'Six eyes, not eight'
The brown recluse (Loxosceles reclusa), Sicariidae (formerly placed in a family "Loxoscelidae") is a recluse spider with necrotic venom. Similar to those of other recluse spiders, their bites sometimes require medical attention. The brown recluse is one of three spiders in North America with toxic venom, the others being the black widow and the Chilean recluse.
You may not always be able to count the eyes and some eye pairs are so close together that you might not be able to see both of them, however, the 6 eye pattern of the brown recluse is easy to see with minor magnification. Most spiders can be eliminated as NOT brown recluses simply from this aspect. Be aware that there are spitting spiders (genus Scytodes) (below) which have a similar eye pattern but they do NOT have a violin (plus it has more than one color on its legs and abdomen.
It it is true that a brown recluse has a violin pattern, many non-arachnologists creatively misinterpret many markings on spiders as "violins" and feel that they have found recluse spiders. Therefore, if you can learn to identify your spider as NOT a recluse, you can stop worrying.
Many of the really graphic nasty wounds you see on the internet as recluse bites can also be other conditions like necrotizing bacteria and pyoderma gangrenosum. Ninety percent of brown recluse bites are not medically significant, heal very nicely often without medical. intervention and treatment for most brown recluse bites is simple first aid.
Recluse spiders have six eyes arranged in pairs (dyads) with one median pair and two lateral pairs. Only a few other spiders have three pairs of eyes arranged in this way (e.g., scytodids). Recluses have no obvious coloration patterns on the abdomen or legs, and the legs lack spines The violin marking can vary in intensity depending on the age of the brown recluse spider, with mature spiders typically having dark violin shapes.
BE AWARE & PRACTICE CAUTION!