Broadbent, Deborah M, Sampson, Christopher J, Wang, Amu, Howard, Lola, Williams, Abigail E, Howlin, Susan U, Appelbe, Duncan, Moitt, Tracy, Cheyne, Christopher P, Rahni, Mehrdad Mobayen, Kelly, John, Collins, John, García-Fiñana, Marta, Stratton, Irene M, James, Marilyn, Harding, Simon P, "Individualised screening for diabetic retinopathy: the ISDR study—rationale, design and methodology for a randomised controlled trial comparing annual and individualised risk-based variable-interval screening", BMJ Open, 2019