Clinical guidelines are acknowledged to be the highest level of evidence in Evidence Based Medicine. They are defined by the Institute of Medicine (2011) as "statements that include recommendations, intended to optimize patient care, that are informed by a systematic review of evidence and an assessment of the benefits and harms of alternative care options"
Clinical or practice guidelines can be located in many places. Some suggestions are shown below.
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Consensus report, Institute of Medicine. Clinical practice guidelines we can trust. March 23, 2011. http://www.iom.edu/Reports/2011/Clinical-Practice-Guidelines-We-Can-Trust.aspx
Many Practice Guidelines are created by and hosted on Association websites. For example Optometry Australia produce Practice Guides on a number of eye related topics.
These can be found by searching the Internet, or within specific association webpages