Chapter 20

Question 1

may occur if the choroid fissure fails to close.

Answer 1

Coloboma

Question 2

Normally, the choroid fissure closes during what week?

Answer 2

7th

Question 3

Cleft persisting when the choroid fissure does not close. Usually in the iris only

Answer 3

Coloboma iridis

Question 4

Cleft extending into the ciliary body, the retina, the choroid, and the optic nerve.

Answer 4

Coloboma iridis

Question 5

Gene mutations that have been linked with optic nerve colobomas

Answer 5

PAX2

Question 6

Renal defects also occur with mutations in PAX2 resulting to

Answer 6

Renal coloboma syndrome

Question 7

may persist instead of being resorbed during formation of the anterior chamber.

Answer 7

Iridopupillary membrane

Question 8

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.

Answer 8

Congenital cataracts

Question 9

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

Answer 9

Cochler abnormalities

Question 10

This vaccine helped eradicate (nearly) congenital rubella syndrome in the United States.

Answer 10

MMR vaccine

Question 11

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.

Answer 11

Hyaloid artery

Question 12

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.

Answer 12

Microphthalmia

Question 13

absence of the eye. In some cases, histological analysis reveals some ocular tissue. The defect is usually accompanied by severe cranial abnormalities.

Answer 13

Anophthalmia

Question 14

absence of the lens

Answer 14

Congenital aphakia

Question 15

Absence of the iris

Answer 15

aniridia

Question 16

are rare anomalies that result from disturbances in induction and development of tissues responsible for formation of these structures.

Answer 16

Congenital aphakia and aniridia

Question 17

True or False.
Mutations in PAX2 result in aniridia and may also contribute to anophthalmia and microphthalmia.

Answer 17

False. PAX6

Question 18

comprise a spectrum of defects in which the eyes are partially or completely fused

Answer 18

Cyclopia and synophthalmia

Question 19

Single eye

Answer 19

Cyclopia

Question 20

Fusion of the eyes

Answer 20

Synophthalmia

Question 21

Cyclopia and synophthalmi are caused by a loss of midline tissue that may occur as early as days

Answer 21

19 to 21 of gestation

Question 22

Loss of midline tissue results in underdevelopment of the

Answer 22

forebrain and frontonasal prominence.

Question 23

The eyes are fused because loss of midline structures prevented the eye fields from separating. Such babies also have severe cranial defects, including holoprosencephaly

Answer 23

Synophthalmia

Question 24

The eyes are fused because loss of midline structures prevented the eye fields from separating. Such babies also have severe cranial defects, including holoprosencephaly

Answer 24

Synophthalmia