Lectures 11

Question 1

Types of Coloboma

Answer 1

Retinal Coloboma

Macular Coloboma

Optic Nerve Coloboma

Question 2

Coloboma

Answer 2

Defect - a hole in one of the structures of the eye, such as the iris, retina, choroid, or optic disc

Present from birth

Question 3

Closure of the optic fissure

Answer 3

day 33 of gestation

Allows for pressurization of the globe

Question 4

Embryonic fissure development

Answer 4

Develops from eccentric invagination of the optic vesicle leaving a gap INFERONASALLY

This gap allows the hyaloid artery to access the inner eye and is crucial for continued ocular development

Question 5

Closure of the embryonic fissure

Answer 5

Begins at the equator and then proceeds anteriorly and posteriorly

Question 6

Failure of closure or incomplete closure of the embryonic fissure

Answer 6

Results in coloboma of the cornea, iris, ciliary body, choroid, retina and/or optic nerve

Question 7

Choroidal fissure

Answer 7

located on the undersurface of the optic stalk

Permits access into the interior of the developing eye for the precursors of the hyaloid artery and vein

Question 8

Coloboma of the Eyelids

Palpebral Coloomas

Answer 8

Characterized by a small notch in the superior eyelid, but the defect may involve almost the entire lid

Uncommon

Result from local developmental disturbances in the formation/growth of the eyelids

Secondary symptoms: drying, ulceration of the cornea

Question 9

Lens Coloboma

Answer 9

Due to a defective or absent development of the zonules in any segment that causes flattening of the equator of the lens

Due to a lack of tension on the lens capsule and subsequent contraction and notching in that region

Misnomer: no loss of lens tissue; actually effect of coloboma of zonules and/or ciliary body

Question 10

Iris Coloboma

Answer 10

Defect in the inferior sector of the iris or a notch in the pupillary margin, giving the pupil a KEYHOLE appearance

Frequently hereditary (autosomal dominant characteristic)

Question 11

Retinochoroidal Coloboma

Answer 11

Characterized by a localized gap in the retina and choroid, usually inferior to the optic disc

Usually bilateral

Does not cause symptoms

Question 12

Optic Nerve Coloboma

Answer 12

Results from an incomplete closure of the embryonic fissure

Can either be unilateral or bilateral

Often familial

Appearance: white, bowl-shaped excavation on the inferior optic nerve head

• optic disc enlargement
• inferior neuroretinal rim is thin/absent
• superior neuroretinal rim is relatively normal

May involve the choroid and retina

Iris and ciliary colobomas may also be present

Question 13

Cyclopia

Answer 13

Rare anomaly

The eyes are partially or completely fused, forming a single median eye enclosed in a single orbit
(single midline eye)

Cyclopia and Synophthalmia are associated with other craniocerebral defects - incompatible with life

Question 14

Synophthalmia

Answer 14

Fusion of the eyes

Question 15

Microphthalmia

Answer 15

Congenital microphthalmia - heterogenous group of eye defects
-autosomal dominant, autosomal recessive, or x-linked

Most cases - caused by infectious agent (rubella, toxoplasma gondii, herpes simplex virus)

May be very small and associated with other ocular defects, or may be normal-appearing rudimentary eye

Affected side is under developed, orbit is small

• arrested development of the eye before/shortly after the optic vesicle has formed in the fourth week
• lens does not form

Question 16

Anophthalmia

Answer 16

Unilateral or bilateral

Absence of the eye (RARE)

Eyelids form, but no eyeball develops

Formation of the orbit relies on stimulation from the developing eye, so orbit defects are always present

Usually accompanied by other severe craniocerebral defects

Question 17

Congenital Ptosis of Eyelid

Answer 17

Drooping of the superior eyelids at birth (common)

Blepharoptosis may result from failure of normal development of the levator palpebrae superioris muscle

Autosomal dominant

Vision can be affected if the eyelid margin completely or partially occludes pupil - early surgical correction necessary

Question 18

If ptosis is associated with the inability to move the eyeball superiorly…

Answer 18

there is also failure of the superior rectus muscle of the eyeball to develop normally

Question 19

Congenital Aniridia

Answer 19

Rare anomaly

Lack of iris tissue or almost complete absence of the iris

Results from an arrest of the development at the rim of the optic cup during the 8th week

May be associated with glaucoma, cataracts, and other eye abnormalities

May be familial (dominant) or sporadic

Mutation of the Pax6 gene results in aniridia

Question 20

Congenital Aphakia

Answer 20

Absence of the lens is extremely rare and results from failure of the LENS PLACODE to form during the FOURTH WEEK

May also result from failure of lens induction by the OPTIC VESICLE

Question 21

Lens placode formation

Answer 21

4th week of gestation

Question 22

Congenital Cataracts

Answer 22

lens = opaque with frequent grayish-white appearance

without treatment, blindness results

Many are inherited dominantly

Some are caused by teratogenic agents

• rubella
• physical agents (radiation)
• enzymatic deficiency - congenital galactosemia

Question 23

Lens vulnerability to Rubella Virus

Answer 23

4th-7th week of gestation when primary lens fibers are forming

Question 24

Cataracts from congenital galactosemia

Answer 24

Enzyme deficiency cause

Cataracts develop as early as the second week after birth

Because of the enzyme deficiency, large amounts of galactose from milk accumulate in the infants blood and tissues, causing injury to the lens and resulting in Cataract formation

Question 25

Congenital Glaucoma

Answer 25

Usually results from abnormal development of the drainage mechanism of the aqueous humor during the fetal period

