An adhesive composition for joining optical components is described. The adhesive composition comprises at least one epoxy resin, a visible light photo-initiating system comprising at least one of a cationic photoinitiator and a sensitizer, a polyol and at least 50wt.% of a nano particle filler. The visible light photo-initiating system includes at least one of a cationic photoinitiator and a sensitizer and the nano particle filler comprises a first nano particle having a first nominal size and a second nano particle having a second size. The adhesive composition has a refractive index between1.44 and 1.47 and a dn/dT of less than -2E-4 when cured.