope heads to push in or out. "That’s a waste of money," he said.
Dr. Gross said he had no financial disclosures with regard to any company that manufactures or maintains microscopes used in Mohs surgery.