The dataset comprised 2265 patients with diabetes aged 40 years and older, recruited from a population-based cross-sectional study conducted in South India (SNDREAMS).
17 The detailed methodology has been described elsewhere. In summary, a written consent was obtained from each participant for sample collection, and they underwent various health measurements and completed questionnaires. Collected data included age, race/ethnicity, sex, current smoking status, and medical and ocular history, as reported via questionnaires to social workers. General physical examinations recorded height, weight, waist and hip circumference, blood pressure, and heart rate. Comprehensive eye examinations included vision assessment, objective and subjective refraction, corneal examination, slit lamp evaluation of the anterior segment, Goldmann applanation tonometry for intraocular pressure measurements, and lens opacity assessments. For posterior eye segment evaluation, dilated 45-degree 4-field retinal fundus images were taken using a VISUCAMlite (Carl Zeiss, Jena, Germany) by 2 experienced technicians. Laboratory analyses included complete blood count and Hb concentration levels, analyzed using the Merck Micro Lab 120 semi-automated analyzer. Hb levels were measured with a calorimetric hemoglobinometer, packed cell volume with the capillary method, and glycosylated Hb fraction using the Bio-Rad DiaSTAT HbA1c Reagent Kit.
17 Anemia was defined per World Health Organization guidelines as Hb levels below 12 g/dL for women and 13 g/dL for men.
18 Inclusion criteria required blood tests to be conducted within 2 weeks of fundus imaging, with no transfusion therapy or blood donation between imaging and blood measurement. Fundus images that were either blurred or with artifacts due to vitreous hemorrhage or severe cataracts were excluded. For external validation, a total of 255 UWF OPTOS (Daytona; Optos PLC, Dunfermline, United Kingdom) images, along with corresponding clinical and hematological data, were collected from Sankara Nethralaya, India. Additionally, the images were cropped to extract the central area from the original UWF fundus images, generating a field of view similar to that used in our developed model. The study received approval from the Institutional Review Board at Vision Research Foundation, Sankara Nethralaya, Chennai, and the Human Research Ethics Advisory Panel of the University of New South Wales ensuring adherence to the Declaration of Helsinki principles.