The optic fundus can be viewed with a variety of instruments, but the direct ophthalmoscope is used for screening.
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.
To perform direct ophthalmoscopy, select the large beam aperture, set your index finger on the dioptric dial and set the dial to zero. If the patient's pupils are very small, switch to the small lens aperture. Use your right eye to examine the patient's right eye, and your left eye to examine the patient's left eye. Here is how to do direct ophthalmoscopy.
To find out what the main optic fundus abnormalities look like, go to the review topic Optic Fundus Signs.
To find out how often you should perform this ophthalmic screening examination on asymptomatic patients, see Exam Frequency.