Intraocular tension rises because of an imbalance between the production of aqueous humor and its outflow
-this imbalance may result from abnormal development of the scleral venous sinus

Genetically heterogeneous (many different genotypes)

May result from Rubella infection during early pregnancy

Mutations in the CYP1B1 gene are associated with approximately 65% of cases of congenital glaucoma

Question 26

Mutations in the CYP1B1 gene

Answer 26

Associated with ~65% of cases of congenital glaucoma

Question 27

Persistent Hyperplastic Primary Vitreous

Answer 27

The distal part of the hyaloid artery normally degenerates as its proximal part becomes the central artery of the retina
-PHPV = distal part of the hyaloid persisting

May appear freely moving, nonfunctional vessel or worm-like projecting from the optic disc

Sometimes appears as a fine strand traversing the vitreous body

Unusual cases: the entire distal part of the artery persists and extends from the optic disc through the vitreous body to the lens
-microphthalmic eye

Most unilateral and non-hereditary

Bilateral PHPV may follow autosomal recessive or autosomal dominant inheritance

Question 28

Causes/association of bilateral PHPV

Answer 28

Trisomy 13 (Patau syndrome)

Autosomal dominant

Autosomal recessive

Question 29

Persistent Tunica Vasculosa Lentis

Answer 29

Congenital ocular anomolay

Form of PHPV (developmental disorder of the vitreous)

Usually unilateral and first noticed in the neonatal period

May be associated with microphthalmos, cataracts, and increased IOP

Elongated ciliary processes are visible through the dilated pupil

Confirmed by USG B-scan in presence of a cataract

Question 30

Persistent Pupillary Membrane

Answer 30

Remnants of pupillary membrane

May persist as web-like strands of connective tissue or vascular arcades over the pupil in neonates, especially in premature infants

Seldom interferes in vision

VERY RARELY: entire pupillary membrane persists -> congenital atresia of the pupil

Question 31

Pupillary Membrane

Answer 31

Covers the anterior surface of the lens during the embryonic period and most of the fetal period

Question 32

Epicapsular Stars

Answer 32

Tiny, stellate, star-shaped pigmented opacities on the anterior lens capsule

Unilateral or bilateral

Question 33

Remnants of the Tunica Vasculosa Lentis

Answer 33

a vascular network that surrounds the lens during embryogenesis

Epicapsular stars & PPM

Question 34

Bermeister Papilla

Answer 34

Names after Austrian ophthalmologist O. Bergmeister (1845-1918)

At birth, the hyaloid artery regresses, and is normally completely regressed by the time of eyelid opening

Bergmeister’s papilla is a remnant of the hyaloid artery fibrous sheath (a small tuft of fibrous tissue)

Arises from the center fo the optic disc

Frequently observed as an incidental clinical finding

Question 35

Mittendorf’s Dot

Answer 35

A small, circular opacity on the posterior lens capsule

Classically nasal in location

Smal gray or white opacity

Represents the anterior attachment of the hyaloid artery

Question 36

Detachment of the Retina

Answer 36

Occurs when the inner and outer layers of the optic cup fail to fuse during the fetal period to form the retina

Occurs in conjunction with other syndromes (Down’s and Marfan)

Separation of neural and pigment layers of the retina (partial or complete)

May result from unequal rates of growth of the 2 retinal layers

Secondary detachments: occur in association with other defects of the eye/head or trauma

Question 37

Ocular Albinism

Answer 37

Variance in melanocytes that derive their pigment from neural crest

Melanin production is gene regulated

Melanocytes that are neuroectodermal in derivation (retinal pigment, iris, CB) are densely pigmented in all races

Sensory retina development is affected (absent pigment)

Macula underdeveloped, fovea may be absent

Number of rods may be decreased

Abnormal optic nerve projection to LGN (more crossed fibers than normal) producing binocular problems

Question 38

Retinopathy of Prematurity

ROP

Answer 38

Potentially blinding eye disorder that primarily affects premature infants weighing 2 3/4 lbs (1250 grams) or less that are born before 31 weeks gestation

Premature infants who are exposed to a high concentration of oxygen (oxygen chamer)

Complications: neovascular invasion of vitreous, vitreoretinal adhesions, hemorrhage, retinal detachment

Occurs in 4 stages

Question 39

Papilledema

Answer 39

Edema of the Optic Disc

Increase in CSF pressure slows venous return from retina, causing fluid accumulation of the optic disc

Occurs because the retinal vessels are covered with pia mater and lie in the extension of the subarachnoid space that surrounds the optic nerve

Question 40

Tilted ONH

Answer 40

Common in high myopia

ON typically exits sclera at 90˚ angle

Tilted: occurs when nerve exits eye at oblique angle

Typically bilateral in which superiortemporal disc is raised, simulating disc swelling, which the inferiornasal disc is flat or depressed

Thinning of RPE and choroid in the inferior nasal quadrant

Question 41

Optic Nerve Hypoplasia

Answer 41

ONH appears abnormally small due to a low number of axons

The disc may appear gray or pale and is surrounded by a light-colored peripillary hallo

At the normal junction between the sclera and lamina cribosa, there is another change in pigmentation, a “double ring sign,” associated with the hypoplasia

Question 42

Aplasia of the ONH

Answer 42

RARE, congenital developmental anomaly, comprising of absence of ON, central retinal vessels and ganglion cells

Usually accompanied by other central nervous system anomalies, micropthalmous

Often unilateral