The invention describes several embodiments of an adapter which can make use of the devices in any commercially available digital cameras to transform the digital camera into a fundus camera for inspecting the back of the eye, or into a microscope. The camera adapter is adapted to be placed between the camera device and the object. The devices in the camera being used are at least its optical source, photodetector sensor, memory, shutter and autofocus. Means in the adapter are provided to employ these devices and allow camera to operate its autofocus capability and its different color sensors. Methods of investigation of an object are also presented of using the adapter to transform the camera into an imaging instrument, where the effect of adjustments of elements inside the adapter are guided by the displaying screen of the camera.