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In Depth Tutorials and Information
CHAPTER
31
Osteogen esis Imperfecta an d the Eye
Felix Y. Chau 1 , Dana Wallace 2 , Thasarat Vajaranant 1 , Leon
Herndon 2 , Paul Lee 3 , Pratap Challa 2 , Rand Allingham 2 and Irene
Maumenee 1
1 University of Illinois at Chicago, Illinois Eye and Ear Infirmary, Chicago, IL, USA, 2 Duke University
Eye Center, Durham, NC, USA, 3 University of Michigan, Kellogg Eye Center, Ann Arbor, MI, USA
BASIC EYE AND VISUAL SYSTEM
BACKGROUND
of extraocular muscles. The pupil (central opening of the
iris) reacts to light through the action of pathways from
the retina, brain and ultimately sphincter muscles in the
iris, thus controlling the amount of light entering the eye.
Figure 31.1 shows an overall schematic of the eye.
Overview
The visual system begins with the eye itself and ends
with neurologic functions of the brain. The globe of the
eye can be divided into anterior and posterior compart-
ments. The anterior chamber of the eye is bordered by
the cornea anteriorly and the iris posteriorly and is filled
with aqueous humor, the circulating fluid within the
eye (see Figure 31.1 ). The posterior chamber is bordered
by the iris anteriorly and the lens and anterior vitreous
humor face posteriorly. Light enters the eye through the
clear cornea and then travels through the aqueous humor,
the lens and vitreous humor to reach the retina. Seventy-
four percent of the refractive power of the eye - about 43
diopters - is based on the curvature and refractive index
of the cornea. The other 26% of the refractive power of
the eye - about 15 diopters - is contributed by the lens.
These structures focus light and create formed images on
the retina. The images are converted into intracellular and
intercellular chemical signals by the photoreceptors of the
retina. These chemical signals are translated into neuronal
signals that are transmitted from the retina through the
optic nerve and to the occipital cortex where the signals
are ultimately processed for and used in visual interpre-
tation. The eye is maintained at physiologic pressure by
the internal production of aqueous humor by the ciliary
body. Aqueous humor lows from the posterior to the
anterior chamber and ultimately drains through struc-
tures located in the angle formed by the iris and cornea
called the trabecular meshwork. The eye moves by means
Sclera
The sclera is the opaque white wall of the eye that
encloses the posterior four-fifths of the globe surface. It
Cornea
Anterior chamber
Iris
Anterior chamber angle
Posterior chamber
Ciliary body
Zonules
Ora serrata
3.15 mm
Lens
Lens capsule
24 mm
Vitreous cavity
Neural retina
Choroid
Sclera
Optic disc
Optic nerve
FIGURE 31.1
Schematic of the eye.
 
 
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