Scotopic microperimetry: evolution, applications and future directions

For many inherited and acquired retinal diseases, reduced night vision is a primary symptom. Despite this, the clinical testing options for spatially-resolved scotopic vision have until recently been limited. Scotopic microperimetry is a relatively new visual function test that combines two-colour perimetry with fundus-controlled perimetry performed in scotopic luminance conditions. The technique enables spatially-resolved mapping of central retinal sensitivity alongside the ability to distinguish between rod and cone photoreceptor sensitivities. Two companies produce commercially available scotopic microperimeters – Nidek (Nidek Technologies Srl, Padova, Italy) and CenterVue (CenterVue S.p.A., Padova, Italy). Scotopic microperimetry is a promising technology capable of detecting changes in retinal sensitivity before changes in other measures of visual function. Scotopic microperimetry is a promising functional biomarker that has potential as a useful clinical trial outcome measure. In this review, we summarise the evolution and applications of scotopic microperimetry, discuss testing options, including testing grid selection and dark-adaptation time and threshold sensitivity analyses.