Normal and Abnormal Fundus Findings in General

Normal fundus: The retina is normally completely transparent without any intrinsic color. It receives its uniform bright red coloration from the vascula-ture of the choroid (Fig. 12.8). The vessels of the choroid themselves are obscured by the retinal pigment epithelium. Loss of transparency of the retina is a sign of an abnormal process (for example in retinal edemas, the retina appears whitish yellow). The optic disk is normally a sharply defined, yellowish orange structure (in teenagers it is pale pink, and in young children significantly paler) that may exhibit a central depression known as the optic or physiologic cup. Light reflection on the inner limiting membrane will normally produce multiple light reflexes on the fundus. Teenagers will also exhibit a normal foveal reflex and wall reflex surrounding the macula, which is caused by the transition from the depression of the macular to the higher level of the retina (Fig. 12.9).

Fluorescein angiography of the fundus.

White light

Light source

Blue filter

Camera b

Yellow-green light reaches the camera

Yellow-green light is emitted; blue light is reflected

Yellow-green light is emitted; blue light is reflected

Fig. 12.7 Blue and yellow-green filters are placed along the optical axis of a single-lens reflex camera. a First the blue filter ensures that only blue light from the light source reaches the retina. This excites the previously injected fluorescein dye in the vessels of the fundus. b The excited fluorescein emits yellow-green light, and the blue light is reflected. The yellow-green filter blocks the blue components of the reflected light so that the camera records only the image of the fluorescent dye.

Yellow-green filter

Fig. 12.7 Blue and yellow-green filters are placed along the optical axis of a single-lens reflex camera. a First the blue filter ensures that only blue light from the light source reaches the retina. This excites the previously injected fluorescein dye in the vessels of the fundus. b The excited fluorescein emits yellow-green light, and the blue light is reflected. The yellow-green filter blocks the blue components of the reflected light so that the camera records only the image of the fluorescent dye.

Normal Fundus Photo
Fig. 12.8 The macula lutea lies about 3-4mm temporal to and slightly below the optic disk. The fundus receives its uniform bright red coloration from the vessels of the choroid. Venous diameter is normally 1.5 times greater than arterial diameter.

— Wall reflex surrounding the macula ■

Age-related changes: The optic disk turns pale yellow with age, and often the optic cup will become shallow and will be surrounded by a region of choroidal atrophy. The fundus will become dull and nonreflective. Drusen will be visible in the retinal pigment epithelium and middle peripheral reticular proliferations of pigment epithelium will be present. The arterioles will be elongated due to loss of elasticity with irregular filling due to thickening of the vascular walls. Meandering of the venules will be present with crossing signs, i.e., the sclerotic artery will be seen to compress the vein at the arteriovenous crossing, reducing the diameter of the column of venous blood. In extreme cases venous blood flow will be cut off completely.

Abnormal changes in the fundus: As a rule, loss of transparency of the retina is a sign of an abnormal process. For example in a retinal edema, the retina appears whitish yellow (see Fig. 12.19). A distinctive feature of abnormal retinal and choroidal changes is that the type and appearance of these changes permit precise topographic localization of the respective abnormal process when the diagnosis is made. The ophthalmoscopic image will usually allow one to determine in which of the layers shown in Fig. 12.2 the process is occurring. For example, in Fig. 12.27 (nonexudative age-related macular degeneration) one may see that the drusen and atrophy are located in the retinal pigment epithelium; the structures above it are not affected, as is apparent from the intact vascular structures.

Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

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Responses

  • senay
    Is the abnormal level for color vision acuity?
    8 months ago

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