High magnification direct ophthalmoscopy.
The combination of a high minus setting of the ophthalmoscope and an extra positive lens in front of the patient's eye forms a Galilean telescope that increases magnification in direct ophthalmoscopy. The telescope magnification equals the ratio between objective and ocular focal lengths.
D005069:Evaluation Studies as Topic; D007909:Lenses; D019721:Ophthalmoscopes; D055095:Optics and Photonics / Q000295:instrumentation