carbonic anhydrase inhibitors lessen aqueous humour production by interfering with an enzyme, carbonic anhydrase, involved in sodium and fluid transport in the ciliary body. Topical dorzolamide 2% eye drops are generally used as adjunct therapy with other drugs to lower the Iop (Sharts-hopko and glynn-milley 2009). This involves making a clinical decision about what level of Iop is considered to be low by the healthcare professional treating the person. The aim is to minimise or arrest disease progression or onset and avoid disability from sight loss within a person’s expected lifetime (nIce 2009)..