Effect of Personal Protection Equipment (PPE) and the Distance From the Eye Piece of Surgical Microscope on the Field of Vision; An Experimental Study.

backgroundDuring the Covid-19 pandemic, otolaryngologists are at risk due to aerosol-generating procedures such as mastoidectomy and need enhanced personal protective equipment (PPE). Eye protection can interfere with the use of a microscope due to a reduction in the field of vision. We aimed to study the effect of PPE on the microsurgical field.

methodsFive surgeons measured the visual field using digital calipers at different power settings. They were done with no PPE, a surgical mask, FFP3 mask (N99), and with the addition of small goggles, large vistamax goggles, vistamax plus a face shield, and only a face shield. The measurements were repeated with rings of 5 mm increments. We also measured the "eye relief" of the microscope which is the ideal distance for maximum field of view.

resultsThere was no major reduction of the field with the surgical or FFP3 mask. But even simple goggles reduced the field up to 31.6% and there were progressive reductions of up to 75.7% with large goggles, 76.8% when a face shield was added, and 61.9% when only face shield was used. The distance rings more than 5 mm also affected the field of view.The eye relief of our eyepiece was found to be 15 mm.

conclusionThe current PPE eye protection is not compatible with the use of a microscope. There is scope for research into better eye protection. Mitigation strategies including barrier drapes and alternative techniques such as endoscopic surgery or use of exoscopes should also be considered.