Ocular Embryology

gastrulation

process by which a ball of cells rearranges to form 3 germ layers

blastula

ball of cells that goes through gastrulation

endoderm, mesoderm, ectoderm

what are the 3 germ layers formed in gastrulation?

ectoderm

outer germ layer; becomes skin, hair, mammary glands, and nervous system

mesoderm

middle germ layer; becomes skeletal muscle, bones, connective tissue, and heart

endoderm

inner germ layer; becomes digestive tract, lungs, thyroid

primitive streak

what initiates gastrulation?

neural plate

thickening of the ectoderm near the cranial pole forms the _________

neurulation

process by which the presence of notochord induces surface ectoderm to form the neural tube

optic vesicles

optic grooves form what?

E

optic cups

optic vesicles form what?

holoprosencephaly

spectrum of major developmental defects of the brain in which the embryonic forebrain fails to divide into right and left hemispheres, giving rise to midfacial developmental defects

cyclopia

single eye globe with varying degrees of doubling of intrinsic ocular structures and nasal agenesis with a proboscis above the midline eye

optic cup

formed by optic vesicle invaginating to form this; bilayered, hemispherical, formed at day 27

F

surface ectoderm

what are the lens vesicle and lens pit formed from?

A

RPE

what does the outer layer of the optic cup become?

retina

what does the inner layer of the optic cup become?

corneal epithelium

what does the resealed surface ectoderm become once the lens is detached?

anterior myoepithelium, pigmented ciliary epithelium, RPE

the outer layer of the optic cub becomes the _______________ in the iris, the ______________ in the ciliary body, and the ___________ in the retina

posterior pigmented epithelium, nonpigmented ciliary epithelium, neurosensory retina

the inner layer of the optic cup becomes _______________ in the iris, the ______________ in the ciliary body, and the ___________ in the retina

hyaloid vascular system

transient set of arterial and venous vessels

week 8

when does the choroid/optic/hyaloid fissure close?

optic stalk

axons of ganglion cells accumulate in the _____ and form the optic nerve

coloboma

incomplete closure of the optic fissure may affect the developing optic cup or stalk or the adult derivatives; pars plana doesn’t fuse in ciliary body due to abnormal choroidal fissure closure

lens, corneal epithelium

what are the 2 key structures formed by the surface ectoderm?

lens pit

what does the lens placode form?

lens placode

formed by thickening of surface ectoderm close to the vesicle

D

PAX6

gene that directs development of lens placode

cataracts, coloboma

what are 2 congenital abnormalities in the lens?

lenticonus

lens capsule abnormality, can be anterior or posterior, lens takes on a more cone shape

neural ectoderm

what do the sphincter and dilator muscles originate from?

by birth

when are the sphincter and dilator muscles completely developed?

iris cysts

sometimes formed in region of the former marginal sinus following treatment with miotics such as Pilocarpine, arise in same tissue plane as marginal sinus

cystic elevation

congenital malformation of peripheral iris, arises due to defective migration of neural crest cells

aniridia

optic cup does not migrate over anterior surface of the lens and iris does not form

neuroblasts, marginal zone

inner layer of optic cup is divided into these 2 layers

marginal zone

layer of optic cup that is initially anucleate

inner neuroblast zone

the marginal zone becomes the _________

outer neuroblast zone

the neuroblast layer becomes the _________

transient fiber layer of chievitz

nuclear-free zone that is b/t the inner and outer layers of the inner optic cup; not permanent

ganglion, amacrine, Muller

what cells does the inner neuroblastic layer form?

photoreceptor, horizontal, bipolar

what cells does the outer neuroblastic layer form?

ganglion cells

what are the earliest retinal cells formed?

rods, bipolar, Muller

what are the retinal cells that are formed later on in development?

8

by week __ ganglion cells, amacrine cells, and muller cells develop from the inner neuroblastic layer

12

by week __ photoreceptors align along the outside of the inner layer of the optic cup, ganglion cell layer is evident

cones

which photoreceptor develops first?

