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CHAPTER OUTLINE

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  • OPTICS AND MEDIA

  • RETINA

    • Organization

    • Visual field defects

  • NERVE FIBER LAYER/OPTIC DISC

    • Organization

    • Visual field defects

  • THE CHIASM

    • Organization

    • Visual field defects

  • OVERVIEW OF RETROCHIASMAL DEFECTS

    • Homonymous visual field patterns

    • Congruous versus incongruous

    • Effect on visual acuity

  • OPTIC TRACT

  • LATERAL GENICULATE NUCLEUS

    • Organization

    • Visual field defects

  • OPTIC RADIATIONS

    • Organization

    • Visual field defects

  • OCCIPITAL LOBE

    • Organization

    • Visual field defects

  • KEY POINTS

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INTRODUCTION

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This chapter explores how the organization of the eye and visual system dictates specific, recognizable patterns of visual field loss in disease. The principles to be discussed in this chapter generally apply to all forms of perimetry (eg, confrontation, automated perimetry, Goldmann perimetry, and other methods that were discussed in Chapter 2). In addition to the visual field examples given in this chapter, the reader is encouraged to look at additional examples of automated and Goldmann perimetry (referenced in this chapter) found throughout the book.

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As discussed in Chapter 2, the visual field extends approximately 90° temporally, 60° nasally, 70° superiorly, and 70° inferiorly from the fixation point in each eye (see Figure 2–14). Thus, the area of vision in each eye is roughly oval, with more area temporal to the fixation point than nasal. Although we generally measure and display the visual field one eye at a time, it is important to remember that the visual fields from the right and left eyes actually overlap. Motor systems (discussed in Section III) keep both eyes trained on a common fixation point. Therefore, there is binocular representation of the visual field for 60° to the right and left of a common fixation point. Note that the most temporal portion of the visual field from 60° to 90° is seen by only one eye (Figure 3–1). This area of the visual field is known as the temporal crescent.

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Figure 3–1.
Superimposed visual fields.

The visual fields from the right and left eyes overlap with binocular viewing. The area from 60° to 90° in the temporal field of each eye is seen only by one eye (the temporal crescent). Note the position of the blind spot for each eye (L = blind spot of left eye, R = blind spot of right eye).

Graphic Jump Location
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The afferent visual system includes the eyes (optics, media, and retina), optic nerves, chiasm, optic tracts, lateral geniculate nuclei, optic radiations, and visual (occipital) cortex (Figure 3–2). Visual information is transmitted by bundles of axons that represent specific portions of the visual field. The axonal wiring diagram seems complex on the surface, but actually follows a logical design.

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Figure 3–2.
Afferent visual system.

The major components of the afferent visual system are identified. The inset shows the relative position of the visual system in the brain.

Graphic Jump Location

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