Fundoscopic / Ophthalmoscopic Exam
The retina is the only portion of the central nervous system visible from the exterior. Likewise the fundus is the only location where vasculature can be visualized. So much of what we see in internal medicine is vascular related and so viewing the fundus is a great way to get a sense for the patient’s overall vasculature. But the fundoscopic exam can discover pathological process otherwise invisible, examples are plentiful, and include recognizing endocarditis, disseminated candidemia, CMV in an HIV infected patient, and being able to stage both diabetes and hypertension.
Types of Opthalmoscopes
Traditional Direct Ophthalmoscope
PanOptic Direct Ophthalmoscope
The aperture/filter dial allows the opthalmoscope to be used for different purposes.
Large/Medium/Small light source: Ophthalmoscopes usually have 2 or 3 sizes of light to use depending on the level of pupil dilation. The small light is used when the pupil is very constricted (i.e. well lit room, no pupil dilators used). The large light is best if using mydriatic eye drops to dilate. Most commonly in a dark, non-dilated pupil, the medium sized light is used.
Half light: If, for example, the pupil is partially obstructed by a lens with cataracts, the half circle can be used to pass light through only the clear portion of the pupil to avoid light reflecting back
Red free: Used to visualize the vessels and hemorrhages in better detail by improving contrast. This setting will make the retina look black and white.
Slit beam: Used to examine contour abnormalities of the cornea, lens and retina.
Blue light: Some ophthalmoscopes have this feature that can be used to observe corneal abrasions and ulcers after fluorescein staining.
Grid: Used to make rough approximations of relative distance between retinal lesions.
The focusing wheel is the common source of confusion and leads to decreased use of the ophthalmoscope. However, this dial is really VERY easy to use! See below to understand how the focusing wheel works for any direct ophthalmoscope (including the regular ophthalmoscope and the PanOptic).
Technique --> Finding the Retina
- Darken room, ask patient to look at the same point as far as possible in the room (this will help to dilate the pupil).
- Wedge scope against your cheek with hand and then head/hand/scope should move as one unit.
- Use your right hand & your right eye to look at the patient’s right eye. (Less important if using the PanOptic.)
- Look through the ophthalmoscope, if you are nearsighted and have taken off your glasses, you may need to adjust the focusing wheel towards the negative/red until what you see at a distance is in focus.
- Direct the ophthalmoscope 15 degrees from center and look for the red reflex (see video). Simply follow the red reflex in until you see the retina. If you lose the red reflex, come back until you find it again and repeat.
- To look around the retina using a traditional direct ophthalmoscope, you should "pivot" the ophthalmoscope, angling up, down, left and right. If using the PanOptic, you can slightly "pivot" or ask the patient to look up to see upper retina, down to see lower retina, medial to see medial, latereral to see lateral and finally to look at the light to visualize the macula.
Dilating the Pupil
Mydriatic drops. Dilate one eye when you start your H&P and by the time you are done you will have a good look. In general Tropicamide is considered the safest.
- Parasympathetic antagonists: paralyze circular muscle of iris (mydriasis) and the ciliary muscle (loss of accommodation).
- Tropicamide: 1-2 drops (0.5%) 15-20 minutes before exam; may repeat every 30 minutes PRN. Individuals with heavily pigmented eyes may require larger doses.
- Cyclopentolate:1 drop of 1% followed by another drop in 5 min; 2% solution in heavily pigmented iris.
- Atropine: (1% solution): Instill 1-2 drops 1 hour before the procedure.
- Homatropine:1 drop of 2% solution immediately before the procedure; repeat at 10 min intervals PRN.
- Sympathetic agonists:
- Phenylephrine: 1 drop of 2.5% or 10% solution, may repeat in 10-60 min PRNs
- Contraindications: head injury requiring monitoring
Want more information on the use of mydriatic agents for the internist? Please look up this great article that reviews data on the risk of precipitating acute glaucoma: Pandit, RJ and Taylor R. Mydriasis and glaucoma: exploding the myth. A systematic review. Diabet Med. 2000 Oct;17(10):693-9.
Clinical Images of the Retina
Vessels emerge from nasal side of disc. Arteries are narrower than veins.
Pathological Optic Cupping
Note cup-to-disc ratio at least 0.8 (physiologic limit of 0.5).
Optic Disk Edema
The optic disc is elevated and its surface is covered by cotton wool spots (damaged axons) and flame hemorrhages (damaged vessels). Four I's: increased intracranial pressure (papilledema), infarction, inflammation, infiltration (by cancer).
The first picture below was taken simply by holding smartphone in front of the Panoptic opthalmoscope!
Arterio-Venous (AV) Nicking
Chronic hypertension stiffens and thickens arteries. At AV crossing points (arrow) arteries indent and displace veins.
Cotton Wool Spots
Caused by microinfarcts. Exploded ganglion cell axons extrude their axoplasm into retina. Long DDx: hypertension, diabetes, HIV, severe anemia or thrombocytopenia, hypercoagulable states, connective tissue disorders, viruses, and others.
Emboli and Infarcts
Small fleck a ‘Hollenhorst’ plaque caused from platelet/fibrin/cholestorol embolus. Resulting in an infarct (gray area above and right of the plaque).
Pale-centered hemorrhage. Caused by several conditions, but usually bacterial endocarditis. This image was from a patient with staph endocarditis.
Key Learning Points
- Learn the settings of the direct opthalmoscope
- Learn the technique of the direct opthalmoscope (see video)
- Overview of pupil dilation
- Review common retinal findings that medical internists should know
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