Glaucoma diagnosis is currently based on opportunistic case finding, which makes the case for up to 50% of patients remaining undiagnosed. Diagnostic technology has been deemed efficient in diagnosing, but cost and (hospital) location acts as a barrier for effective screening for this asymptomatic disease with a low population-based prevalence~Portuguese National Strategy for Visual Health, published in 2018 asks for a pilot study aimed at a one-time intervention at the primary care setting at the age of 60 years to do both an optic disc analysis and an intraocular pressure (IOP) measurement as a screening system for glaucoma~Two Portuguese centers have applied for this pilot. An urban-based center (Lisbon) and a countryside center (Minho) will conduct an invitation-based screening for those registered in their global primary care area. Age range was increased to 55 to 65 to capture a spectrum of data, enabling to later refine the target population.~Screening Intervention will be the same in both centers. Both will assess reasons for undergoing or rejecting screening and demographic and ophthalmological-related parameters, including glaucoma family history and a known personal glaucoma diagnosis. IOP will be non-invasively checked by rebound tonometry and optic disc retinographies will be performed on both centers. The Minho arm will additionally perform an optical coherence tomography (OCT) on all subjects.~Decision to refer will be made on one (or both) two findings:~IOP of 24mmHg or higher~referrable glaucoma~The Lisbon arm will use an Artificial intelligence (AI) system to rank the retinography findings into a binary referrable vs non-referrable system, based on a pre-defined threshold (0.73).~The Minho arm will base their referral on the existence of optical coherence tomography (OCT) retinal nerve fibre layer abnormality (defined as one sector thickness being outside normal limits)~Subjects flagged as referrable will be sent to the hospital Glaucoma Clinic, where functional and structural examinations will be performed and a standard of care clinical decision will be made by the glaucoma expert.~A reading center, with two masked experts, will be established to determine an unbiased ground truth for the comparison analysis. Reading center will conduct analysis on 3 tier level:~First round will include masked fundus pictures of all recruited subjects from both centers (both positive and negative referrals).~Second Round will include all subjects from Minho arm, who will have both fundus picture and OCT data.~Third round will include data analysis from all positive referrals from both arms, which includes all clinical data from the CRF plus all hospital exams (excluding clinical impression).~Outcomes of the reading center will be twofold:~1. Glaucoma diagnosis label~normal~glaucoma suspect~definite glaucoma (which implies a glaucomatous visual field) 2) Score (0-100) of likeliness of definitive glaucoma Disagreements on any category will be solved by a third masked referee (in the case of the scoring system, a difference larger than 10% would be considered a disagreement)
Two primary care-based screening systems will be used to identify subjects with referrable glaucoma to hospital care.~Subjects between 55 to 65 years old living in two primary care areas (urban area in Lisbon ; countryside setting in Minho) will be invited to a one-time assessment of optic disc and intraocular pressure (IOP).~Criteria for referral will differ between centers, with one arm (Lisbon) using an artificial intelligence (AI) reading software of the optic disc picture, the other (Minho) will base their referral based on optical coherence tomography (OCT) retinal nerve fibre layer abnormality.~A masked reading center will be established to set the ground truth for diagnosis.~This pilot screening trial will explore the level of agreement between both systems as well as their cost effectiveness and identify diagnostic composite scores that could maximize the screening process. Secondary analyses will include the identification of population characteristics that increase effectivity of screening process as well as determining the population less likely to adhere to screening programmes.