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The portable 'hand-held’ digital ophthalmoscope: a new type of high resolution hand held retinal imaging instrument

This paper discusses the resolution required to provide a ‘new affordable generation’ of ophthalmic instrumentation for imaging the retina. The paper describes the evolution of the direct ophthalmoscope as a device that can capture digital images of sufficient detail and contrast such that they both medically useful and can form a wide-field composite image of the human retina comparable to that of a fundus camera. During the early stages of diagnosis, medical practitioners often rely on an ophthalmoscope for making a first inspection of the retina. It is an instrument which has taken considerable time to change from human observation to a digitally processed image. There is a good reason for this, the instrument relies on the near to diffraction limited imaging ability of the human eye and the ability of the user to scan the instrument over the retina to create a high resolution contiguous mental image. Whereas the more sophisticated instruments such as the fundus camera relies on conventional imaging technology to make a digital imaging record of the retina. The digital ophthalmoscope described creates an image with 5μm resolution over the whole retina. This paper discusses the comparison of the of resolution quality which can be achieved using digital storage of retinal imaging. Two devices will be considered the direct ophthalmoscope, which is essentially a hand-held portable device for direct inspection and the fundus camera. The analysis argues that currently the resolution of digital camera technology used in the fundus camera, particularly those used for mobile scanning, limits its optical diagnostic power. Whereas, a digital ophthalmoscope using well tried imaging stitching software and digital processing provides an alternative higher imaging resolution, hand-held portable alterative.