If there’s one tool every pathologist uses on a near-daily basis, it’s the humble light microscope. But have you ever considered this instrument’s role in your potential for exposure to UV light?
Until recently, I would have said “no.” Now, I’ve done some investigation – with surprising results.
We have a range of objective microscope lenses available to us. In general, achromat lenses are the most basic, whereas plan apochromats are often considered superior. My inquiries revealed that plan apochromats have the highest levels of UV light transmission – including to the eyes of the user. This is confounded by the fact that most LEDs used in modern microscopes emit some UV light. What does this mean for regular microscope users? To double-check my observations, I contacted customer support at a prominent microscope provider, who sent me the following reply:
“I have reviewed your concern on UV transmission through various objective lenses. It is true that UV is harmful to our eye and high-grade objective lenses have higher transmission than low-grade lenses. If you are not using a camera or imaging device for the microscopy, then you may use low-grade lenses with any eyewear. If you are using a camera or imaging device, you can use high-grade lenses and rely on the images from the device. This method will provide better imaging quality.”
I was astonished to find that these high-grade lenses, for which we pay a premium, actually come with a higher risk of harm to the eyes. To further verify my concerns, I examined the data on plan apochromat lenses from several major manufacturers. All claimed suitability for use with fluorescence in UV light – a necessity for many applications, but also an indication of higher UV transmission. Are we overlooking a potential source of harm in our laboratories?
In my view, UV light exposure is overlooked when we buy our microscope objectives – and we need more information. I strongly recommend a practical study on the amount of UV light to which we are exposed while using microscopes in routine clinical settings. Until that is done, I recommend that we all wear UV protective eyeglasses when using the microscope – and I look forward to the day when every lens has minimal UV light transmission or, at the very least, the option of a UV filter.
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