Confocal infrared RM imaging of macular diseases

The RM imaging enables investigators to observe the details of deep retinal structures, noninvasively and clearly, by illuminating the fundus with an infrared laser and collecting the scattered light reflected from the retina and choroid through a semicircular and pericentral aperture by a new confocal technique. This allows for a clearer pseudo three-dimensional image, which is a new method of detecting abnormalities in the macula.¹

Some advantages of using the F10 SLO to examine the macula are: non-invasive procedure, short testing time and the entire extent of the macula can be obtained in one image under non-mydriatic conditions.

This report aims to show some macular diseases features in which this imaging method could be helpful.

Drusen

RM imaging has been reported to detect more drusen then conventional color fundus photography.² The drusen borders, by this imaging method are well highlighted, making them easier to manually segment and grade.

The measurements of drusen number and area obtained by RM were compared with those obtained using standard colour fundus photography. Drusen number grades were found to be significantly higher using the right (AR) and left (AL) lateral apertures in which the laterally scattered light is captured.

The mean drusen number detection with the AR retromode was almost two times greater than for the colour photographs. Small drusen, as well as drusen more distant from the fovea, were more easily visualized with the AR and AL retromodes. The AR retromode would probably be preferred and recommended in further comparative studies; while drusen appear in an elevated convex shape in the AR, in the AL the conformation seems to be inverted.