Coloured halos are not seen in acute anterior uveitis and this is one of the differentiating points between acute anterior uveitis and acute angle closure glaucoma Tetracycline does not cause coloured halos.Important drugs causing coloured halosAmiodarone                                                            Amyl nitrite                                                                             Chloroquine                                                                  Chlorpromazine  Cortisone      Digoxin  Fluphenazine   Hydrocortisone  Oral contraceptives  Trimethadione  Prednisolone Promethazine Sildenafil Triflupromazine Water (sterile)