Confocal scanning infrared laser ophthalmoscopy for indocyanine green angiography

We used indocyanine green to study wavelength-optimized confocal scanning infrared laser angiography in patients with retinal and choroidal disease.

A confocal scanning laser ophthalmoscope with an excitation wavelength of 795 nm was operated both in tight and wide confocal imaging modes. We examined 77 subjects with and without retinal and choroidal disease (including diabetic retinopathy, age-related macular degeneration, and subretinal neovascularization).

The scanning laser ophthalmoscope allowed acquisition of images, in the wide confocal imaging mode, of the retinal circulation and late leakage sites without late injections of dye to outline the retinal vasculature. In the tight confocal imaging mode, optical subtraction of the light contribution of the retinal circulation allowed examination of the choroidal circulation, and vice versa. The wide confocal mode appears equivalent to other scanning laser ophthalmoscopes in recording images from retinal and choroidal layers.

There are three differences between the confocal scanning laser ophthalmoscope and conventional instruments. First, the late images allow excellent visualization of the retinal circulation without a landmark injection. Second, confocal imaging allows optical subtraction of retinal circulation when focusing on the choroid and vice versa. Third, the instrument acquires and processes all data digitally, is personal computer-based, is compact, operates with a mouse-driven graphical user interface, and allows easy data exchange with conventional software. With further modifications in software and hardware, this device offers the possibility of producing a three-dimensional map of the retinal and choroidal vasculature.