 Study participants will be recruited from patients attending the Ophthalmology Department Outpatients Clinic at St Thomas Hospital, London, United Kingdom who have a diagnosis of glaucoma or OHT ocular hypertension requiring glaucoma drainage surgery. One hundred patients with glaucoma or OHT and where a clinical decision has been made that they need glaucoma surgery will be included in the study such that 100 eyes undergoing surgery will be included together with the contra-lateral untreated eyes that will be used as controls for comparison with the treated eyes. 