Measuring axial length of the eye from magnetic resonance brain imaging

Stewart J. Wiseman, Andrew J. Tatham, Rozanna Meijboom, Graciela Muniz Terrera, Charlene Hamid, Fergus N. Doubal, Joanna M. Wardlaw, Craig Ritchie, Baljean Dhillon, Tom MacGillivray
BMC Opthamology (2022)

The human eye supplies measurements that are increasingly used as biomarkers in studies of cardiovascular, cerebrovascular and neurological disease. One such measurement is “axial length” that essentially represents the size of the eye. Often, the length of the human eye is measured using an ophthalmological instrument, but not all studies have access to such specialized equipment. Studies of brain disease typically have access to brain scan data. The PREVENT Dementia programme has access to both. Hence, in 93 cognitively-healthy individuals from the programme (age 40 to 59 years), we measured axial length from brain MRI scans using three different image analysis software tools and compared results of our measurements to the gold standard measurements from the ophthalmic instrument. We concluded that axial length of the eye obtained from brain MRI is not a replacement for the precision of specialized ophthalmic equipment, but, in its absence, it could provide sufficient accuracy to act as a proxy.