20

by week __ ganglion cell layer is well established and reduction in retinal cells by apoptosis begins

24

by week __, no mitosis occurs but retinal growth continues by cell differentiation, growth, and maturation

displacement of inner retinal components to form depression

what is the first stage of fovea development

migration of photoreceptors toward the center which increases cone packing

what is the second stage of fovea development?

maturation of photoreceptors

what is the third stage of fovea development?

post birth

when does fovea development finish?

foveola

what is the retinal region last to reach maturity?

area, volume

the RPE increases in ____ but not _____ over time

RPE

what is the first tissue in the body to form melanosome pigment?

neuroectoderm & surface ectoderm

what does the vitreous develop from?

lens capsule

substrate on which incipient hyaloid arterial system grows to transiently nourish the lens through the active phase of growth

10

at ___ weeks, lens has completed major development and hyaloid vasculature begins to regress

primary vitreous

• formation is related to the development of the hyaloid vasculature that enters the developing eye through the fetal fissure

• begins to form thin fibrils that originally connected lens vesicles with inner surface of optic cup

• syncytium through which mesodermal cells condense to form the endothelial linings of the hyaloid vasculature

cloquet canal

funnel shaped structure that encompasses primary vitreous within the region of atrophying hyaloid canal

tertiary vitreous

zonule fibers that develop b/t lens equator and ciliary body

hyaloid artery

• terminal branch of dorsal ophthalmic artery

• forms transient embryonic vascular bed to support the rapid growth of the lens and optic cup until adult ocular vasculature is established

• peak development around week 12 and atrophy begins around week 12

Bergmeister papilla

glial tissue that persists on the nerve head

Mittendorf dot

pin-point remnant of the hyaloid artery on the posterior surface of the lens

persistent hyaloid artery

remnant of hyaloid artery

epicapsular stars

remnants of primary vitreous; seen as small, brown stellate opacities on the anterior surface of the lens

Coat’s disease

congenital peripheral retinal telangiectasis in which abnormally dilated vessels in the retinal periphery leak serum leading to exudative retinal detachment; almost always unilateral

von-Lindau disease

characterized by formation of hemangioblastomas in the retina, CNS, and other organs

retinopathy of prematurity

vessels are tortuous and do not reach temporal retinal periphery forming an ischemic elevated ridge of vascular shunts that secrete pro-angiogenic factors that can contribute to neovascularization and progression of the disease

neural crest

_______ cells give rise to the corneal endothelium, corneal stroma, trabecular meshwork, choroid, orbital fat and CT and extra orbital muscles

unknown

what is Schlemm’s canal derived from?

Axenfeld-Rieger’s syndrome

causes abnormal formation of angle structures and iris, commonly associated with glaucoma

Peter’s anomaly

very severe dysgenesis of angle, iris, and cornea, usually results from delayed or incomplete separation of lens vesicle from surface, leaving a central corneal opacity due to defect in continuity of Descemet’s membrane and corneal endothelium

neural crest mesenchyme

what does the sclera develop from?

surface ectoderm

what do the eyelids originate from?

fuse

eyelids _____ by week 10

re-open

eyelids _______ around week 26

ablepharon/cryptophthalmos

failure of lids to properly form; absence of palpebral fissure and failure of differentiation of eyelid structures

ankyloblepharon

failure of the eyelids to completely separate and otherwise normal formation of the globe and lids

congenital ptosis

autosomal dominant, surgically correctable, disturbed development of the levator palpebrae superiosis and/or its oculomotor innervation

far apart, closer

orbit bones start _____ and move ______

incomplete canalization of nasolacrimal duct

failure to open the nasolacrimal system prior to postpartum onset of tearing initially results in spilling of tears over the lid margin; often monocular in infants

dacryocystitis

open punctum, but valve of Hasner has not yet perforated, causes in stagnant tears resulting in infection

PAX6

what is the master regulator of eye development?

forebrain

C

optic grooves

B

optic vesicle

E

optic stalk

G

lens vesicle

what does the lens pit become?