Chapter 20 Flashcards
may occur if the choroid fissure fails to close.
Coloboma
Normally, the choroid fissure closes during what week?
7th
Cleft persisting when the choroid fissure does not close. Usually in the iris only
Coloboma iridis
Cleft extending into the ciliary body, the retina, the choroid, and the optic nerve.
Coloboma iridis
Gene mutations that have been linked with optic nerve colobomas
PAX2
Renal defects also occur with mutations in PAX2 resulting to
Renal coloboma syndrome
may persist instead of being resorbed during formation of the anterior chamber.
Iridopupillary membrane
cause the lens to become opaque during intrauterine life. Al- though this anomaly is usually genetically determined, many children born to mothers who had rubella [German measles] between the fourth and seventh weeks of pregnancy had cataracts.
Congenital cataracts
If the mother is infected after the seventh week of pregnancy, the lens es- capes damage, but the child may have hear- ing loss as a result of
Cochler abnormalities
This vaccine helped eradicate (nearly) congenital rubella syndrome in the United States.
MMR vaccine
persist to form a cord or cyst. Normally, the distal portion of this vessel degenerates, leaving the proximal part to form the central artery of the retina.
Hyaloid artery
the eye is too small; the eyeball may be only two-thirds of its normal volume. Usually associated with other ocular abnormalities, and can result from intrauterine infections, such as cytomegalovirus and toxoplasmosis.
Microphthalmia
absence of the eye. In some cases, histological analysis reveals some ocular tissue. The defect is usually accompanied by severe cranial abnormalities.
Anophthalmia
absence of the lens
Congenital aphakia
Absence of the iris
aniridia
are rare anomalies that result from disturbances in induction and development of tissues responsible for formation of these structures.
Congenital aphakia and aniridia
True or False.
Mutations in PAX2 result in aniridia and may also contribute to anophthalmia and microphthalmia.
False. PAX6
comprise a spectrum of defects in which the eyes are partially or completely fused
Cyclopia and synophthalmia
Single eye
Cyclopia
Fusion of the eyes
Synophthalmia
Cyclopia and synophthalmi are caused by a loss of midline tissue that may occur as early as days
19 to 21 of gestation
Loss of midline tissue results in underdevelopment of the
forebrain and frontonasal prominence.
The eyes are fused because loss of midline structures prevented the eye fields from separating. Such babies also have severe cranial defects, including holoprosencephaly
Synophthalmia
The eyes are fused because loss of midline structures prevented the eye fields from separating. Such babies also have severe cranial defects, including holoprosencephaly
Synophthalmia
