Figure 1C-67 Assessing the depth of the anterior chamber.
Dense nuclear dominant condition, often with incomplete expression, in which there is increased length of the long bones; ocular complications include dislocation, or subluxation, of the lens, usually superiorly and nasally. Figure 10-70 shows a subluxated lens secondary to Marfan's syndrome. This is the pupil of the patient's left eye. Note the lower edge of the lens and the attached zonules that are apparent from the 3 o'clock to 7 o'clock positions (white lines). The red behind these lines is the red reflex of the retina in the background.
Many patients now receive intraocular lens implants after the removal of a cataractous lens. Figure 10-71 shows a dislocated intraocular lens implant. Note the dislocated wire attachment.
Before the examination of the optic fundus is discussed, a few words about the ophthalmoscope are in order. The ophthalmoscope is an instrument with a mirror optical system for viewing the interior anatomy of the eye. There are two dials on the ophthalmoscope: one adjusts the light apertures and filters, and the other changes the lenses to correct for the refractive errors of both the examiner and the patient.
The most important apertures and filters are the small aperture, the large aperture, and the red-free (green) filter. The small aperture is for an undilated pupil; the large aperture is for a dilated pupil; and the red-free filter excludes rays of red light and is designed for visualization of blood vessels and hemorrhages. With this filter, the retina appears gray, the disc appears white, the macula appears yellow, and blood appears black.
Hold the ophthalmoscope in your right hand in front of your right eye to examine the patient's right eye. Ask the patient to look straight ahead and fixate on a distant target. If you wear glasses, remove them for better visualization of the retina. The ophthalmoscope light is turned on, and the aperture is switched to the small aperture. Start with the lens diopter* dial set to 0 if you do not use glasses. The myopic examiner should start with "minus" lenses, which are indicated by red numbers;the hyperopic examiner needs ''plus'' lenses, which are indicated by black numbers. Your index finger remains on the dial to enable easy focusing.
Place the ophthalmoscope against your forehead while your left thumb gently elevates the patient's right upper eyelid. The ophthalmoscope and your head should function as one unit. While looking through the ophthalmoscope, approach the patient at eye level from about 15 inches (38 cm) away at an angle of about 20° lateral from center, as shown in Figure 10-72. The light should shine on the pupil. A red glow, the red reflex, can be seen in the pupil if the path of light is not obstructed by an opaque lens. Note any opacity in the cornea or lens.
By moving in toward the patient along the same 20° line, you begin to see the blood vessels of the retina. Move in close to the patient, bringing your hand holding the ophthalmoscope against the patient's cheek. As contact is made with the patient, the optic disc
*A unit of optical power of a lens to cause light rays to diverge or converge.
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