The Direct Ophthalmoscope is used to view the ‘Fundus’ or posterior portion of the eye. The image seen is magnified 16 times and a series of up to 20 lenses can be switched in to focus and correct for the refractive errors of both the patient and the medical student!
The lenses are normally Convex (+ve and black) which correct long-sight or Concave (-ve and red) which correct short-sight. After any refractive correction, moving more -ve will shift the focus from the front of the eye towards the back. To make a meaningful comment the pupil should also be dilated with drops, otherwise only 15% rather than 50% of the fundus will be seen.
- Ensure the room is as darkened as possible.
- Ask the patient to keep looking at a distant object (e.g. the corner of a door) even if you get in the way.
- If you wear glasses or contact lenses, it is best to keep them on.
- You must always look at the patient’s RIGHT eye with your RIGHT eye whilst the ophthalmoscope is held in your RIGHT hand and vice-versa with the other eye.
- Look for the RED REFLEX with the Ophthalmoscope set to 0, and at a distance of about an arm’s length. The pupil will glow red from the reflection of the retina. You will see any opacities in the lens (Cataracts) as defects in the red reflection.
- From here, move towards the pupil until you are only about an inch or two away. Rest your free hand on their forehead to steady yourself and lift their eyelid if needed. Don’t forget to breathe!
- Approach at the same level as the patient’s gaze, but come in at about 20○ to the side to see the OPTIC DISC, as it is set slightly medially. You will need to use the lenses to focus.
- Look for a sharp disc margin, yellowed colour and a ratio of the pale centre (cup) to the total width of no more than 0.3.
- Follow out the large BLOOD VESSELS in their four directions.
- Look around at the general state of the surrounding RETINA for haemorrhages, exudate or raised masses.
- Finally end by reducing the brightness on the ophthalmoscope and asking the patient to look directly at the light. You will then be able to see the MACULA and FOVEA. Don’t linger for too long!