Learning indirect ophthalmoscopy may be the most difficult and stress-provoking exam technique a new resident faces. The skill is rightfully challenging — indirect ophthalmoscopy proficiency takes thousands of exams. However, with patience and practice, you too can master it. These basics will get you off to a good start.
1. Dilate properly
To conduct a good peripheral exam, the patient’s eyes must be well dilated. Use both 1% tropicamide and 2.5% phenylephrine for the best dilation. Patients with darker-colored irides may need more than one set. A slit-lamp exam with a 90-diopter (D) lens or an improved digital lens can help identify areas of concern, but it does not replace the dynamic interrogation of the retina with indirect ophthalmoscopy and scleral depression.
2. Position the patient for optimal viewing
Successful indirect ophthalmoscopy depends on proper positioning. Ideally, you want the patient to lay flat in a reclining chair with room for you to move freely around the head. A partially upright position will help the shorter resident see the superior retina, but it will also make it nearly impossible to see the inferior retina.
- When examining the superior retina, “the patient looks up and doctor gets small” (Figure 1 in slideshow below).
- When examining the inferior retina, “the patient looks down and doctor gets tall.” You will find that subtly tilting the head (usually in the direction of gaze) helps improve the view. (See video below.)
3. Choose the right lens
You have two main options for indirect ophthalmoscopy.
20 D: The most commonly used binocular indirect ophthalmoscopy (BIO) lens, the 20-D double aspheric lens has magnification up to 3.13°— and a 60° dynamic field of view. Use the 20-D lens to evaluate macular and peripheral pathology.
28 D: Initially, viewing pathology near the ora serrata is easier with a 28-D lens. The 28-D lens sacrifices some magnification (2.27°—) but offers a larger 69° dynamic field of view.
4. Minimize lens distortion
Because of the lenses’ aspheric nature, you have to hold the lens right-side up to minimize distortions. Move the lens in and out to focus and refine the view. If your hand is large enough, it helps to stabilize the lens with a finger on the patient’s head (Figure 2).
5. Adjust the indirect headset
First, adjust the headband so that the scope is secure on your head.
Then adjust the pupillary distance and height of the beam so you can see a full beam with each eye (Figure 3).
Set the light aperture to the largest spot for a fully dilated patient. Use the smallest aperture for smaller pupils and intraocular gas. The medium light gives an 8-mm-diameter view when in focus with the 20-D lens.
Generally, use the white light filter. A diffuser can improve the field of view and is softer and more comfortable for the patient. Adjust the light intensity to allow yourself a clear view while attempting to make the patient comfortable.
6. Depress the sclera
This allows for dynamic viewing of the retina. Always perform scleral depression for patients with signs and symptoms concerning for retinal tears or detachments (flashes and floaters). The inward curvature of the anterior retina requires you to depress or deform the globe in order to bring the peripheral retina into your field of view. This is referred to as the “bump.” The dynamic exam allows you to elevate retinal breaks and more easily evaluate them. Topical anesthetic can help make the patient more comfortable. Scleral depressors can vary is size and shape. When in a pinch, a cotton-tip applicator works nicely.
7. Ask for help when you need it
When in doubt, ask an attending or senior resident to confirm your exam findings.
Good luck and remember, practice makes perfect.
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About the author: Christopher Nathaniel Roybal, MD, PhD, is in his first year of practice at Eye Associates of New Mexico in Albuquerque and joined the YO Info editorial board in 2017. He completed his vitreoretinal fellowship training at the University of Iowa.