VIDEOS IN CLINICAL MEDICINE /Examination of the Retina

Indications

The retinal examination is part of a complete physical examination. It is particularly important in patients with a history of such systemic diseases as diabetes, hypertension, and atherosclerosis. Patients with the human immunodeficiency virus (HIV) or the acquired immunodeficiency syndrome (AIDS) are also at increased risk for retinal diseases. Evaluation of the retina may reveal the initial signs of diabetic retinopathy, hypertensive retinopathy, macular edema, glaucoma, or macular degeneration. Diagnosis and appropriate interventions can help preserve sight and prevent disease progression.2

Indications for urgent direct ophthalmoscopy include a clinical suspicion of increased intracranial pressure, occluded retinal vessels, and retinal detachment. Any of these conditions, or the sudden loss of vision or a change in vision, constitutes an ophthalmic emergency. The patient should be seen by an ophthalmologist immediately or should be sent to the emergency department.

Anatomy

The inner structures of the eye can be visualized through the pupil, the central opening in the iris. The light rays from the ophthalmoscope pass through the cornea, pupil, and lens to focus on the retina, producing an upright, magnified image. The retina is located on the inner surface of the globe, opposite the pupillary opening. The color should appear red, orange, or brown and varies from person to person.

Direct Ophthalmoscopic Settings

The direct ophthalmoscope consists of a handle, which contains the power supply and a light source, and a head, which contains the viewing window and lenses. The on–off switch adjusts the brightness of the light. The apertures include a large circle, a medium circle, a small circle, and a slit beam. To reduce the patient's pupillary constriction it is best to use the ophthalmoscope at a brightness level of 80 to 90%, with the aperture set to the small or medium circle.

The ophthalmoscope contains a range of lenses with positive and negative diopters that compensate for refractive error on the part of the examiner and the patient. If the patient has hyperopia, the retina will be closer to the pupil than normal. If the patient has myopia, the retina will be farther away from the pupil than normal. The lenses are adjusted by turning the dial. Negative numbers focus on objects that are farther away, and positive numbers focus on objects that are closer.

Patient Preparation

Explain the procedure and tell the patient that direct ophthalmoscopy has virtually no risks, although there may be some discomfort caused by the bright light shining into the patient's eyes. Ask the patient to sit, with legs uncrossed. Have the patient remove eyeglasses, if present. Contact lenses will not affect the examination and may be left in place.

Procedure

Darken the room to maximize pupillary dilatation. Designate a point (e.g., a small painting hung on the wall) for the patient to look at that is at least 1 m away from the patient. It is easier to fixate on an image or object than a blank wall. Switch on the ophthalmoscope light, and set the diopters to 0. You may use your contralateral hand to elevate the patient's upper eyelid. Always use your right eye to examine the patient's right eye and your left eye to examine the patient's left eye to avoid being nose to nose with the patient.

Start by locating the red reflex, which is the reflection of light from the retina. Hold the viewing window of the ophthalmoscope directly in front of your eye. Position the ophthalmoscope about 30 cm from the patient's eye, slightly temporal to the center, and shine light into the pupil. A diminished red reflex or the absence of a red reflex could indicate an obstruction (e.g., cataracts).

Follow the red reflex as you gradually move closer to the patient. Turn the dial clockwise to decrease the diopters until you focus on the retina. Hold the ophthalmoscope as close to the patient's eye as possible, since this will optimize your view. You will be able to observe only a small area of the retina in the viewing window. Tilt the ophthalmoscope as needed to visualize different areas. Find and follow a vessel as it increases in caliber, tracing it back to its origin at the optic disk. The optic disk is located approximately 15 degrees nasal to the center of the retina and should appear to be yellowish orange