Patent ID: 8366704

Claim:
An apparatus for applying radiation to a subject's retina, comprising: a radiation source for generating a radiation beam having one or more wavelengths suitable for absorption by retinal pigment epithelial cells, at least one optical component for directing the beam onto the retina, a scanner optically coupled to the source for controllably moving the beam in two dimensions to scan the beam over the retina, and a controller in communication with the scanner to apply control signals thereto for adjusting movement of the beam to illuminate a plurality of retinal locations according to a scan pattern, wherein the controller is capable of operating the scanner in any of at least two scan modes, one of the scan modes being suitable for selective targeting of retinal pigment epithelial (RPE) cells and another scan mode being suitable for causing thermal photocoagulation in the retina, wherein the controller operates the scanner in the selective targeting mode by scanning with a beam characterized by parameters within a therapeutic window defined by a ratio of an ophthalmoscopic ED 50 fluence to an angiographic ED 50 fluence for a selected beam dwell time, wherein the ophthalmoscopic ED 50 fluence is a fluence at the selected beam dwell time that results in ophthalmoscopically visible indicators of photocoagulation of the retina, and the angiographic ED 50 fluence is a fluence at the selected dwell time that results in indicators of selective damage to RPE cells that are visible using angiography, but are not ophthalmoscopically visible; wherein the controller operates the scanner in the selective targeting mode when the ratio has a value greater than about 1.5; wherein the controller operates the scanner to produce a fractional illumination pattern over the retina in which a fraction of retinal pigment epithelial cells within the retina are illuminated, the fractional illumination pattern comprising a plurality of treatment portions of the retina that are exposed to the radiation beam, and wherein each treatment portion is surrounded by an untreated portion of the retina that is not exposed to the radiation beam; and wherein the fractional illumination pattern comprises a plurality of beam spots on the retina, each beam spot corresponding to one of the treatment portions.