Dilating the Pupils
Examining the fundus through the undilated pupil is a challenge because the pupil is normally quite small and will further constrict when you shine the ophthalmoscope beam into it. If you really want to see anything, you should dilate the pupils.
The ideal pupil-dilating agent is tropicamide 1%, a parasympatholytic. Unfortunately, tropicamide will also paralyze accommodation, which is a nuisance in individuals under age 50 because they will not be able to read for several hours. A reasonable and safe alternative is phenylephrine 2.5%, a sympathomimetic agent. However, its dilation effects are modest and delayed for about 30 minutes.
If you choose not to dilate the pupils, your technique must be very, very good. Here is how to get the best view using direct ophthalmoscopy.