What is the best spot size fractional treatment?
There are as many opinions as spot sizes. In general, with the correct parameters, slightly difference spot sizes will result in indistinguishable clinical results. It is more or less a utilitarian choice in that larger spot sizes are easier to use for full field resurfacing, and fractional spot sizes are less visible to the eye if they are smaller. Most modern CO2 lasers have diffraction limited beams, and can all provide about the same spot sizes with the proper selection of lenses, so it is usually a deign choice. My preference is to use the largest spot that is aesthetically pleasing. Aesthetic medicine is a subjective field after all. Anything less than 300 µm in diameter seems to blend very well without noticeable spots in a day or two. A side issue is that there is no standard definition used by manufacturers for the spot size specification so comparing lasers with different advertised spot sizes can be misleading. So when comparing spot sizes you need to know if they are defining it as the half power points, the area containing 90% of the energy, the pattern burned on laser paper, or the 1/e2 power points. Are they including the thermal coagulation zone or just the drilled channel, or are they measuring the laser beam itself? The lack of a precise and standard definition leaves a lto of room for marketing.
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