Ophthalmology is the study of medical conditions relating to the eye.
Scanning Laser Ophthalmoscopy (SLO) marked a change in photographic capture technique which utilized the principle of illuminating only a little spot of the retina with collimated laser light directed through the very centre of the pupil and capturing the reflections from its entire surrounds within the pupil confines.
Optical Coherence tomography (OCT) added a replacement dimension to retinal imaging with the power to develop cross sectional images of retinal tissue to a submicron axial resolution and millimeter penetration using a low coherence interference technique combined with a broadband light. Time-domain initially and later Fourier domain OCT techniques have further improved axial resolution of tissue cross-section.
Adaptive Optics (AO) was originally developed for the sector of Astronomy to get rid of image blurring aberrations induced by wavefronts propagating through Earth’s atmosphere. The invention of the direct ophthalmoscope gave a lift to the study of retinal diseases, with the knowledge of reversibility of rays and paraxial viewing.
A further development was the indirect ophthalmoscope, which allowed rays to make real images using an equivalent system that converged the light into the attention . Unlike imaging of everyday objects, imaging of the retina is limited by the size of the entrance pupil, and the outgoing rays being imaged are restricted by the size of the same exit pupil.